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Synthetic-aperture radar

Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide finer spatial resolution than conventional stationary beam-scanning radars. SAR is typically mounted on a moving platform, such as an aircraft or spacecraft, and has its origins in an advanced form of side looking airborne radar (SLAR). The distance the SAR device travels over a target during the period when the target scene is illuminated creates the large synthetic antenna aperture (the size of the antenna). Typically, the larger the aperture, the higher the image resolution will be, regardless of whether the aperture is physical (a large antenna) or synthetic (a moving antenna) – this allows SAR to create high-resolution images with comparatively small physical antennas. For a fixed antenna size and orientation, objects which are further away remain illuminated longer – therefore SAR has the property of creating larger synthetic apertures for more distant objects, which results in a consistent spatial resolution over a range of viewing distances.

To create a SAR image, successive pulses of radio waves are transmitted to "illuminate" a target scene, and the echo of each pulse is received and recorded. The pulses are transmitted and the echoes received using a single beam-forming antenna, with wavelengths of a meter down to several millimeters. As the SAR device on board the aircraft or spacecraft moves, the antenna location relative to the target changes with time. Signal processing of the successive recorded radar echoes allows the combining of the recordings from these multiple antenna positions. This process forms the synthetic antenna aperture and allows the creation of higher-resolution images than would otherwise be possible with a given physical antenna.

Motivation and applications
SAR is capable of high-resolution remote sensing, independent of flight altitude, and independent of weather, as SAR can select frequencies to avoid weather-caused signal attenuation. SAR has day and night imaging capability as illumination is provided by the SAR.

SAR images have wide applications in remote sensing and mapping of surfaces of the Earth and other planets. Applications of SAR are numerous. Examples include topography, oceanography, glaciology, geology (for example, terrain discrimination and subsurface imaging). SAR can also be used in forestry to determine forest height, biomass, and deforestation. Volcano and earthquake monitoring use differential interferometry. SAR can also be applied for monitoring civil infrastructure stability such as bridges. SAR is useful in environment monitoring such as oil spills, flooding, urban growth, military surveillance: including strategic policy and tactical assessment. SAR can be implemented as inverse SAR by observing a moving target over a substantial time with a stationary antenna.

Basic principle
A synthetic-aperture radar is an imaging radar mounted on a moving platform. Electromagnetic waves are transmitted sequentially, the echoes are collected and the system electronics digitizes and stores the data for subsequent processing. As transmission and reception occur at different times, they map to different small positions. The well ordered combination of the received signals builds a virtual aperture that is much longer than the physical antenna width. That is the source of the term "synthetic aperture," giving it the property of an imaging radar. The range direction is perpendicular to the flight track and perpendicular to the azimuth direction, which is also known as the along-track direction because it is in line with the position of the object within the antenna's field of view.

The 3D processing is done in two stages. The azimuth and range direction are focused for the generation of 2D (azimuth-range) high-resolution images, after which a digital elevation model (DEM) is used to measure the phase differences between complex images, which is determined from different look angles to recover the height information. This height information, along with the azimuth-range coordinates provided by 2-D SAR focusing, gives the third dimension, which is the elevation. The first step requires only standard processing algorithms, for the second step, additional pre-processing such as image co-registration and phase calibration is used.

In addition, multiple baselines can be used to extend 3D imaging to the time dimension. 4D and multi-D SAR imaging allows imaging of complex scenarios, such as urban areas, and has improved performance with respect to classical interferometric techniques such as persistent scatterer interferometry (PSI).

Algorithm
SAR algorithms model the scene as a set of point targets that do not interact with each other (the Born approximation).

While the details of various SAR algorithms differ, SAR processing in each case is the application of a matched filter to the raw data, for each pixel in the output image, where the matched filter coefficients are the response from a single isolated point target. In the early days of SAR processing, the raw data was recorded on film and the postprocessing by matched filter was implemented optically using lenses of conical, cylindrical and spherical shape. The Range-Doppler algorithm is an example of a more recent approach.

Existing spectral estimation approaches
Synthetic-aperture radar determines the 3D reflectivity from measured SAR data. It is basically a spectrum estimation, because for a specific cell of an image, the complex-value SAR measurements of the SAR image stack are a sampled version of the Fourier transform of reflectivity in elevation direction, but the Fourier transform is irregular. Thus the spectral estimation techniques are used to improve the resolution and reduce speckle compared to the results of conventional Fourier transform SAR imaging techniques.

FFT
FFT (Fast Fourier Transform i.e., periodogram or matched filter) is one such method, which is used in majority of the spectral estimation algorithms, and there are many fast algorithms for computing the multidimensional discrete Fourier transform. Computational Kronecker-core array algebra is a popular algorithm used as new variant of FFT algorithms for the processing in multidimensional synthetic-aperture radar (SAR) systems. This algorithm uses a study of theoretical properties of input/output data indexing sets and groups of permutations.

A branch of finite multi-dimensional linear algebra is used to identify similarities and differences among various FFT algorithm variants and to create new variants. Each multidimensional DFT computation is expressed in matrix form. The multidimensional DFT matrix, in turn, is disintegrated into a set of factors, called functional primitives, which are individually identified with an underlying software/hardware computational design.

The FFT implementation is essentially a realization of the mapping of the mathematical framework through generation of the variants and executing matrix operations. The performance of this implementation may vary from machine to machine, and the objective is to identify on which machine it performs best.

Advantages

 * Additive group-theoretic properties of multidimensional input/output indexing sets are used for the mathematical formulations, therefore, it is easier to identify mapping between computing structures and mathematical expressions, thus, better than conventional methods.
 * The language of CKA algebra helps the application developer in understanding which are the more computational efficient FFT variants thus reducing the computational effort and improve their implementation time.

Disadvantages

 * FFT cannot separate sinusoids close in frequency. If the periodicity of the data does not match FFT, edge effects are seen.

Capon method
The Capon spectral method, also called the minimum-variance method, is a multidimensional array-processing technique. It is a nonparametric covariance-based method, which uses an adaptive matched-filterbank approach and follows two main steps:
 * 1) Passing the data through a 2D bandpass filter with varying center frequencies ($$\omega_1, \omega_2$$).
 * 2) Estimating the power at ($$\omega_1, \omega_2$$) for all $$\omega_1 \in [0, 2\pi), \omega_2 \in [0, 2\pi)$$ of interest from the filtered data.

The adaptive Capon bandpass filter is designed to minimize the power of the filter output, as well as pass the frequencies ($$\omega_1, \omega_2$$) without any attenuation, i.e., to satisfy, for each ($$\omega_1, \omega_2$$),

 * $$\min_h h^*_{\omega_1,\omega_2} Rh_{\omega_1,\omega_2}$$ subject to $$h^*_{\omega_1,\omega_2} a_{\omega_1,\omega_2} = 1,$$

where R is the covariance matrix, $$h^*_{\omega_1,\omega_2}$$ is the complex conjugate transpose of the impulse response of the FIR filter, $$a_{\omega_1,\omega_2}$$ is the 2D Fourier vector, defined as $$a_{\omega_1,\omega_2} \triangleq a_{\omega_1} \otimes a_{\omega_2}$$, $$\otimes$$ denotes Kronecker product.

Therefore, it passes a 2D sinusoid at a given frequency without distortion while minimizing the variance of the noise of the resulting image. The purpose is to compute the spectral estimate efficiently.

Spectral estimate is given as

 * $$S_{\omega_1,\omega_2} = \frac{1}{a_{\omega_1,\omega_2}^* R^{-1} a_{\omega_1,\omega_2}},$$

where R is the covariance matrix, and $$a^*_{\omega_1,\omega_2}$$ is the 2D complex-conjugate transpose of the Fourier vector. The computation of this equation over all frequencies is time-consuming. It is seen that the forward–backward Capon estimator yields better estimation than the forward-only classical capon approach. The main reason behind this is that while the forward–backward Capon uses both the forward and backward data vectors to obtain the estimate of the covariance matrix, the forward-only Capon uses only the forward data vectors to estimate the covariance matrix.

Advantages

 * Capon can yield more accurate spectral estimates with much lower sidelobes and narrower spectral peaks than the fast Fourier transform (FFT) method.
 * Capon method can provide much better resolution.

Disadvantages

 * Implementation requires computation of two intensive tasks: inversion of the covariance matrix R and multiplication by the $$a_{\omega_1,\omega_2}$$ matrix, which has to be done for each point $$\left(\omega_1, \omega_2\right)$$.

APES method
The APES (amplitude and phase estimation) method is also a matched-filter-bank method, which assumes that the phase history data is a sum of 2D sinusoids in noise.

APES spectral estimator has 2-step filtering interpretation:
 * 1) Passing data through a bank of FIR bandpass filters with varying center frequency $$\omega$$.
 * 2) Obtaining the spectrum estimate for $$\omega \in [0, 2\pi)$$ from the filtered data.

Empirically, the APES method results in wider spectral peaks than the Capon method, but more accurate spectral estimates for amplitude in SAR. In the Capon method, although the spectral peaks are narrower than the APES, the sidelobes are higher than that for the APES. As a result, the estimate for the amplitude is expected to be less accurate for the Capon method than for the APES method. The APES method requires about 1.5 times more computation than the Capon method.

Advantages

 * Filtering reduces the number of available samples, but when it is designed tactically, the increase in signal-to-noise ratio (SNR) in the filtered data will compensate this reduction, and the amplitude of a sinusoidal component with frequency $$\omega$$ can be estimated more accurately from the filtered data than from the original signal.

Disadvantages

 * The autocovariance matrix is much larger in 2D than in 1D, therefore it is limited by memory available.

SAMV method
SAMV method is a parameter-free sparse signal reconstruction based algorithm. It achieves super-resolution and is robust to highly correlated signals. The name emphasizes its basis on the asymptotically minimum variance (AMV) criterion. It is a powerful tool for the recovery of both the amplitude and frequency characteristics of multiple highly correlated sources in challenging environment (e.g., limited number of snapshots, low signal-to-noise ratio. Applications include synthetic-aperture radar imaging and various source localization.

Advantages
SAMV method is capable of achieving resolution higher than some established parametric methods, e.g., MUSIC, especially with highly correlated signals.

Disadvantages
Computational complexity of the SAMV method is higher due to its iterative procedure.

