Dirkjan Schokker

Herman Mollenhorst

Gerrit Seigers

Yvette De Haas

Roel Veerkamp

Claudia Kamphuis

Real-time visualization of methane emission at commercial dairy farms

Keywords: Farm, Cow, Methane emission, Real-time, Visualization

The Dutch government has set an objective to reduce greenhouse gasses (GHG) emissions to 116 Mton CO2-equivalent in 2030. The agriculture sector aims for 11-23 Mton of GHG emission by 2050 and thus contributes to this objective. For this sector, the major contributor to the GHG emission in the Netherlands is the dairy sector. Before any mitigation strategies can be enrolled, some key facts need to be measured regarding the GHG emission on a farm. One of these key facts is the establishment of the baseline of GHG emission on a farm (and per cow). For this, we previously have built an infrastructure to measure and collect methane and carbon dioxide (near) real-time on a farm. The next challenges, addressed in the current study, were to (1) combine the private methane data, collected real-time through the infrastructure, with open source weather information, and (2) visualize both data streams for farmers, by developing an application that can be viewed on a web or mobile phone platform.

Introduction

Background

The objective for the Netherlands is to achieve a greenhouse gasses (GHG) emissions reduction of 49% in 2030 (compared to 1990). In 1990, the total GHG emissions were approximately 228 megaton CO2-equivalent. This means that in 2030, the GHG emissions has to be reduced to 116 Mton CO2-equivalent. Five sectors have been indicated, including electricity, industry, mobility, houses, and agriculture. For agriculture the objective for 2050 is to have a 90% reduction, in other words a maximum of 11-23 Mton of GHG emission. To establish a baseline for the methane emission of a farm and of an individual cow, and more importantly to identify the most successful strategies to reduce these emissions, it is necessary to have (real-time) methane data. This continuous monitoring of methane emission from livestock production systems, including dairy farming, is needed to understand which aspects contribute to the methane emissions and to what extent. Moreover, this knowledge is needed to develop mitigation strategies. The available data can be used to visualize the impact of these strategies.

A large intensive research program has been started in 2018 by the Dutch Ministry of Agriculture, Nature and Food [START_REF] Schouten | Agriculture, nature and food: valuable and connected. The Netherlands as a leader in circular agriculture[END_REF], to identify strategies to reduce methane emission in the agricultural-sector. Part of this program involves continuous monitoring of methane, by means of sensor measurements, both at the barn and individual animal level. The research program involves several animal production domains, including dairy farms. Therefore, monitoring of methane takes place at 17 commercial Dutch dairy farms. At these farms, methane is measured by methane analyzing sensors. These socalled sniffers use a nondispersive infrared sensor (NDIR) for methane and carbon [START_REF] Huhtanen | Comparison of methods to determine methane emissions from dairy cows in farm conditions[END_REF]. These sniffers generate a constant analogue signal that is linearly related to gas concentrations. By placing these sniffers in the milking robot, we ensured that all milking cows at a farm were monitored for their methane emission while being milked. To collate these data from several sniffers in the field and to link this information to individual barns and animals we developed a flexible infrastructure [START_REF] Kamphuis | A flexible data architecture to automate collection of (near) real-time methane sensor data at commercial dairy farms[END_REF]. This infrastructure continuously monitors sniffer functioning and data quality to bring loss of data to a minimum, and allows for a cheap but trustworthy data transfer from the sensors to a cloud storage platform (in our case: Microsoft Azure). The infrastructure is also flexible in accepting other types of information. One can think of other sensor data, but also animal and farm data that are often stored in separate farm management programs. Another part of the flexibility of the infrastructure links to the scalability, i.e. handling data from new farms in case the number of farms, where methane is monitored, increases.

In this study we worked on two challenges. The first challenge was to combining the real-time sniffer data, which is private data, with open source weather information from IBM through Akkerweb (www.akkerweb.eu). This combination is important because it is expected that wind and relative humidity affect methane emissions [START_REF] Saha | The effect of external wind speed and direction on sampling point concentrations, air change rate and emissions from a naturally ventilated dairy building[END_REF][START_REF] Schmithausen | Quantification of Methane and Ammonia Emissions in a Naturally Ventilated Barn by Using Defined Criteria to Calculate Emission Rates[END_REF]. The second challenge was to developed a tool that visualizes the incoming sniffer and weather data, two data streams that differ in veracity, for web and mobile applications using Power BI, an interactive tool to visualize data developed by Microsoft (https://powerbi.microsoft.com/).

