Is Map Generalisation a Computational Cartography Problem?

Guillaume Touya LASTIG, Univ Gustave Eiffel, IGN-ENSG, F-77420 Champs-sur-Marne, France Map generalisation is one of the processes of map design, when the spatial data used to make the map is too detailed for the scale of the map. Map generalisation seeks to abstract and simplify this detailed spatial information to represent it on the map with a good legibility. Map generalisation involves different types of transformations: selection, simplification, displacement, aggregation, collapse, etc. Historically, computational geometry researchers greatly contributed to the automation of map generalisation by proposing algorithms to achieve some of these atomic transformations. But the research questions addressed by researchers on map generalisation have changed over the years, with the progress on the automation, and the changes in the way people use maps (apparition of multi-scale zoomable web maps). Is map generalisation still a computational cartography problem?

To discuss this rhetorical question, this presentation illustrates the current issues of map generalisation, with past contribution of computational cartography and possible computational cartography problems. For instance, there are still needs for new specific algorithms, either because maps are much more diverse, or because the larger scale range calls for new transformations. As maps tend to mix elements of topographic maps and elements of schematized maps, computational cartography is also relevant to solve this task.

Finally, as the current trend in map generalisation is the use of deep learning models, the presentation discusses the relevance of computational cartography techniques in this context.

The slides of the talk are available online: https://fr.slideshare.net/MapMuxing/invitedtalkcompcartotouyapdf


Guillaume Touya

Jean-Marie Favreau

Jérémy Kalsron

Schematizing Crossroads from Abstract Textual Descriptions

May 24, 2022

The use of cartographic representations among people with visual impairments (PVI) is often limited by the lack of available materials. However, two uses have been identified: diagrams made with sticks magnetised to a metal plate (Figure 1) are used by Orientation and Mobility instructors as a discussion aid around complex areas (typically intersections), and more accurate maps made by transcribing adapters are sometimes produced for regular use. While classical variations of the generalisation and stylisation approaches allow for the production of fairly accurate maps [START_REF] Jiang | Mapping road crossings for visually impaired people[END_REF], for example from OpenStreetMap data (figure 2), there are currently no known approaches to producing a more schematic representation, in the manner of the locomotion instructors' magnets.

Mackaness and Reimer define schematized maps as "bereft of detail, emphasising properties such as causality, connectivity, and flow", where abstraction is more important than the correct geographical location [START_REF] Mackaness | Generalisation in the Context of Schematised Maps[END_REF]. Hence, a schematized map seems to be a good way to graphically represent crossroads to PVI: the map should be easy to read by fingers; it should focus on footways (sidewalks, crossings), and identify the dangerous space dedicated to cars with a specific texture.

In order to produce a synthetic map satisfying these objectives, we propose to describe sidewalks by lines, traffic islands by discs, zebra crossings by simple pictograms, and to fill in the road with an easily identifiable texture (Figure 3), taking care to keep a white space between the objects to facilitate their tactile reading.

The production of a schematic representation of a crossroad we propose is based on the representation of the crossroad in an abstract representation model, integrating the different functional elements of a crossroad: branches, lanes, pavements, pedestrian crossings [START_REF] Kalsron | Le carrefour dont vous êtes le héros[END_REF]. This abstract model is dedicated to generate a textual/sound description that accompanies the tactile map.

We therefore propose to reconstruct a simplified geometric instance for each element of this abstract representation. A simplified geometric instance of sidewalks (using straight lines along each branch) is registered on the OpenStreetMap data to match the global shape of the crossroad (step 1). A regularization step is then applied to the sidewalk lines to obtain orientations proportional to π/4, in a similar process to metro map schematization [NW11] (step 2); circular pictograms and zebra pictograms are located at the adjusted location of the traffic islands and crossings (step 3); the road area is reconstructed from the sidewalk lines, and filled with a recognizable texture (step 4); blank spaces are generated using an offset algorithm from sidewalk lines and pictograms (step 5).

We plan to implement these algorithms in the next months and test with PVI if the schematized map is more usable than the accurate tactile maps.

Figure 1 :

 1 Figure 1: Three examples of maps made with magnets

Figure 2 :

 2 Figure 2: A 2D view of a tactile map (copyright Yuhao Markie Jiang), and the corresponding intersection in OpenStreetMap.

Figure 3 :

 3 Figure 3: A manually generated schematised map of the crossroad from Figure 2, based on the textual description and conflated with the geographic data.

Acknowledgements

This research is part of the ACTIVmap project that was funded by ANR (Agence Nationale de la Recherche) ANR-19-CE19-0005.


Olivier Pourret

Christopher Jackson

Evan B Goldstein

Samantha Teplitzky

Jess Hillman

Modern geoscience publishing

Viewpoint: Modern geoscience publishing

Olivier Pourret and the EarthArXiv Team contend that preprints can help bring the geosciences into the 21 st century.

A preprint is the initial version of a research article, often (but not always) before submission to a journal and thus before formal peer-review. Preprints help modernise geoscience by removing structural barriers that inhibit broad participation in the scientific process, and which are slowing progress towards a more open and transparent research culture.

Preprints are not new; they have been around since the 1960s. In August 1991, a centralized web network, arXiv (https://arxiv.org/, pronounced "är kīv", from the Greek letter "chi"), was established to share physics preprints. arXiv has supported the fields of physics, mathematics and computer science for over 30 years, during which time the pace of dissemination of scientific information has quickened. In recent years, more disciplinesincluding the geosciences, via EarthArXiv (www.eartharxiv.org/; [START_REF] Narock | Earth science is ready for preprints[END_REF] and ESSOAr (www.essoar.org)have started to take advantage of preprints.

Preprints have many well-documented benefits for both researchers and the public (e.g., [START_REF] Bourne | Ten simple rules to consider regarding preprint submission[END_REF][START_REF] Sarabipour | On the value of preprints: An early career researcher perspective[END_REF][START_REF] Pourret | On the Potential of Preprints in Geochemistry: The Good, the Bad, and the Ugly[END_REF]. For example, preprints enable:

During the COVID-19 pandemic, the medical and broader scientific community, as well as the public, have seen the role for preprints in opening and accelerating the scientific process for the benefit of humanity [START_REF] Besançon | Open science saves lives: lessons from the COVID-19 pandemic[END_REF]. Preprints are now an established part of the scientific publication and communication process, and are here to stay [START_REF] Lanati | Research Funding Bodies Need to Follow Scientific Evidence: Preprints Are Here to Stay[END_REF].

Preprints are helping to modernise the geosciences by removing structural barriers that make science and knowledge less accessible to those who often fund knowledge-creationtaxpayersas well as making research results quickly available to all who might benefit from it.

Olivier Pourret, Christopher Jackson, Samantha Teplitzky, Evan Goldstein, Jess Hillman, and the EarthArXiv team.

• Rapid sharing of research results, which can be critical for time-sensitive studies (such as after disasters), as well as for early career researchers applying for jobs, or any academic applying for grants or a promotion, given that journal-led peer review can take many months to years; • Greater visibility and accessibility for research outputs, given there is no charge for posting or reading a preprint, especially for those who do not have access to paywalled journals, or limited access due to remote working (such as during lockdowns); • Additional peer feedback beyond that provided by journal-led peer review, enhancing the possibility of collaboration via community input and discussion; • Researchers to establish priority (or a precedent) on their results, mitigating the chance of being 'scooped'; • Breakdown of the silos that traditional journals uphold, by exposing us to broader research than we might encounter otherwise, and giving a home to works that do not have a clear destination in a traditional publication; • Research to be more open and transparent, with the intention of improving the overall quality, integrity, and reproducibility of results.