Eigenvector method
This subspace decomposition method separates the eigenvectors of the autocovariance matrix into those corresponding to signals and to clutter. The amplitude of the image at a point ($$\omega_x, \omega_y$$ ) is given by:

\hat{\phi}_{EV}\left(\omega_x, \omega_y\right) = \frac{1} {W^\mathsf{H}\left(\omega_x, \omega_y\right) \left(\sum_\text{clutter} \frac{1}{\lambda_i} \underline{v_i}\,\underline{v_i}^\mathsf{H}\right) W\left(\omega_x, \omega_y\right)}$$

where $$\hat{\phi}_{EV}$$ is the amplitude of the image at a point $$\left(\omega_x, \omega_y\right)$$, $$\underline{v_i}$$is the coherency matrix and $$\underline{v_i}^\mathsf{H}$$ is the Hermitian of the coherency matrix,$$\frac{1}{\lambda_i}$$ is the inverse of the eigenvalues of the clutter subspace, $$W\left(\omega_x, \omega_y\right)$$ are vectors defined as

W\left(\omega_x, \omega_y\right) = \left[1 \exp\left(-j\omega_x\right) \ldots \exp\left(-j(M - 1)\omega_x\right)\right] \otimes \left[1 \exp\left(-j\omega_y\right) \ldots \exp\left(-j(M - 1)\omega_y\right)\right]$$

where ⊗ denotes the Kronecker product of the two vectors.

Advantages

 * Shows features of image more accurately.

Disadvantages

 * High computational complexity.

MUSIC method
MUSIC detects frequencies in a signal by performing an eigen decomposition on the covariance matrix of a data vector of the samples obtained from the samples of the received signal. When all of the eigenvectors are included in the clutter subspace (model order = 0) the EV method becomes identical to the Capon method. Thus the determination of model order is critical to operation of the EV method. The eigenvalue of the R matrix decides whether its corresponding eigenvector corresponds to the clutter or to the signal subspace.

The MUSIC method is considered to be a poor performer in SAR applications. This method uses a constant instead of the clutter subspace.

In this method, the denominator is equated to zero when a sinusoidal signal corresponding to a point in the SAR image is in alignment to one of the signal subspace eigenvectors which is the peak in image estimate. Thus this method does not accurately represent the scattering intensity at each point, but show the particular points of the image.

Advantages

 * MUSIC whitens or equalizes, the clutter eigenvalues.

Disadvantages

 * Resolution loss due to the averaging operation.

Backprojection algorithm
Backprojection Algorithm has two methods: Time-domain Backprojection and Frequency-domain Backprojection. The time-domain Backprojection has more advantages over frequency-domain and thus, is more preferred. The time-domain Backprojection forms images or spectrums by matching the data acquired from the radar and as per what it expects to receive. It can be considered as an ideal matched-filter for synthetic-aperture radar. There is no need of having a different motion compensation step due to its quality of handling non-ideal motion/sampling. It can also be used for various imaging geometries.

Advantages

 * It is invariant to the imaging mode: which means, that it uses the same algorithm irrespective of the imaging mode present, whereas, frequency domain methods require changes depending on the mode and geometry.
 * Ambiguous azimuth aliasing usually occurs when the Nyquist spatial sampling requirements are exceeded by frequencies. Unambiguous aliasing occurs in squinted geometries where the signal bandwidth does not exceed the sampling limits, but has undergone "spectral wrapping." Backprojection Algorithm does not get affected by any such kind of aliasing effects.
 * It matches the space/time filter: uses the information about the imaging geometry, to produce a pixel-by-pixel varying matched filter to approximate the expected return signal. This usually yields antenna gain compensation.
 * With reference to the previous advantage, the back projection algorithm compensates for the motion. This becomes an advantage at areas having low altitudes.

Disadvantages

 * The computational expense is more for Backprojection algorithm as compared to other frequency domain methods.
 * It requires very precise knowledge of imaging geometry.

Application: geosynchronous orbit synthetic-aperture radar (GEO-SAR)
In GEO-SAR, to focus specially on the relative moving track, the backprojection algorithm works very well. It uses the concept of Azimuth Processing in the time domain. For the satellite-ground geometry, GEO-SAR plays a significant role.

The procedure of this concept is elaborated as follows.
 * 1) The raw data acquired is segmented or drawn into sub-apertures for simplification of speedy conduction of procedure.
 * 2) The range of the data is then compressed, using the concept of "Matched Filtering" for every segment/sub-aperture created. It is given by-$s(t, \tau) = \exp \left(-j \cdot \frac{4\pi}{\lambda} \cdot R(t)\right) \cdot \operatorname{sinc}\left(\tau - \frac{2}{c} \cdot R(t)\right)$  where τ is the range time, t is the azimuthal time, λ is the wavelength, c is the speed of light.
 * 3) Accuracy in the "Range Migration Curve" is achieved by range interpolation.
 * 4) The pixel locations of the ground in the image is dependent on the satellite–ground geometry model. Grid-division is now done as per the azimuth time.
 * 5) Calculations for the "slant range" (range between the antenna's phase center and the point on the ground) are done for every azimuth time using coordinate transformations.
 * 6) Azimuth Compression is done after the previous step.
 * 7) Step 5 and 6 are repeated for every pixel, to cover every pixel, and conduct the procedure on every sub-aperture.
 * 8) Lastly, all the sub-apertures of the image created throughout, are superimposed onto each other and the ultimate HD image is generated.

Comparison between the algorithms
Capon and APES can yield more accurate spectral estimates with much lower sidelobes and more narrow spectral peaks than the fast Fourier transform (FFT) method, which is also a special case of the FIR filtering approaches. It is seen that although the APES algorithm gives slightly wider spectral peaks than the Capon method, the former yields more accurate overall spectral estimates than the latter and the FFT method.

FFT method is fast and simple but have larger sidelobes. Capon has high resolution but high computational complexity. EV also has high resolution and high computational complexity. APES has higher resolution, faster than capon and EV but high computational complexity.

MUSIC method is not generally suitable for SAR imaging, as whitening the clutter eigenvalues destroys the spatial inhomogeneities associated with terrain clutter or other diffuse scattering in SAR imagery. But it offers higher frequency resolution in the resulting power spectral density (PSD) than the fast Fourier transform (FFT)-based methods.

The backprojection algorithm is computationally expensive. It is specifically attractive for sensors that are wideband, wide-angle, and/or have long coherent apertures with substantial off-track motion.

Multistatic operation
SAR requires that echo captures be taken at multiple antenna positions. The more captures taken (at different antenna locations) the more reliable the target characterization.

Multiple captures can be obtained by moving a single antenna to different locations, by placing multiple stationary antennas at different locations, or combinations thereof.

The advantage of a single moving antenna is that it can be easily placed in any number of positions to provide any number of monostatic waveforms. For example, an antenna mounted on an airplane takes many captures per second as the plane travels.

The principal advantages of multiple static antennas are that a moving target can be characterized (assuming the capture electronics are fast enough), that no vehicle or motion machinery is necessary, and that antenna positions need not be derived from other, sometimes unreliable, information. (One problem with SAR aboard an airplane is knowing precise antenna positions as the plane travels).

For multiple static antennas, all combinations of monostatic and multistatic radar waveform captures are possible. Note, however, that it is not advantageous to capture a waveform for each of both transmission directions for a given pair of antennas, because those waveforms will be identical. When multiple static antennas are used, the total number of unique echo waveforms that can be captured is

 * $$\frac{N^2 + N}{2}$$

where N is the number of unique antenna positions.

Stripmap mode airborne SAR
The antenna stays in a fixed position. It may be orthogonal to the flight path, or it may be squinted slightly forward or backward.

When the antenna aperture travels along the flight path, a signal is transmitted at a rate equal to the pulse repetition frequency (PRF). The lower boundary of the PRF is determined by the Doppler bandwidth of the radar. The backscatter of each of these signals is commutatively added on a pixel-by-pixel basis to attain the fine azimuth resolution desired in radar imagery.

Spotlight mode SAR
The spotlight synthetic aperture is given by

 * $$Lsa = r_0 \Delta\theta_a$$

where $$\Delta\theta_a$$ is the angle formed between the beginning and end of the imaging, as shown in the diagram of spotlight imaging and $$r_0$$ is the range distance.

The spotlight mode gives better resolution albeit for a smaller ground patch. In this mode, the illuminating radar beam is steered continually as the aircraft moves, so that it illuminates the same patch over a longer period of time. This mode is not a traditional continuous-strip imaging mode; however, it has high azimuth resolution. A technical explanation of spotlight SAR from first principles is offered in.

Scan mode SAR
While operating as a scan mode SAR, the antenna beam sweeps periodically and thus cover much larger area than the spotlight and stripmap modes. However, the azimuth resolution become much lower than the stripmap mode due to the decreased azimuth bandwidth. Clearly there is a balance achieved between the azimuth resolution and the scan area of SAR. Here, the synthetic aperture is shared between the sub swaths, and it is not in direct contact within one subswath. Mosaic operation is required in azimuth and range directions to join the azimuth bursts and the range sub-swaths.

 * ScanSAR makes the swath beam huge.
 * The azimuth signal has many bursts.
 * The azimuth resolution is limited due to the burst duration.
 * Each target contains varied frequencies which completely depends on where the azimuth is present.

Polarimetry
Radar waves have a polarization. Different materials reflect radar waves with different intensities, but anisotropic materials such as grass often reflect different polarizations with different intensities. Some materials will also convert one polarization into another. By emitting a mixture of polarizations and using receiving antennas with a specific polarization, several images can be collected from the same series of pulses. Frequently three such RX-TX polarizations (HH-pol, VV-pol, VH-pol) are used as the three color channels in a synthesized image. This is what has been done in the picture at right. Interpretation of the resulting colors requires significant testing of known materials.

New developments in polarimetry include using the changes in the random polarization returns of some surfaces (such as grass or sand) and between two images of the same location at different times to determine where changes not visible to optical systems occurred. Examples include subterranean tunneling or paths of vehicles driving through the area being imaged. Enhanced SAR sea oil slick observation has been developed by appropriate physical modelling and use of fully polarimetric and dual-polarimetric measurements.