Objectives

Our objectives were (1) to integrate private methane data with open source weather data and (2) to visualize methane emission data on dairy farms in (near) real-time to in an application for web and/or mobile.

Material and Methods

Infrastructure

Up till now, 18 sniffers were installed at 17 commercial Dutch dairy farms, using the same set-up as described by Huthanen et al. [START_REF] Huhtanen | Comparison of methods to determine methane emissions from dairy cows in farm conditions[END_REF]. These sniffers have a nondispersive infrared (NDIR) sensor, a simple spectroscopic sensor, here used to detect methane and carbon dioxide. The sniffer sends the corresponding values every 30 seconds to the connected Arduino (microchip Atmel SAMD21, 32 bit Arm Cortex Arduino compatible and a uBlox Sara R410M, all NB-IoT bands, LTE-M). Subsequently, the Arduinos were programmed to push the data every 3 minutes to the Azure cloud. This was done via the Internet of Things (IoT) network, to avoid potential problems with low coverage of e.g. a WIFI signal.

In Azure, a Microsoft cloud platform (https://azure.microsoft.com), an IoT hub was built which was subscribed to the data stream, meaning getting and loading the data.

Here, different alerts were coded, for example when the data stream pushed by the Arduino had down-time (out of action) or when measured values were outside a predetermined expected range, the data owner received an email [START_REF] Kamphuis | A flexible data architecture to automate collection of (near) real-time methane sensor data at commercial dairy farms[END_REF]. To visualize the data stream from the IoT hub, we used Power BI (Version: 2.72.5556.801 64-bit, August 2019), which provides interactive visualizations to create dashboards and reports. Additionally, we integrated an additional open data source, i.e. current weather data. Here, we have used the IBM weather data, by querying the current weather via an API at Akkerweb. The following weather fields were retrieved: temperature, wind speed, precipitation (last 24 hour, 6 hour, or 1 hour), UV strength, and the relative humidity. These values were visualized within Power BI for the city in which a farm is located. The associated city names were transformed to "latitude-longitude" by using https://www.latlong.net/, to ensure proper working of the API. An schematic overview of the data flows is presented in Figure 1.

Results & Discussion

Methane visualization

We were able to visualize sniffer data in (near) real-time for individual commercial Dutch dairy farms. A lesson we learned when performing the data push from the cloud Azure to Power BI is that the data needed to be in a so-called "star" schema. The center of the star has one fact table (in our case the farm) and a number of associated dimension tables (in our case methane and weather data). This star schema is needed to have a more efficient performance on the visualization side in Power BI, compared to a so called "snowflake" schema. Figure 2 shows data from one sniffer, equaling methane emission data from one milking robot unit on a farm, for a 90-minute period. This figure shows fluctuations around zero, indicating the absence of a cow in the milking robot. On the other hand, a peak indicates the presence of a cow in the milking robot. From these data, it is not evident yet when one cow enters or leaves the milking robot. It would be worthwhile to combine these sniffer data to other farm management software and/or measurements, to assess more precisely when a cow enters or leaves the milking robot. When further developing this visualization application further development is needed regarding the integration of the individual cow data. The main advantages of such additional data are to have improved emissions estimates at farm level, and the possibility to generate a cow specific methane profile. This will open-up new possibilities to reduce methane emission, by feeding and/or breeding strategies, as well as management [START_REF] De Souza | Mitigation of enteric methane emissions through pasture management in integrated crop-livestock systems: Trade-offs between animal performance and environmental impacts[END_REF].

Integration with additional data streams

The sniffer data may fluctuate due to characteristics of the barn. For example, its construction and air flow through the barn and the location of the milking robot may influence the measurement. Furthermore, outside weather may also exert an influence, like temperature, wind flow, and humidity. The current weather data was pulled into Power BI and subsequently visualized for the village the farm is located (for example Cornwerd, a city in the northern province Friesland, see Figure 3). While developing this part, we experienced Power BI was not yet optimally designed in handling the data streams. Mainly because Power BI is designed to visualize data from data warehouses and the new data was appended to the database. Power BI will load the whole database each time after a refresh. In our case we have combined data streams from private and open data, simultaneously. The methane data stream was loaded into an SQL database in the cloud and subsequently a subset of the data was pushed to Power BI. Power BI was subsequently used to developed a prototype application for both web and mobile (Figure 4). This application now demonstrates the cumulative methane emission per day, which resets every day (122.63K in Figure 4). Additionally, the methane emissions from the last 60 minutes are visualized, as well as the current outdoor temperature (°C), relative humidity (%), and wind-speed (km/h). The current study faced the challenge to combine private data, collected near realtime with open source data. This combining of different data sources, with a variety of formats, scale, and veracity will become increasingly important in the future. For example, when developing digital twins (of e.g., a farm) it can be expected that a plethora of sensors will monitor different aspects of the farm; including individual feed intake, animal health status, animal behavior, and GHG emission. Our study contributed to that future by exploring the possibilities to retrieve data real-time, combine it with open source data, and to visualize it for farmers. Moreover, combining the sniffer methane data with other information like age of the cow, which is a factor known to influence emission [START_REF] Ramirez-Restrepo | Methane emissions from young and mature dairy cattle[END_REF][START_REF] Van Gastelen | Are dietary strategies to mitigate enteric methane emission equally effective across dairy cattle, beef cattle, and sheep[END_REF]. Such information would be an addition to our application, to better interpret the sniffer data or to enrich the visualizations by coloring per age group. In addition, further development is needed regarding the application (web and mobile), particularly to integrate the individual cow data. The main advantages of such addi-tional data is to generate a cow specific methane profile. This will open-up new possibilities to reduce methane emission, by feeding and/or breeding strategies, as well as management [START_REF] De Souza | Mitigation of enteric methane emissions through pasture management in integrated crop-livestock systems: Trade-offs between animal performance and environmental impacts[END_REF].

Conclusion

To reduce the GHG emissions on dairy farms in the Netherlands, it was necessary to first establish a baseline of GHG emissions per farm (and per individual cow). To do so, we built a data infrastructure for real-time collection of methane measurements. Subsequently, we have shown (near) real-time visualization of methane measurements, enriched with open source (weather) data. Visualization is performed on an interface via a web and mobile phone. The current methane data stream is visualized, as well as the cumulative amount of methane per day per farm. Additionally, the current weather data is integrated to enrich the methane data and possibly identify influences, e.g. wind speed, on the methane measurements. The data handling for visualization could be enrolled on 100 farms in the near future.

Fig. 1 .

 1 Fig. 1. Data-flow diagram. The sensor is placed in the area of the milking robot. The data is captured by an Arduino sends it to Azure in the cloud. In Azure the data is loaded into an IoT hub. Lastly the data is visualized in Power BI.

Fig. 2 .

 2 Fig. 2.Results of the last 90 minutes for a single sensor. The x-axis depicts the time, here from approximately 12.30 PM to 2.00 PM. Whereas the y-axis depicts the concentration methane in the air, in parts per million (CH4_PPM).

Fig. 3 .

 3 Fig. 3. Overview of the current weather of a participating farm, here in Cornwerd. The left panel shows the location on the map of the Netherlands, whereby the view is zoomed in on the province of Friesland. The right panel shows the city name, data, time and below the temperature in degrees Celsius and the UV-index. Furthermore, the precipitation of the last hour, previous six hours, or past 24 hours, and the current wind speed, and the relative humidity.

Fig. 4 .

 4 Fig. 4. Prototype of the mobile phone app.

Acknowledgement(s)

This research was conducted by Wageningen Livestock Research, commissioned and funded by the Ministry of Agriculture, Nature and Food Quality, within the framework of Policy Support Research theme "Data driven & High Tech" (project number KB-38-001-004 Smart and Privacy conserving infrastructures). Data used for this study was collected within the Climate Envelop project of Ministry of LNV.