SAR polarimetry
SAR polarimetry is a technique used for deriving qualitative and quantitative physical information for land, snow and ice, ocean and urban applications based on the measurement and exploration of the polarimetric properties of man-made and natural scatterers. Terrain and land use classification is one of the most important applications of polarimetric synthetic-aperture radar (PolSAR).

SAR polarimetry uses a scattering matrix (S) to identify the scattering behavior of objects after an interaction with electromagnetic wave. The matrix is represented by a combination of horizontal and vertical polarization states of transmitted and received signals.

$$S = \begin{bmatrix} S_{HH} & S_{HV} \\ S_{VH} & S_{VV} \end{bmatrix}$$

where, HH is for horizontal transmit and horizontal receive, VV is for vertical transmit and vertical receive, HV is for horizontal transmit and vertical receive, and VH – for vertical transmit and horizontal receive.

The first two of these polarization combinations are referred to as like-polarized (or co-polarized), because the transmit and receive polarizations are the same. The last two combinations are referred to as cross-polarized because the transmit and receive polarizations are orthogonal to one another.

Three-component scattering power model
The three-component scattering power model by Freeman and Durden is successfully used for the decomposition of a PolSAR image, applying the reflection symmetry condition using covariance matrix. The method is based on simple physical scattering mechanisms (surface scattering, double-bounce scattering, and volume scattering). The advantage of this scattering model is that it is simple and easy to implement for image processing. There are 2 major approaches for a 3$$\times$$3 polarimetric matrix decomposition. One is the lexicographic covariance matrix approach based on physically measurable parameters, and the other is the Pauli decomposition which is a coherent decomposition matrix. It represents all the polarimetric information in a single SAR image. The polarimetric information of [S] could be represented by the combination of the intensities $$|S_{HH}|^2, |S_{VV}|^2 , 2|S_{HV}|^2$$ in a single RGB image where all the previous intensities will be coded as a color channel.

Four-component scattering power model
For PolSAR image analysis, there can be cases where reflection symmetry condition does not hold. In those cases a four-component scattering model can be used to decompose polarimetric synthetic-aperture radar (SAR) images. This approach deals with the non-reflection symmetric scattering case. It includes and extends the three-component decomposition method introduced by Freeman and Durden to a fourth component by adding the helix scattering power. This helix power term generally appears in complex urban area but disappears for a natural distributed scatterer.

There is also an improved method using the four-component decomposition algorithm, which was introduced for the general polSAR data image analyses. The SAR data is first filtered which is known as speckle reduction, then each pixel is decomposed by four-component model to determine the surface scattering power ($$P_{s}$$), double-bounce scattering power ($$P_{d}$$), volume scattering power ($$P_{v}$$), and helix scattering power ($$P_{c}$$). The pixels are then divided into 5 classes (surface, double-bounce, volume, helix, and mixed pixels) classified with respect to maximum powers. A mixed category is added for the pixels having two or three equal dominant scattering powers after computation. The process continues as the pixels in all these categories are divided in 20 small clutter approximately of same number of pixels and merged as desirable, this is called cluster merging. They are iteratively classified and then automatically color is delivered to each class. The summarization of this algorithm leads to an understanding that, brown colors denotes the surface scattering classes, red colors for double-bounce scattering classes, green colors for volume scattering classes, and blue colors for helix scattering classes.

Although this method is aimed for non-reflection case, it automatically includes the reflection symmetry condition, therefore in can be used as a general case. It also preserves the scattering characteristics by taking the mixed scattering category into account therefore proving to be a better algorithm.

Interferometry
Rather than discarding the phase data, information can be extracted from it. If two observations of the same terrain from very similar positions are available, aperture synthesis can be performed to provide the resolution performance which would be given by a radar system with dimensions equal to the separation of the two measurements. This technique is called interferometric SAR or InSAR.

If the two samples are obtained simultaneously (perhaps by placing two antennas on the same aircraft, some distance apart), then any phase difference will contain information about the angle from which the radar echo returned. Combining this with the distance information, one can determine the position in three dimensions of the image pixel. In other words, one can extract terrain altitude as well as radar reflectivity, producing a digital elevation model (DEM) with a single airplane pass. One aircraft application at the Canada Centre for Remote Sensing produced digital elevation maps with a resolution of 5 m and altitude errors also about 5 m. Interferometry was used to map many regions of the Earth's surface with unprecedented accuracy using data from the Shuttle Radar Topography Mission.

If the two samples are separated in time, perhaps from two flights over the same terrain, then there are two possible sources of phase shift. The first is terrain altitude, as discussed above. The second is terrain motion: if the terrain has shifted between observations, it will return a different phase. The amount of shift required to cause a significant phase difference is on the order of the wavelength used. This means that if the terrain shifts by centimeters, it can be seen in the resulting image (a digital elevation map must be available to separate the two kinds of phase difference; a third pass may be necessary to produce one).

This second method offers a powerful tool in geology and geography. Glacier flow can be mapped with two passes. Maps showing the land deformation after a minor earthquake or after a volcanic eruption (showing the shrinkage of the whole volcano by several centimeters) have been published.

Differential interferometry
Differential interferometry (D-InSAR) requires taking at least two images with addition of a DEM. The DEM can be either produced by GPS measurements or could be generated by interferometry as long as the time between acquisition of the image pairs is short, which guarantees minimal distortion of the image of the target surface. In principle, 3 images of the ground area with similar image acquisition geometry is often adequate for D-InSar. The principle for detecting ground movement is quite simple. One interferogram is created from the first two images; this is also called the reference interferogram or topographical interferogram. A second interferogram is created that captures topography + distortion. Subtracting the latter from the reference interferogram can reveal differential fringes, indicating movement. The described 3 image D-InSAR generation technique is called 3-pass or double-difference method.

Differential fringes which remain as fringes in the differential interferogram are a result of SAR range changes of any displaced point on the ground from one interferogram to the next. In the differential interferogram, each fringe is directly proportional to the SAR wavelength, which is about 5.6 cm for ERS and RADARSAT single phase cycle. Surface displacement away from the satellite look direction causes an increase in path (translating to phase) difference. Since the signal travels from the SAR antenna to the target and back again, the measured displacement is twice the unit of wavelength. This means in differential interferometry one fringe cycle −$\pi$ to +π or one wavelength corresponds to a displacement relative to SAR antenna of only half wavelength (2.8 cm). There are various publications on measuring subsidence movement, slope stability analysis, landslide, glacier movement, etc. tooling D-InSAR. Further advancement to this technique whereby differential interferometry from satellite SAR ascending pass and descending pass can be used to estimate 3-D ground movement. Research in this area has shown accurate measurements of 3-D ground movement with accuracies comparable to GPS based measurements can be achieved.

Tomo-SAR
SAR Tomography is a subfield of a concept named as multi-baseline interferometry. It has been developed to give a 3D exposure to the imaging, which uses the beam formation concept. It can be used when the use demands a focused phase concern between the magnitude and the phase components of the SAR data, during information retrieval. One of the major advantages of Tomo-SAR is that it can separate out the parameters which get scattered, irrespective of how different their motions are. On using Tomo-SAR with differential interferometry, a new combination named "differential tomography" (Diff-Tomo) is developed.

Tomo-SAR has an application based on radar imaging, which is the depiction of Ice Volume and Forest Temporal Coherence (Temporal coherence describes the correlation between waves observed at different moments in time).

Ultra-wideband SAR
Conventional radar systems emit bursts of radio energy with a fairly narrow range of frequencies. A narrow-band channel, by definition, does not allow rapid changes in modulation. Since it is the change in a received signal that reveals the time of arrival of the signal (obviously an unchanging signal would reveal nothing about "when" it reflected from the target), a signal with only a slow change in modulation cannot reveal the distance to the target as well as a signal with a quick change in modulation.

Ultra-wideband (UWB) refers to any radio transmission that uses a very large bandwidth – which is the same as saying it uses very rapid changes in modulation. Although there is no set bandwidth value that qualifies a signal as "UWB", systems using bandwidths greater than a sizable portion of the center frequency (typically about ten percent, or so) are most often called "UWB" systems. A typical UWB system might use a bandwidth of one-third to one-half of its center frequency. For example, some systems use a bandwidth of about 1 GHz centered around 3 GHz.

The two most common methods to increase signal bandwidth used in UWB radar, including SAR, are very short pulses and high-bandwidth chirping. A general description of chirping appears elsewhere in this article. The bandwidth of a chirped system can be as narrow or as wide as the designers desire. Pulse-based UWB systems, being the more common method associated with the term "UWB radar", are described here.

A pulse-based radar system transmits very short pulses of electromagnetic energy, typically only a few waves or less. A very short pulse is, of course, a very rapidly changing signal, and thus occupies a very wide bandwidth. This allows far more accurate measurement of distance, and thus resolution.

The main disadvantage of pulse-based UWB SAR is that the transmitting and receiving front-end electronics are difficult to design for high-power applications. Specifically, the transmit duty cycle is so exceptionally low and pulse time so exceptionally short, that the electronics must be capable of extremely high instantaneous power to rival the average power of conventional radars. (Although it is true that UWB provides a notable gain in channel capacity over a narrow band signal because of the relationship of bandwidth in the Shannon–Hartley theorem and because the low receive duty cycle receives less noise, increasing the signal-to-noise ratio, there is still a notable disparity in link budget because conventional radar might be several orders of magnitude more powerful than a typical pulse-based radar.) So pulse-based UWB SAR is typically used in applications requiring average power levels in the microwatt or milliwatt range, and thus is used for scanning smaller, nearer target areas (several tens of meters), or in cases where lengthy integration (over a span of minutes) of the received signal is possible. However, that this limitation is solved in chirped UWB radar systems.

The principal advantages of UWB radar are better resolution (a few millimeters using commercial off-the-shelf electronics) and more spectral information of target reflectivity.

Doppler-beam sharpening
Doppler Beam Sharpening commonly refers to the method of processing unfocused real-beam phase history to achieve better resolution than could be achieved by processing the real beam without it. Because the real aperture of the radar antenna is so small (compared to the wavelength in use), the radar energy spreads over a wide area (usually many degrees wide in a direction orthogonal (at right angles) to the direction of the platform (aircraft)). Doppler-beam sharpening takes advantage of the motion of the platform in that targets ahead of the platform return a Doppler upshifted signal (slightly higher in frequency) and targets behind the platform return a Doppler downshifted signal (slightly lower in frequency).