Christos Giovanopoulos

Yannis Kallianos

Ioannis N Athanasiadis

Dimitris Dalakoglou
email: d.dalakoglou@vu.nl

Defining and classifying infrastructural contestation: Towards a synergy between anthropology and data science

Keywords: Infrastructural contestation, Infrastructural gap, anthropology, data sciences

The last decade infrastructure systems have been under strain around the globe. The 2008 financial crisis, the so-called fourth industrial revolution, ongoing urbanisation and climate change have contributed to the emergence of an infrastructural crisis that has been labelled as infrastructural gap. During this period, infrastructure systems have increasingly become sites of public contestation with significant effects on their operation and governance. At stake has been the issues of access to infrastructure, their social and environmental consequences and the 'modern ideal' embodied in the design of those sociotechnical systems. With this paper we apply a cross-disciplinary methodology in order to document and define the practices of this new wave of infrastructural contestation, taking Greece in the 2008 -2017 period as the case study. The synthesis of quantitative and qualitative datasets with ethnographic knowledge help us, furthermore, to record tendencies and patterns in the ongoing phenomenon of infrastructural contestation.

Introduction

The last decade infrastructures have been increasingly noticeable as the terrain of socio-political contestation. Economic crisis, disruptive technologies and ongoing urban expansion -among other reasons -challenge the capacities of even the 'developed economies', to sustain their pre-crisis level of infrastructural provisions. This phenomenon, which has been labelled infrastructural gap [START_REF] Authers | Infrastructures: Bridging the gap[END_REF], [START_REF] Dimitris | Infrastructural gap: Commons, state and anthropology[END_REF], ODI 2016), challenges the modernist ideal of infrastructure development and questions its concomitant model of infrastructural governance. The role of infrastructure systems as safeguards of unhindered economic growth and social cohesion is at stake and has been contested by various movements in diverse forms. A recent example of such contestation has been the Yellow Vest protests in France that were concerned initially with access to automobility, heating, and hydrocarbon-based energy. That movement, besides contesting the infrastructural and environmental policies of the French government, signified the break-up of the social contract between polity and citizenry that is facilitated by these infrastructural provisions. This paper aims (A) to define infrastructural contestation, to create a typology of the phenomenon and to document its diversity and its scale and (B) to show trends and patterns within infrastructural contestation, with Greece as the case study. In order to achieve this, we have compiled datasets of events of grassroots contestation and socio-political struggles related to infrastructures during the 2008-2017 period. In the context of the infra-demos project, which seeks to critically understand the relationship between infrastructures, democracy and civil participation, we analyse these struggles both qualitatively and quantitatively using ethnographically embedded knowledge and digital tools. The latter enriches the affordances and capacities of the ethnographically acquired knowledge by making explicit quantitative correlations. The analysis and visualisation of large data-sets related to infrastructural contestation allow us to conceptualise the various representations of contestation. Moreover, this ongoing synergy between data science and anthropology, although a work in progress, enables us to detect processes towards a more active citizen engagement with infrastructure.

2

The case study and beyond

The global financial crisis had sweeping consequences for infrastructural sustainability and provision within Europe. Increased austerity in public spending as well as privatisation of public assets affected the governance, maintenance and materialities of hard infrastructures 2 . The consequences for soft infrastructures [START_REF] Filion | Contested infrastructures: Tension, inequity and innovation in the global suburb[END_REF] are even more evident, with reductions in funding for social provision and welfare services [START_REF] Dimitris | Infrastructural gap: Commons, state and anthropology[END_REF]). As such, the crisis -paired with neoliberal policieshas challenged the role of infrastructures in 'forming the base on which to operate modern economic and social systems' (Larkin 2013: 330).

Within that context while Greece may have been the most extreme case of crisisstricken country in the EU, it is far from being unique [START_REF] Dalakoglou | Critical Times in Greece: Anthropological engagements with the crisis[END_REF]. The volatile financial recovery and the ongoing political uncertainty across the EU combined with the permeation and effects of disruptive technologies around the globe, have upset the foundations and legitimacy of the dominant infrastructural model. At the same time, infrastructural contestation has emerged as one of the main socio-political phenomena through which austerity, neoliberal policies, environmental risks and state legitimisation have been challenged.