The amount of shift varies with the angle forward or backward from the ortho-normal direction. By knowing the speed of the platform, target signal return is placed in a specific angle "bin" that changes over time. Signals are integrated over time and thus the radar "beam" is synthetically reduced to a much smaller aperture – or more accurately (and based on the ability to distinguish smaller Doppler shifts) the system can have hundreds of very "tight" beams concurrently. This technique dramatically improves angular resolution; however, it is far more difficult to take advantage of this technique for range resolution. (See pulse-doppler radar).

Chirped (pulse-compressed) radars
A common technique for many radar systems (usually also found in SAR systems) is to "chirp" the signal. In a "chirped" radar, the pulse is allowed to be much longer. A longer pulse allows more energy to be emitted, and hence received, but usually hinders range resolution. But in a chirped radar, this longer pulse also has a frequency shift during the pulse (hence the chirp or frequency shift). When the "chirped" signal is returned, it must be correlated with the sent pulse. Classically, in analog systems, it is passed to a dispersive delay line (often a surface acoustic wave device) that has the property of varying velocity of propagation based on frequency. This technique "compresses" the pulse in time – thus having the effect of a much shorter pulse (improved range resolution) while having the benefit of longer pulse length (much more signal returned). Newer systems use digital pulse correlation to find the pulse return in the signal.

Data collection
In a typical SAR application, a single radar antenna is attached to an aircraft or spacecraft such that a substantial component of the antenna's radiated beam has a wave-propagation direction perpendicular to the flight-path direction. The beam is allowed to be broad in the vertical direction so it will illuminate the terrain from nearly beneath the aircraft out toward the horizon.

Image resolution and bandwidth
Resolution in the range dimension of the image is accomplished by creating pulses which define very short time intervals, either by emitting short pulses consisting of a carrier frequency and the necessary sidebands, all within a certain bandwidth, or by using longer "chirp pulses" in which frequency varies (often linearly) with time within that bandwidth. The differing times at which echoes return allow points at different distances to be distinguished.

Image resolution of SAR in its range coordinate (expressed in image pixels per distance unit) is mainly proportional to the radio bandwidth of whatever type of pulse is used. In the cross-range coordinate, the similar resolution is mainly proportional to the bandwidth of the Doppler shift of the signal returns within the beamwidth. Since Doppler frequency depends on the angle of the scattering point's direction from the broadside direction, the Doppler bandwidth available within the beamwidth is the same at all ranges. Hence the theoretical spatial resolution limits in both image dimensions remain constant with variation of range. However, in practice, both the errors that accumulate with data-collection time and the particular techniques used in post-processing further limit cross-range resolution at long ranges.

Image resolution and beamwidth

The total signal is that from a beamwidth-sized patch of the ground. To produce a beam that is narrow in the cross-range direction, diffraction effects require that the antenna be wide in that dimension. Therefore, the distinguishing, from each other, of co-range points simply by strengths of returns that persist for as long as they are within the beam width is difficult with aircraft-carryable antennas, because their beams can have linear widths only about two orders of magnitude (hundreds of times) smaller than the range. (Spacecraft-carryable ones can do 10 or more times better.) However, if both the amplitude and the phase of returns are recorded, then the portion of that multi-target return that was scattered radially from any smaller scene element can be extracted by phase-vector correlation of the total return with the form of the return expected from each such element.

The process can be thought of as combining the series of spatially distributed observations as if all had been made simultaneously with an antenna as long as the beamwidth and focused on that particular point. The "synthetic aperture" simulated at maximum system range by this process not only is longer than the real antenna, but, in practical applications, it is much longer than the radar aircraft, and tremendously longer than the radar spacecraft.

Although some references to SARs have characterized them as "radar telescopes", their actual optical analogy is the microscope, the detail in their images being smaller than the length of the synthetic aperture. In radar-engineering terms, while the target area is in the "far field" of the illuminating antenna, it is in the "near field" of the simulated one. Careful design and operation can accomplish resolution of items smaller than a millionth of the range, for example, 30 cm at 300 km, or about one foot at nearly 200 mi.

Pulse transmission and reception
The conversion of return delay time to geometric range can be very accurate because of the natural constancy of the speed and direction of propagation of electromagnetic waves. However, for an aircraft flying through the never-uniform and never-quiescent atmosphere, the relating of pulse transmission and reception times to successive geometric positions of the antenna must be accompanied by constant adjusting of the return phases to account for sensed irregularities in the flight path. SAR's in spacecraft avoid that atmosphere problem, but still must make corrections for known antenna movements due to rotations of the spacecraft, even those that are reactions to movements of onboard machinery. Locating a SAR in a crewed space vehicle may require that the humans carefully remain motionless relative to the vehicle during data collection periods.

Returns from scatterers within the range extent of any image are spread over a matching time interval. The inter-pulse period must be long enough to allow farthest-range returns from any pulse to finish arriving before the nearest-range ones from the next pulse begin to appear, so that those do not overlap each other in time. On the other hand, the interpulse rate must be fast enough to provide sufficient samples for the desired across-range (or across-beam) resolution. When the radar is to be carried by a high-speed vehicle and is to image a large area at fine resolution, those conditions may clash, leading to what has been called SAR's ambiguity problem. The same considerations apply to "conventional" radars also, but this problem occurs significantly only when resolution is so fine as to be available only through SAR processes. Since the basis of the problem is the information-carrying capacity of the single signal-input channel provided by one antenna, the only solution is to use additional channels fed by additional antennas. The system then becomes a hybrid of a SAR and a phased array, sometimes being called a Vernier array.

Data processing
Combining the series of observations requires significant computational resources, usually using Fourier transform techniques. The high digital computing speed now available allows such processing to be done in near-real time on board a SAR aircraft. (There is necessarily a minimum time delay until all parts of the signal have been received.) The result is a map of radar reflectivity, including both amplitude and phase.

Amplitude data
The amplitude information, when shown in a map-like display, gives information about ground cover in much the same way that a black-and-white photo does. Variations in processing may also be done in either vehicle-borne stations or ground stations for various purposes, so as to accentuate certain image features for detailed target-area analysis.

Phase data
Although the phase information in an image is generally not made available to a human observer of an image display device, it can be preserved numerically, and sometimes allows certain additional features of targets to be recognized.

Coherence speckle
Unfortunately, the phase differences between adjacent image picture elements ("pixels") also produce random interference effects called "coherence speckle", which is a sort of graininess with dimensions on the order of the resolution, causing the concept of resolution to take on a subtly different meaning. This effect is the same as is apparent both visually and photographically in laser-illuminated optical scenes. The scale of that random speckle structure is governed by the size of the synthetic aperture in wavelengths, and cannot be finer than the system's resolution. Speckle structure can be subdued at the expense of resolution.

Optical holography
Before rapid digital computers were available, the data processing was done using an optical holography technique. The analog radar data were recorded as a holographic interference pattern on photographic film at a scale permitting the film to preserve the signal bandwidths (for example, 1:1,000,000 for a radar using a 0.6-meter wavelength). Then light using, for example, 0.6-micrometer waves (as from a helium–neon laser) passing through the hologram could project a terrain image at a scale recordable on another film at reasonable processor focal distances of around a meter. This worked because both SAR and phased arrays are fundamentally similar to optical holography, but using microwaves instead of light waves. The "optical data-processors" developed for this radar purpose were the first effective analog optical computer systems, and were, in fact, devised before the holographic technique was fully adapted to optical imaging. Because of the different sources of range and across-range signal structures in the radar signals, optical data-processors for SAR included not only both spherical and cylindrical lenses, but sometimes conical ones.

Image appearance
The following considerations apply also to real-aperture terrain-imaging radars, but are more consequential when resolution in range is matched to a cross-beam resolution that is available only from a SAR.

Range, cross-range, and angles
The two dimensions of a radar image are range and cross-range. Radar images of limited patches of terrain can resemble oblique photographs, but not ones taken from the location of the radar. This is because the range coordinate in a radar image is perpendicular to the vertical-angle coordinate of an oblique photo. The apparent entrance-pupil position (or camera center) for viewing such an image is therefore not as if at the radar, but as if at a point from which the viewer's line of sight is perpendicular to the slant-range direction connecting radar and target, with slant-range increasing from top to bottom of the image.

Because slant ranges to level terrain vary in vertical angle, each elevation of such terrain appears as a curved surface, specifically a hyperbolic cosine one. Verticals at various ranges are perpendiculars to those curves. The viewer's apparent looking directions are parallel to the curve's "hypcos" axis. Items directly beneath the radar appear as if optically viewed horizontally (i.e., from the side) and those at far ranges as if optically viewed from directly above. These curvatures are not evident unless large extents of near-range terrain, including steep slant ranges, are being viewed.

Visibility
When viewed as specified above, fine-resolution radar images of small areas can appear most nearly like familiar optical ones, for two reasons. The first reason is easily understood by imagining a flagpole in the scene. The slant-range to its upper end is less than that to its base. Therefore, the pole can appear correctly top-end up only when viewed in the above orientation. Secondly, the radar illumination then being downward, shadows are seen in their most-familiar "overhead-lighting" direction.

The image of the pole's top will overlay that of some terrain point which is on the same slant range arc but at a shorter horizontal range ("ground-range"). Images of scene surfaces which faced both the illumination and the apparent eyepoint will have geometries that resemble those of an optical scene viewed from that eyepoint. However, slopes facing the radar will be foreshortened and ones facing away from it will be lengthened from their horizontal (map) dimensions. The former will therefore be brightened and the latter dimmed.

Returns from slopes steeper than perpendicular to slant range will be overlaid on those of lower-elevation terrain at a nearer ground-range, both being visible but intermingled. This is especially the case for vertical surfaces like the walls of buildings. Another viewing inconvenience that arises when a surface is steeper than perpendicular to the slant range is that it is then illuminated on one face but "viewed" from the reverse face. Then one "sees", for example, the radar-facing wall of a building as if from the inside, while the building's interior and the rear wall (that nearest to, hence expected to be optically visible to, the viewer) have vanished, since they lack illumination, being in the shadow of the front wall and the roof. Some return from the roof may overlay that from the front wall, and both of those may overlay return from terrain in front of the building. The visible building shadow will include those of all illuminated items. Long shadows may exhibit blurred edges due to the illuminating antenna's movement during the "time exposure" needed to create the image.

Mirroring artefacts and shadows
Surfaces that we usually consider rough will, if that roughness consists of relief less than the radar wavelength, behave as smooth mirrors, showing, beyond such a surface, additional images of items in front of it. Those mirror images will appear within the shadow of the mirroring surface, sometimes filling the entire shadow, thus preventing recognition of the shadow.

The direction of overlay of any scene point is not directly toward the radar, but toward that point of the SAR's current path direction that is nearest to the target point. If the SAR is "squinting" forward or aft away from the exactly broadside direction, then the illumination direction, and hence the shadow direction, will not be opposite to the overlay direction, but slanted to right or left from it. An image will appear with the correct projection geometry when viewed so that the overlay direction is vertical, the SAR's flight-path is above the image, and range increases somewhat downward.

Objects in motion
Objects in motion within a SAR scene alter the Doppler frequencies of the returns. Such objects therefore appear in the image at locations offset in the across-range direction by amounts proportional to the range-direction component of their velocity. Road vehicles may be depicted off the roadway and therefore not recognized as road traffic items. Trains appearing away from their tracks are more easily properly recognized by their length parallel to known trackage as well as by the absence of an equal length of railbed signature and of some adjacent terrain, both having been shadowed by the train. While images of moving vessels can be offset from the line of the earlier parts of their wakes, the more recent parts of the wake, which still partake of some of the vessel's motion, appear as curves connecting the vessel image to the relatively quiescent far-aft wake. In such identifiable cases, speed and direction of the moving items can be determined from the amounts of their offsets. The along-track component of a target's motion causes some defocus. Random motions such as that of wind-driven tree foliage, vehicles driven over rough terrain, or humans or other animals walking or running generally render those items not focusable, resulting in blurring or even effective invisibility.

These considerations, along with the speckle structure due to coherence, take some getting used to in order to correctly interpret SAR images. To assist in that, large collections of significant target signatures have been accumulated by performing many test flights over known terrains and cultural objects.

Relationship to phased arrays
A technique closely related to SAR uses an array (referred to as a "phased array") of real antenna elements spatially distributed over either one or two dimensions perpendicular to the radar-range dimension. These physical arrays are truly synthetic ones, indeed being created by synthesis of a collection of subsidiary physical antennas. Their operation need not involve motion relative to targets. All elements of these arrays receive simultaneously in real time, and the signals passing through them can be individually subjected to controlled shifts of the phases of those signals. One result can be to respond most strongly to radiation received from a specific small scene area, focusing on that area to determine its contribution to the total signal received. The coherently detected set of signals received over the entire array aperture can be replicated in several data-processing channels and processed differently in each. The set of responses thus traced to different small scene areas can be displayed together as an image of the scene.

In comparison, a SAR's (commonly) single physical antenna element gathers signals at different positions at different times. When the radar is carried by an aircraft or an orbiting vehicle, those positions are functions of a single variable, distance along the vehicle's path, which is a single mathematical dimension (not necessarily the same as a linear geometric dimension). The signals are stored, thus becoming functions, no longer of time, but of recording locations along that dimension. When the stored signals are read out later and combined with specific phase shifts, the result is the same as if the recorded data had been gathered by an equally long and shaped phased array. What is thus synthesized is a set of signals equivalent to what could have been received simultaneously by such an actual large-aperture (in one dimension) phased array. The SAR simulates (rather than synthesizes) that long one-dimensional phased array. Although the term in the title of this article has thus been incorrectly derived, it is now firmly established by half a century of usage.

While operation of a phased array is readily understood as a completely geometric technique, the fact that a synthetic aperture system gathers its data as it (or its target) moves at some speed means that phases which varied with the distance traveled originally varied with time, hence constituted temporal frequencies. Temporal frequencies being the variables commonly used by radar engineers, their analyses of SAR systems are usually (and very productively) couched in such terms. In particular, the variation of phase during flight over the length of the synthetic aperture is seen as a sequence of Doppler shifts of the received frequency from that of the transmitted frequency. Once the received data have been recorded and thus have become timeless, the SAR data-processing situation is also understandable as a special type of phased array, treatable as a completely geometric process.

The core of both the SAR and the phased array techniques is that the distances that radar waves travel to and back from each scene element consist of some integer number of wavelengths plus some fraction of a "final" wavelength. Those fractions cause differences between the phases of the re-radiation received at various SAR or array positions. Coherent detection is needed to capture the signal phase information in addition to the signal amplitude information. That type of detection requires finding the differences between the phases of the received signals and the simultaneous phase of a well-preserved sample of the transmitted illumination.

title: Synthetic-aperture radar


text:
Wikipedia:Articles for deletion/Diagon lane

This page is an archive of the discussion surrounding the proposed deletion of the page entitled Diagon lane.

This page is kept as an historic record.

The result of the debate was deletion.

Advertising for Web site. Tregoweth
 * Delete, spam. Shouldn't you sign your VfD listings? --Stormie 04:37, May 10, 2004 (UTC)
 * Sorry! Was an accident, not intentional. Tregoweth 06:25, May 10, 2004 (UTC)
 * Delete. Advert for just one of many similarly named websites. Andrewa 06:43, 10 May 2004 (UTC)
 * Delete. One of many Harry Potter fan sites, does not seem to be notable. Andris 14:35, May 10, 2004 (UTC)
 * Delete. Alcarillo 18:36, 10 May 2004 (UTC)
 * Delete. Fan sites of any kind are not acceptable at Wikipedia.--Beelzebubs 17:46, 15 May 2004 (UTC)
 * Delete. EddEdmondson 13:40, 16 May 2004 (UTC)

This page is now preserved as an archive of the debate up to the point of deletion and is no longer 'live'. Subsequent comments on the issue, the deletion or on the new method of assessing voting, should be placed on other relevant 'live' pages. Please do not edit this page.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
IBB

IBB may refer to:

Internet

 * Indiana Business Bulletin, a business-news website
 * Internet Bug Bounty, a Bug bounty program for Internet-related software

Institutes

 * Institute of Bioinformatics and Biotechnology, a scientific research institute in Pune, India
 * Institute of Biochemistry and Biophysics, a research institute in Iran
 * Ibrahim Badamasi Babangida University, university in Nigeria

Cities

 * Ibb (Arabic: إب), a city in Yemen

People

 * Ibrahim Badamasi Babangida, former President of Nigeria

Other

 * Intentional base on balls, a ploy in baseball
 * International Broadcasting Bureau, technical support body for the Voice of America and other US government broadcasting services
 * Istanbul Metropolitan Municipality (İstanbul Büyükşehir Belediyesi), the governing body of Istanbul
 * International Brotherhood of Boilermakers, Iron Ship Builders, Blacksmiths, Forgers and Helpers, a US trade union

title: IBB


text:
Talk:Bábism

Untitled
Made a fairly minor edit, but didn't seem minor enough to call minor. In any case, the reason I did not log in was because I have forgotten my password, and although I'm being e-mailed a new one, it has yet to arrive, and I'm getting impatient. The recent edit was done by me.

Typography
I've been through to do a bit of tidying up, but I fear I may have messed up the representation of some names. I started off changing ` to ' before I noticed that they seem to have different uses. If anyone passes this way who knows about these things, can you check that things are OK? Noisy | Talk 19:49, Jan 14, 2005 (UTC)

Might it be worth mentioning that there are few Babis left today, it is seen largely as a stepping stone religion into the Bahai faith and Azalism? Tomhab 15:22, 27 Jan 2005 (UTC)

Why does this page use Bahá'í orthography for non-English words when the Bāb, although a part of the Bahá'í religion, is in some respects independent of Bahá'íism? I'd like to change the orthography to accepted international standards (using macrons over long vowels instead of an accent mark) but wanted to first verify whether there's a specific reason not to do so. Kitabparast 07:02, July 30, 2005 (UTC)

 * Errrm... How is the Bab best known? He is best known as a part of the Baha'i faith, and certainly thats how he's spelt most. Sure he's got no solid connection so don't actually say there is one in the article but his name is most recognisable in the Baha'i form. -- Tomhab 08:44, 30 July 2005 (UTC)
 * Oops just noticed what page this is (Babis, not Bab). As long as there is a reference to how they're known in the Baha'i format the first time they're used, I'll just shut up :) -- Tomhab 08:51, 30 July 2005 (UTC)

I thought the Baha'i standard was based on the most common international standard used by academics. It's not an attempt to make others conform to Baha'i ways of spelling, but it was a way for the Baha'is to conform to the most commonly used standard of transliteration. Anyway that was my understanding. If you have some reference that shows otherwise I'd like to see it, and then you can have a ball on this page and the Bab's page. Cunado19 16:40, 30 July 2005 (UTC)

 * Not sure - I think it depends. I think the western standard is to use the "Shoghi Effendi" typography (not just in Baha'i texts), but a lot of scholarly literature use Bāb. I can see it could be debated either way and am not too bothered. Perhaps one thing to take into account is that the a-acute (á) is more like how wikipedia uses its accents. For instance "Bahá'í" is not how it is spelt on www.bahai.org - its normally spelt "Bahá’ís" (although not exclusively). Confused about the difference? The inverted comma is different. ' and ’. Wikipeida use ' as other articles use it (and also ’ isn't on my keyboard). Is it incorrect? I've tried to keep it using the ' in webpages as it gets confusing, but its hard to see.

 * In my opinion, as long as no-one gets confused what's being talked about it doesn't matter too much. This can be avoided by using brackets of what its otherwise known by.