Roads and other transport networks, water and sewage systems, communication and electricity networks, as much as welfare and state governance infrastructures have been subject to social dispute and conflicts. In addition to the aforementioned Yellow Vest protest against the allegedly pro-environment fuel tax and access to automobility, heating etc. in France , one can also mention the dynamic protests against the increase in public transport fares in Chile (2019), the water charges battle in Ireland (2015-16), the re-municipalisation of water systems (e.g. Paris 2010, Berlin 2013, Budapest 2012 and many more EU cities), the ongoing No-TAV movement in north Italy, struggles against the construction or expansion of airports (ZAD, France; Gatwick, UK) or for the utilization of former airports (Tempelhof, Berlin).

Making explicit the multifarious ways in which similar socio-political mobilisations contested infrastructure systems and flows in Greece during the same period provides insights and a method that can inform research in different frameworks. Those movements have rendered the infrastructural domain as one of the most important public sites of civil participation. On the one hand, they made visible power relations embedded in the technologies, governance and distribution of infrastructure systems, allowing their re-conceptualisation. On the other hand, the diverse (traditional and novel) modes of engagement with infrastructural systems arguably underline the potential for emerging, innovative and democratic forms of infrastructure participation.

Mapping infrastructural contestation

Our engagement with previous studies on the infrastructural gap and political mobilisations (Crisis-scape.net 2014, Dalakoglou & Kallianos 2014, 2018; Giovanopoulos & Dalakoglou 2011) and pilot ethnographic fieldwork on sites where infrastructures were contested (solidarity schools and clinics, waste management, energy communities) provided us with an empirical understanding of the significance and wider dynamic of infrastructural contestation. Thus, before proceeding to more precise and longer-term ethnographic fieldwork the need for systematic documentation of the phenomenon, its taxonomies and scales and by extension for a more precise definition of its content in practice became explicit to us. Our mapping focuses on the grassroots aspect of infrastructure contestation and is composed by four dimensions: 1.) a description of instances of socio-political antagonism in regard to infrastructure; 2.) the different types of those events according to their means of struggle/form of action; 3.) the infrastructural fields those conflicts regard; and 4.) the mode of infrastructure contestation each of the events relates to. Our aim has been to depict the realm of socio-technological interventions from below and highlight comparisons between them in order to visually explore patterns and draw some preliminary conclusions.

Method

In order to collect and digitise our dataset, we followed seven stages.

1. By building on thick and deep datasets acquired from our previous and pilot studies we created a broad but systematic timeline of socio-political conflicts that took place between 2008 and 2017. We did so according to their documentation in communication hubs (online media) of social movements. This initial timeline operated as guideline in outlining the two next steps. 2. While we confirmed the high degree of conflicts related to infrastructure at this point our research lacked a definition of the infrastructural fields at play. Thus we proceeded in their classification to specific categories (Table 1 events that occurred around and were related to, to a greater or lesser degree, the infrastructural fields that we defined. Thus we formed the initial chronological line-up of instances of infrastructural contestation which constitutes the first dimension of our mapping. 4. We proceeded then in defining the second dimension of our mapping. This regarded the variation of the struggles and mobilisations related to infrastructures according to the means and kind of practices they employed. We classified the events in six categories: i. strikes & protests, ii. civil disobedience campaigns, iii. community struggles, iv. (infrastructure) self-management or recuperation, v. institutional and legal interventions and vi. generative endeavours linked to infrastructuring attempts. Such categories are not mutually exclusive. An event may involve more than one type of action. Analytically they are important because they indicate the connection between types of socio-political and infrastructural contestation. Most significantly they point out to the subjects and processes that are more prone to contest critically infrastructure systems. In addition, we drew a last category to include 'general events', mainly general strikes, that interacted with more specific and targeted movements around infrastructure. 5. The following step was to classify the recorded events according to the different ways in which they engage with and contest infrastructure. Thus, we defined a typology of infrastructure contestation (see Section 4 below), which forms the third dimension of our datasets. Central to the definition process has been the degree with which movements, forms of struggle and demands problematise, or not, the existing infrastructure paradigm. 6. Building on these initial findings and definitions we continued with a more thorough, focused and detailed search of events of infrastructural contestation. Our aim was to cover and map to the largest possible degree movements, campaigns and citizen initiatives which engaged with infrastructural contestation. This effort resulted in a list of 880 events. 7. The last part included the revisiting of our taxonomy of infrastructural contestation. Considering issues that were raised by the larger volume and variety of events and types of action that challenged the established infrastructure arrange-ments, we refined our definitions and typology of infrastructural contestation (see Section 4). Health care (hospitals, etc.) Social security (insurance -pension system) Education (schools, universities, etc.) Housing (temporary shelter) Recreation (parks, coastlines, public spaces, etc.)