 * One has a choice - follow what other encyclopaedias and definitions use, Bábís, or what scholarly typography uses Bābīs (debatably the "more correct" spelling). I can't personally say which wikipedia policy prefers, but generally they have a policy of "whatever, just make it consistent in the article" with most things (British/American spelling etc). -- Tomhab 22:15, 30 July 2005 (UTC)

 * Good point, Tomhab. I'll leave it as it is and not loose any sleep. :-) You are correct: as long as people know what's being talked about, it shouldn't matter too much. I think I'll go and have a ball on pages really related to Islām. Kitabparast 22:32, July 30, 2005 (UTC)

Kitab-i-Iqan
Having read the Kitab-i-Iqan carefully, I am surprised to read in the article, "...though in the Kitáb-i-Íqán, one of the most important polemical works of the Bábísm, and now the Bahá'ís, composed in 1858-1859, ...he still implicitly recognized the supremacy of Subh-i Azal." In the Iqan, Baha'u'llah is generally understood to be proving the claim of the Bab and hinting of his own station. So where does the italicized interpretation come from? --Occamy 20:30, 9 Feb 2005 (UTC)

Misleading figures
First off - the figure 20,000 is, in my experience, the number given to all those, Babis and Baha'is who have been martyred since 1844. It is misleading to compare this with "conservative" figures that are only relevant between 1844 and 1850. Please let me know if I'm mistaken, but I'm pretty certain I'm not. -- Tomhab 22:57, 30 July 2005 (UTC)

Standard naming
Names.... Well, In one section, I see Mulla Muhammad Ali of Barfarush, Quddus, and Muhammad Quddus being used. I may have noted the same for Tahirih. Can we acknowledge a single naming scheme form all these people? I suggest starting a page Talk:Bábís/naming with all the names used in wikipedia - no other name can be used unless it explicitly links it with the standard name. Sound good? Obviously the same can go for Mirza Yahya Nuri/Subh-i-Azal/Azal etc etc etc. -- Tomhab 22:57, 30 July 2005 (UTC)

Support

 * 1) Support as stated above -- Tomhab 22:57, 30 July 2005 (UTC)
 * 2) Support as stated above -- Kitabparast 23:14, July 30, 2005 (UTC)
 * 3) Support as stated above -- Cunado19 13:14, 8 August 2005 (UTC)

Comments

 * to consider -- which of the following formats should we use. I've seen all of them used. Cunado19 13:14, 8 August 2005 (UTC)

 * Somebody of Barfarush
 * Somebody-i-Barfarushi
 * Somebody Barfarushi

 * Yes, I agree, but without knowing exactly whats the best one to use, I suggest we standardise on one for each person. -- Tomhab 16:13, 8 August 2005 (UTC)

Mirza Jani journal
Is there only one copy of the journal written by Hâjji Mirza Jâni Kashani? I presume we're talking about the version included in the Nuqtat al-Kaf? Did anyone here add that line or know anything about it? Last I heard the Nuqtat al-Kaf has been widely produced as part of EG Brown's notes -- Tomhab 20:04, 4 August 2005 (UTC)

Move
I suggest moving the title of this article, but I admit I'm not sure what would be the best. I think "Bábí movement" would be the best, or "Bábí Faith", but "Bábís" just isn't a good title. Cuñado  -  Talk  00:26, 16 March 2006 (UTC)
 * What about Babism -- Jeff3000 03:36, 16 March 2006 (UTC)
 * Agree with Jeff3000. MARussellPESE 03:39, 16 March 2006 (UTC)
 * This was orphaned, I agree and I'll move the title to Bábism. -- Cuñado  [[image:Bahaitemplatestar.png|20px]] -  Talk  18:56, 27 March 2006 (UTC)

Maceoin
Maceoin is hardly a secondary source. If he states that secondary sources indicate only a small number of Babis killed, then those sources should be quoted and not him. Also, he states that Baha'i sources agree with the lower number, which they don't. I removed some of his opinions. Cuñado  -  Talk  18:40, 27 March 2006 (UTC)
 * I think MacEoin's statements need to be in the article. He was an academic that did a lot of work on Babism and Shakiism and based on his academic work which he's published he's believes that there is around 2000 to 3000 Babis killed. He's done the research himself, looking over many many sources and has added up the numbers of people killed and come up with the number; it is not a number that is based on any other work but by his historical analyses (such as newspapers, etc).  This of course is lower than what Baha'is believe based on Abdu'l-Baha's statements (which Baha'is use and state that MacEoin's estimates are too low because they don't include the numerous persecutions that were not accounted for), but MacEoin's statement is an academic source, and should be in the article for NPOV. I will be reinserting it.-- Jeff3000 18:50, 27 March 2006 (UTC)

 * It should be clear what he was doing then. If someone tried to count how many blacks were lynched in the US over the last 4 centuries, and their sources were limited to reading newspaper articles, they would be a few hundred thousand off. Cuñado  [[image:Bahaitemplatestar.png|20px]] -  Talk  19:00, 27 March 2006 (UTC)

 * I agree with both of y'all's sentiments here. MacEoin's assertion is quite valid but should have a specific citation though. Can you pick that up, Jeff? Cuñado's got a quite valid point. The Iranian hinterland was a very, very, bloody place to be at the time. Much less flashy that Ft. Shaykh Tabarsi, but a lot easier to get dragged out of your house. The comparison to lynching is apt. And there were precious few outsiders who kept anything remotely like records. The Baha'i numbers are probably inflated with double counts and such, but I'll bet they are better than anything that anybody else has — and much better than MacEoin's. The Baha'i numbers are exaggerated by an order of magnitude? I doubt it. MARussellPESE 22:11, 27 March 2006 (UTC)

 * I know this is an old discussion, but I have a bit of experience with this. Unlike most contemporary Baha'i commentators who weigh on in the "numbers of martyrs" debate, MacEoin actually read all available original sources, in the original languages. When I was researching my master's thesis on Babi/Shii martyrdom I read all available English- and French-language ones and looked at, though couldn't fully read, some of the Arabic/Persian primary sources. My own research, while only a fraction of MacEoin's, confirmed MacEoin's numbers. It is also instructive to read how and why the numbers became inflated ten-fold, and these reasons are simple and obvious matters of hagiography and story-telling, reasons which the very pro-Baha'i David Piff affirms in his magnum opus Baha'i Lore. That is, MacEoin is not claiming any devious intent in Baha'i's inflating the numbers of martyrs, but rather it is a benign phenomenon in history and a community's self-definition. I am in no way defending MacEoin's later anti-Baha'i stance, but I can somewhat defend his statistics. Jonah Winters (talk) 15:43, 13 July 2010 (UTC)

I hadn't expected to return to this subject but does this tweak people's interest? "Very speedily the Mohammedan authorities became alarmed, especially after an unsuccessful attack upon the life of the Persian Shah by a crazed Babi, and persecution of the most terrible character was set on foot. In the frenzied massacres which followed, thirty thousand men, women and children were cut down in cold blood. Outrages of every description were practised, cruelties of the last degree of refinement perpetrated, upon defenseless and terrified populations. The leaders were seized, some of them killed and others imprisoned. Baha o'llah, the successor of the Bab, was stripped of his property, imprisoned in a noisome dungeon, and at last banished from the kingdom. In Turkey, where he took refuge, he was in 1868 doomed to the prison of Akka in Palestine, where he remained till his death. And here also, for a period of forty years, languished his disciple and later successor, Abdul Baha."

Smkolins (talk) 21:44, 19 July 2010 (UTC)

Lot of history but lacking doctrinal content
I understand that a page on a specific religion or sect should contain all the basic tenets of its doctrine. I find that this page, being about a movement and not about a person, contains a lot of biographical and historical data but very few, if any, explanations about the actual contents of Bábism as a distinct religious path. I suggest that the article needs to be reorganized and expanded in that area in order to improve it. --Jdemarcos 13:07, 11 July 2006 (UTC)
 * Good point. I don't have access to books (such as MacEoin's The sources for early Babi doctrine and history : a survey or Amanat's Resurection and Renewall) that would be verifiable sources.  Regardless, I'll try to find some on verifiable information on the web, and add some stuff. -- Jeff3000 00:21, 12 July 2006 (UTC)
 * Ok, I've added some beliefs. I've found some of Amanat's and MacEoin's essays on the web, in addition to Browne and Esslemeont, and used them as references. -- Jeff3000 03:43, 12 July 2006 (UTC)

Move to Babi Faith.
That's the title. Zazaban 23:59, 3 September 2006 (UTC)

 * I'm indifferent, but I would prefer Bábism, since it's the most common reference in academics (in my experience). Cuñado  [[image:Bahaitemplatestar.png|20px]] -  Talk  07:08, 4 September 2006 (UTC)
 * I think Babism is the most common usage, and should stay. -- Jeff3000 15:01, 4 September 2006 (UTC)

In the outside world I've heard "baha'ism" more than "Baha'i faith" but does that make it correct? People still use Czechoslovakia for heaven's sake!
 * In English, the "Baha'i Faith" is orders of magnitude more common than "Baha'ism", (in may not be that way in other languages) not to mention that "Baha'ism" is commonly used in a belittling way by attackers of the Baha'i Faith. On the other hand, Babism is much more common than Babi Faith. And note that even though the Czech government would like people to call what is most commonly known as the Czech Republic, Czechia, the article is still titled the Czech Republic since that is the most common usage. -- Jeff3000 18:16, 4 September 2006 (UTC)
 * Me again, weighing in on an old discussion. I can confirm, from my study of Arabic and linguistics in grad school, that "Babism" (no accent) would be more correct, because it's an English word, whereas "Bábí" is not. Think for example of the difference between the accented word "Qur'án", from Arabic, vs. the non-accented word "Quranic", from English. Jonah Winters (talk) 15:47, 13 July 2010 (UTC)

Badasht
The statement under the heading of Fort Tabarsi is incorrect I believe. The fort established at the shrine of Shaykh Tabarsi is on the northern slopes of the Alborz mountains. I have yet to find the exact location, but it is relatively close to Babúl (Barfarush), the home of Quddus, and Sari. The context in Nabil's narrative implies this. In fact the name "Tabarsi" implies an origin in Tabaristan, the old name for Mazindaran.

I do know where Badasht is located. I have it on a map, and it is just east of the current town of Emamrud. Go here: Multimap, select "Rest of the World" at the bottom of the pull-down, then type in "Iran" for country, and "Bedasht" for town. Make sure and spell it with an "e". This is where it should be according to the historical texts.

Now one interesting question I've always had is why they were walking west from Mashhad and ended up near Babul. Nobody seems to address where they were trying to go.

Another interesting point about the battle at Tabarsi is the prophetic/mystical nature of the event. The number of participants (313) is said in some untranslated texts to represent each of the previous Manifestations "endowed with constancy" (major prophets), while Quddus took on the role of the Báb (he wore the Báb's turban). Then Baha'u'llah makes an appearance as the next Manifestation. As I understand, the number of participants in the Battle of Badr was also 313, and Shi'i prophecy points to this being the number of the Mahdi's supporters.

In relation to Badasht, I made a note in the discussion for the Conference of Badasht that I plan on working on that article. -- Parsa 23:47, 11 December 2006 (UTC)

 * I read through much of the first chapter on the Mazindaran Upheaval in Nabil's narrative. I have a couple things to correct in the statement above. Mulla Husayn was supposed to be heading to Karbila from Mashhad. He was then told by the Báb to go in aid of Quddus, who was then imprisoned in Sari. The trip west actually took several months. The Babis ended up near Barfarush (Babul), where the first confrontation took place. Ultimately, the were escorted by a squad of 100 armed men out of Barfarush, and were to be taken as far as Shir-Gah. The leader took them down a forest road, and betrayed them by attacking the Babis. It was from there, part way to Shir-Gah, that the Babis took refuge in the shrine of Shaykh Tabarsi. The Guardian says it was 14 mile SE of Barfarush near a village called "Afra." This would have been near modern Qa'emshahr. There is an "Afra Takht" nearby, but it is east of Qa'emshahr. Shir-Gah lies south of Qa'emshahr on the road through the mountains to Tihran.

 * Mulla Husayn wore the Bab's turban, not Quddus, but Quddus did fill the role of the Mahdi since he fulfilled hadith prophesies related the Mahdi at Tabarsi.

 * The actual mystery was not where they were going from Mashhad, but rather why they were on the road to Shir-Gah. Mulla Husayn agreed to go to Amul after talks with leaders of Barfarush. Amul is west of Barfarush. However he ended up heading to Shir-Gah which is to the southeast. No explantion for this is given. See this comment. -- Parsa 08:50, 13 December 2006 (UTC)

Uprisings and Massacres section
I tend to disagree with the overall characterization of the struggles involving Babis as being "revolts." In once sense, the Revelation of the Bab was a revolution... That is in the spiritual sense. However, I think it's wrong to imply that the Babis were somehow continuously trying to cause revolt and insurrection. The view presented in Nabil, God Passes By, and other sources, is that the struggles were defensive actions. This is illustrated by the behavior of the Babis before and during the battle at the shrine of Shaykh Tabarsi. On nearing Barfarush, the mob incited by the chief religious leader, attacked the approaching Babis. Mulla Husayn ordered nobody to retaliate. It was not until they had been attacked three times that he charged into the mob and killed the last assailant. Once again, when the Babis were in the caravanserai at Barfarush, Mulla Husayn ordered the call to prayer. Three Babis in turn attemped the recitation of the adhan but were each killed. Only after the third death did Husayn order the gates to be opened and the mob attacked. I believe the overall wording and tone of the section needs to be altered to reflect this fact. -- Parsa 05:47, 14 December 2006 (UTC)
 * While I agree with you, there are academic viewpoints that disagree with your analysis, and the Baha'i viewpoints; main among them are Denis MacEoin's work. As I mentioned in the Talk:Baha'i Faith, articles must use a neutral point of view, and secondary works are preferred to primary reports such as the Dawnbreakers. -- Jeff3000 06:20, 14 December 2006 (UTC)

The Dawnbreakers is only a primary source when Zarandi recounts his own experiences. For the section on Shaykh Tabarsi, he is acting as an historian reporting the first hand accounts of others. In that case the work is a secondary source. God Passes By is also a secondary source, as is Resurrection and Renewal. So then it's a matter of choice, preference, etc. In the past, a great many encyclopedias used non-Baha'i sources in what can be presumed to be an attempt to be neutral. However, many of these sources were books by Iranian enemies of the faith or by western missionaries. Western reporters of the events in Mazindaran, Zanjan and Nayriz were getting their information from the government, not first hand (see Momen, "The Babi and Baha'i Religions, 1844-1944, Some Contemporary Western Accounts). If we agree to their characterizations of the events as revolts against the government, we may also have to agree to their views of the Babis as "fanatics". Should we ignore Christian authors of Christian history in favor of agnostic or Buddhist scholars writing on Christianity? Isn't a Buddhist, who grows up in that tradition to be trusted in his accounts of Budhhist history? Should we universally ignore all historical accounts of adherents of a faith in favor modern academic scholars? I doubt if this is the view of the folks writing articles for Wikipedia on Islamic history. Just because an account is from a Baha'i source does not mean it is non-factual. If it is factual, then it is neutral. -- Parsa 07:30, 14 December 2006 (UTC)
 * Sorry but it doesn't work that way. Unfortunately, optics are just as important as facts, and using only Baha'i sources does not provide the right optics, especially when there are qualified historians who are not polemic who give the opposite viewpoint.  Both viewpoints must be given, and qualified with "Baha'i sources state ..." and "Denis MacEoin says ...".  Look over the countless Christian and Jewish articles where there has been debates over how the religion sees itself and historians see it. -- Jeff3000 14:24, 14 December 2006 (UTC)

The problem I have is not concerned with presenting multiple sides, but rather with the general use of the term revolt. That seems to be non-neutral in the sense that it does indeed support the Shi'i contention that the Babis were political revolutionaries and seditionists. I don't want to water things down, but perhaps a more neutral terminology can be used such as the terms "upheaval", "struggle", "conflict", "confrontation", etc. I have no argument against presenting the opposing views as is done in the introductory statement to the section. Yes, present Baha'i, academic, Shi'i, governmental, or any other point of view as long as the source is identified and explained. -- Parsa 16:04, 14 December 2006 (UTC)

Bábism and Bábis
When the title of this article was changed to Bábism in March, the opening description was not changed to match. The first sentence does not define Bábism as the religion of the Báb, but begins by talking about Bábis. The opening should be similar to that on the Bahá'í Faith: "The Bahá'í Faith is a religion founded by Bahá'u'lláh in 19th century Persia. Bahá'ís number around 6 million in more than 200 countries around the world.[1][2]" Reference to the Báb should be in the first paragraph, and an explanation that adherents of the religion are called Bábis should follow later. -- Parsa 18:11, 14 December 2006 (UTC)

Title of this page
Hi guys, I am much impressed by this article - but I have to point out a few things as a Bahá'í - The correct way to describe the religion brought by The Báb is - The Bábi Faith. The correct way to describe the revelation of Baha'u'llah and the religion followed by over 7 millions Bahá'ís worldwide is The Bahá'í Faith - Not Babism, Not Bahaism - that is just plain wrong and it's really annoying when others add the -ism on the end! As Bahá'i we believe in The Báb as a Messenger of God in His own right as well as the forerunner of Bahá'u'lláh - The Báb is a major part of Bahá'i history!! Is Christianity called Christanism or Islam called Islamism? I feel aggrieved by this, even though it is in reality just a word - but because I feel its a way people use to put down an expression of Faith they either don't understand, have not adequaltely researched or simply oppose. Please get it right! Yours, Fleur Fleurba 23:38, 23 September 2007 (UTC)
 * Fleurba, some of the main policies of Wikipedia is neutral point of view, verifiability and no original research. As part of these policies, Wikipedia uses terms that are used in the majority of reliable sources, and not what we believe as individuals or spokesmen.  The reliable sources are usually secondary sources that have published in mediums which have editorial oversight.  For the religion of the Bab, most sources call it Babism, and the Wikipedia Manual of style on titles means that the most used term has to be used.  Thus the term has to stay.  As for the Baha'i Faith versus Bahaism the term Baha'i Faith is used much more that Baha'ism and that is why the title of that article is Baha'i Faith.  Regards, -- Jeff3000 00:34, 24 September 2007 (UTC)

Translation of Bab
the word Bab simply means "door", not gate. Bawwabah is the Arabic word for gate. (67.171.224.169 (talk) 00:36, 16 May 2008 (UTC))
 * The Encyclopedia Iranica article on the Bab states that it is translated gate, not door. Regards, -- Jeff3000 (talk) 04:40, 16 May 2008 (UTC)

Request for Comment - Bahá'í/Bábí split
There's a proposal on Talk:Bahá'í/Bábí split to rename that article and your views are requested on that page. Thanks! AndrewRT(Talk) 20:29, 25 January 2009 (UTC)

Numbers of babists?
Are there still any followers of babism? the article does not make that clear I'd like to know! If you have figures plz provide them. —Preceding unsigned comment added by 140.230.23.155 (talk) 11:35, 12 November 2009 (UTC)
 * The Babis either followed Baha'u'llah and became Baha'is, or supported Subh-i-Azal, and were thus then known as Azalis. In the "Succession" section it notes that there is probably no more than 1000 Azalis at this point.  Regards, -- Jeff3000 (talk) 14:15, 12 November 2009 (UTC)

of Uprisings and Massacres section and Maceoin input
The primary available reference appears to be
 * though I'm missing some of the details of the ref (issn, doi of Religion journal??)

There seems to be a
 * though I've also seen it referenced as
 * but I've not see the actual article(s) available anywhere. Smkolins (talk) 04:06, 19 January 2010 (UTC)

Perhaps to be added
"A number of Babis appear to have traveled to Karbalāʾ with this hope and, following instructions in the Qayyūm al-asmāʾ, to have purchased arms in readiness for the jehād that would follow the Bāb’s appearance and the advent of the imam. In the end, the Bāb failed to reach Karbalāʾ as promised, returning instead to Shiraz via Būšehr in the summer of 1261/1845. His arrest en route to his home town by agents of the governor of Shiraz considerably restricted his freedom of action and prevented even a late arrival in Iraq. As a result, a number of the newly-converted abandoned their allegiance, leaving only a small core of believers, who were forced to begin the work of proselytization once more (al-Qatīl b. al-Karbalāʾī, letter in Māzandarānī, Ẓohūr al-ḥaqq III, p. 503)."--Kazemita1 (talk) 17:40, 12 November 2013 (UTC)

Manifestion of God
As for Manifestion there are many manifestions in the same time, the the greater atribute of God is presented in Shia most authentic Hadith Book al Kafi as the 14 Imams specialy the five in other books for that the Bayani Azali claim about that there is only one manifestion of god is false Bab has claimed himself as the return of the 12th Imam al Hujjah (The proof) in Persian Bayan the Proof returned as The point of Bayan (Bab) which is the same as the point of Furqan (Imam Mahdi) the first two to believe in the call of Qaim are Muhammad and Ali so Muhammad has manifested as Bushr'ui the first to believe and Ali as the second to believe, the Hadith books also say that Imam Hussein will return after Imam Mahdi and Hussein will put The 12th Imam in the grave after his death and will build his shrine and in Shia Hadith there is a comprision between Imam Hussein and Jesus the Christ both were sons of two Ladies of worlds both were the sons of virgins and both were born by 6 months and for Krishna He is Buddha himself and Krishna in some Non Hindu (But Jain) sources died thirsty just like Imam Hussein so for that Bahaullah is the return of these figures in the Babism who has fullfilled their prophecy and his manifestion was greater than of Bab according to Bahais because He was one return of one of Ahlul Kisa' but His role in Islamic Prophecies was just similar to John the baptist for Jews and Bab's role was the one who has peacefuly fullfilled the Islamic Prophecies like Jesus for Jews but Bab's role in the new religion was similar to John the baptist and Bahaullah's role was similar to Jesus the Christ. 94.252.145.1 (talk) 08:58, 6 April 2024 (UTC)

title: Talk:Bábism


text:
Dinosaur National Monument

Dinosaur National Monument is an American national monument located on the southeast flank of the Uinta Mountains on the border between Colorado and Utah at the confluence of the Green and Yampa rivers. Although most of the monument area is in Moffat County, Colorado, the Dinosaur Quarry is located in Utah, north of the town of Jensen, Utah. The nearest Colorado town is Dinosaur while the nearest city is Vernal, Utah.

Originally preserved in 1915 to protect its famous Dinosaur Quarry, the monument was greatly expanded in 1938 to include its wealth of natural history. The park's wild landscapes, topography, geology, paleontology, and history make it a unique resource for both science and recreation. The park contains over 800 paleontological sites and has fossils of dinosaurs including Allosaurus, Deinonychus, Abydosaurus, and various sauropods. The Abydosaurus consists of a nearly complete skull, the lower jaw, and first four neck vertebrae. The specimen was found at the base of the Mussentuchit Member of the Cedar Mountain Formation and is the holotype for the description.

Paleontologist Earl Douglass of the Carnegie Museum discovered eight vertebra of an Apatosaurus on August 17, 1909, which became the first dinosaur skeleton discovered and excavated at the new Carnegie Quarry. The area around the quarry was declared a national monument on October 4, 1915. The International Dark-Sky Association designated Dinosaur National Monument an International Dark Sky Park in April 2019.

Geology
The rock layer enclosing the fossils is a sandstone and conglomerate bed of alluvial or river bed origin known as the Morrison Formation from the Jurassic Period some 150 million years old. The dinosaurs and other ancient animals were carried by the river system which eventually entombed their remains in Utah.

The pile of sediments were later buried and lithified into solid rock. The layers of rock were later uplifted and tilted to their present angle by the mountain building forces that formed the Uinta Mountains during the Laramide orogeny. The relentless forces of erosion exposed the layers at the surface to be found by paleontologists.

Fremont people
The Fremont people lived in the area of what is now Dinosaur National Monument before the 14th century, with archaeological evidence dating from c. 200 to c.  1300. Archaeologists first studied and named the Fremont culture along the Fremont River in south-central Utah and have since traced it through much of the Green and Colorado River drainages.

The Fremont did not build large permanent dwellings; instead, they lived in small bands within natural shelters, such as rock overhangs or shallow caves, or small villages. They consumed plant foods, such as pine nuts, berries, and cactus fruits, as well as wild game, including mule deer, bighorn sheep, smaller mammals, and birds. They also grew corn, beans, and squash, sometimes using irrigation techniques.

The fate of the Fremont culture is unclear. Recent theories suggest that the Fremont's lifestyle may have changed due to drought or other climate factors, dwindling natural resources, or the influence of other neighboring cultures. They left evidence of their presence in the form of petroglyphs and pictographs of human and animal figures, and abstract designs. Human figures typically have trapezoidal bodies and elaborate decorations that suggest headdresses, earrings, necklaces, or shields. The animal figures include bighorn sheep, birds, snakes, and lizards. Purely abstract or geometric designs, such as circles, spirals, and various combinations of lines, are common. Many designs in the monument are accessible for close viewing, along four trails in Utah, one of which is near the visitor center, and a fifth trail in Colorado.

Early scientific explorations
The dinosaur fossil beds (bone beds) were discovered in 1909 by Earl Douglass, a paleontologist working and collecting for the Carnegie Museum of Natural History. He and his crews excavated thousands of fossils and shipped them back to the museum in Pittsburgh, Pennsylvania for study and display.

National monument
President Woodrow Wilson proclaimed the dinosaur beds as Dinosaur National Monument in 1915. The monument boundaries were expanded in 1938 from the original 80 acre surrounding the dinosaur quarry in Utah, to 210844 acre in Utah and Colorado, encompassing the river canyons of the Green and Yampa.

Echo Park Dam controversy
The plans made by the U.S. Bureau of Reclamation on a ten-dam, billion dollar Colorado River Storage Project began to arouse opposition in the early 1950s when it was announced that one of the proposed dams would be at Echo Park, in the middle of Dinosaur National Monument. The controversy assumed major proportions, dominating conservation politics for years. David Brower, executive director of the Sierra Club, and Howard Zahniser of The Wilderness Society led an unprecedented nationwide campaign to preserve the free-flowing rivers and scenic canyons of the Green and Yampa Rivers. They argued that if a national monument was not safe from development, how could any wildland be kept intact?

On the other side of the argument were powerful members of Congress from western states, who were committed to the project in order to secure water rights, obtain cheap hydroelectric power and develop reservoirs as tourist destinations. After much debate, Congress settled on a compromise that eliminated Echo Park Dam and authorized the rest of the project. The Colorado River Storage Project Act became law on April 11, 1956. It stated, "that no dam or reservoir constructed under the authorization of the Act shall be within any National Park or Monument."

Historic places
Places on the list of National Register of Historic Places include:
 * Prehistoric sites
 * Castle Park Archeological District, a prehistoric residential site with inhabition during 1500 - 1000 BC and again from AD 1000 - 1899 by the Prehistoric Fremont culture, Ute and Shoshone people.
 * Mantle's Cave is a prehistoric Fremont culture residential site from 499 BC - AD 1749.
 * Other sites
 * Josie Bassett Morris Ranch Complex
 * Denis Julien Inscription
 * Rial Chew Ranch Complex
 * Upper Wade and Curtis Cabin

Climate
The Dinosaur National Monument sits on a vast area of desert land in Northwestern Colorado and Northeastern Utah. Typical of high deserts, summer temperatures can be exceedingly hot, while winter temperatures can be very cold. Snowfall is common, but the snow melts rapidly in the arid and sunny climates of these states. Rainfall is very low, and the evaporation rate classifies the area as desert, even though the rainfall exceeds 10 inches.

The quarry
The "Wall of Bones" located within the Dinosaur Quarry building in the park consists of a steeply tilted (67° from horizontal) rock layer which contains thousands of dinosaur fossils. The preserved section is only a portion of what was originally present when Douglass made his discovery as seen on the map above. When work ceased in 1922, a portion of the quarry was left for future development. This work began as part of President Franklin Roosevelt's Civil Works Administration, which provided employment during the Depression under the Transient Relief Service and later under the Works Progress Administration. This work included constructing a road to the quarry, removal of overburden covering the bone-bearing strata, and building of a small, temporary museum. World War II interrupted work, but this was resumed in 1951 with the building of a small metal building over the east portion of the quarry to test whether bone was abundant enough to warrant a larger, more permanent building. This more permanent building was erected in the mid-1950s as part of the National Park Service Mission 66 plan. The architectural design was high controversial for its ultra-modern use of glass, steel and concrete ramp that spiraled around a cylindrical office tower. The building opened at the dedication ceremony on June 1, 1958. The design had two levels and abundant natural light so that visitors could watch technicians remove the hard rock to reveal the excavated fossil bones in-situ.

In July 2006, the Quarry Visitor Center was closed due to structural problems that since 1958 had plagued the building because it was built on unstable clay. The decision was made to build a new facility elsewhere in the monument to house the visitor center and administrative functions, making it easier to resolve the structural problems of the quarry building while still retaining a portion of the historic Mission 66 era exhibit hall. It was announced in April 2009 that Dinosaur National Monument would receive $13.1 million to refurbish and reopen the gallery as part of the Obama administration's $750 billion stimulus plan. The Park Service successfully rebuilt the Quarry Exhibit Hall, supporting its weight on 70-foot steel micropile columns that extend to the bedrock below the unstable clay. The Dinosaur Quarry was reopened in Fall 2011.

Fossils from Carnegie Quarry

 * Now enclosed by the Dinosaur Quarry building (Gilmore (1936), Foster (2003); Good (2004).

 * Planta
 * Coniferophyta

 * Mollusca
 * Unio sp.
 * Vetulonia sp.

 * Reptilia
 * Testudines
 * Amphichelydia
 * Glyptops plicatus
 * Dinochelys whitei
 * Rhynchocephalia
 * Opisthias rarus
 * Crocodilia
 * Mesosuchia
 * Gonipholididae
 * Goniopholis sp.
 * Atoposauridae
 * Hoplosuchus kayi (h)

 * Dinosauria
 * Saurischia
 * Theropoda
 * Ceratosaurus sp.
 * Torvosaurus sp.
 * Allosaurus fragilis
 * Sauropoda
 * Apatosaurus louisae (h)
 * Barosaurus lentus
 * Camarasaurus lentus
 * Diplodocus hallorum
 * Uintasaurus douglassi (h) (now Camarasaurus lentus)
 * Ornithischia
 * Stegosauria
 * Stegosaurus ungulatus
 * Ornithopoda
 * Iguanodontia
 * Camptosaurus aphanoecetes (h)
 * Dryosauridae
 * Dryosaurus elderae (h)

 * (h) = holotype

title: Dinosaur National Monument