Sources

The collection and composition of the datasets was one of the most challenging parts of the process. This was due to the magnitude of mobilisations that occurred in this period, due to the lack of any consistent recording of socio-political struggles 3 in Greece and due to the informal status of many of these grassroots movements unlike elsewhere in Europe (Institute of Citizen Studies, 2016). While our mapping of events of infrastructural contestation is by no means exhaustive, we attempted a double task. First, to certify the validity of information regarding the events we documented. Second, to achieve a degree of representativeness in relation to the array of movements that emerged around infrastructure during this period. In order to achieve this, we proceeded as follows:

1. By combining our initial mapping of socio-political antagonism and our ethnographically acquired knowledge we made a list of the movements and campaigns related to infrastructural contestation. This assisted a more focused research for, and use of, sources. From those datasets we retrieved the vast majority of infrastructural events related to labour strikes and protests. 3. In order to pin down the diffused activity of informal movements on infrastructural fields we scanned online hubs of social movements (athens.indymedia.org and kinimatorama.net) and hubs of the alternative and social solidarity economy (enallaktikos.gr and solidarity4all.gr). Through these sources we documented specific actions of grassroots infrastructural contestation and we identified struggles and initiatives which we then confirmed and explored more via other avenues. 4. The online media hubs (webpages and blogs) of movements and campaigns, 12 in total, and the online outlets and social media of citizens' initiatives which engaged in infrastructural contestation, 73 in total, have also been a significant source. These sources covered a big portion of campaigns (e.g. against mobile phone towers, road tolls and public transport price-hikes), of specific struggles related to infrastructure (e.g. against landfill construction in the town of Keratea, antiprivatisation struggles, or against mergers of public hospitals and schools), as well as of initiatives that created their own alternative infrastructures (e.g. solidarity clinics and schools). 5. Lastly, we resorted to an open internet search in order to retrieve information for specific events of infrastructural contestation that we had already identified. These sources included articles from the online editions of 11 newspapers with nationwide distribution, 32 regional and local media outlets, 9 online media sources, 3 special interest media, and 8 alternative media sources. In total 63 different sources.

While we acknowledge that our mapping is not exhaustive, by collecting and crosschecking between these sources we believe that our dataset offers a representative sample of the events and features of infrastructural contestation. However, we should also be attentive to unbalances between forms of infrastructural contestation that may be linked to the choice, or lack, of sources. The systematic recording of labour struggles by the trade unions' institute INE-GSEE for example may have contributed to an over-representation of infrastructural contestation related to labour issues and working conditions. We tried to counter such unevenness by performing a meticulous documentation of the informal and decentralised movements. We did this by using alternative media, and mainly their own sources, to record infrastructure related actions. In any case, judging by our findings, any such unbalance does not contradict our initial hypotheses for the increasing importance of infrastructural contestation, and for the growing tendency towards participation and reconfiguration of the existing infrastructural arrangements.

Modes of infrastructural contestation

Suggesting a typology of the modes of infrastructural contestation has not only been the most demanding task but also critical for the conceptualisation of infrastructural contestation. In order to explore the diverse characteristics that defined infrastructural contestation during the examined period we organised a typology based on the following criteria: a. the ability to render infrastructure space as a site of socio-political antagonism, b. the relationship between the expressed demands or actions of a movement, community or public and the infrastructure's function or transformation, c. the form that this contestation has taken in relation to the operation of infrastructure (disruption, remodification, alternative use, innovation, etc.). Based on the facts gathered so far, and on ethnographic affinity and knowledge we argue that we encountered at least six modes of infrastructural contestation.

Contestation of labour and working conditions

Industrial actions in defense of labour rights and income (social security, pensions etc.) and resisting the deregulation of the labour market -which often involves technological changes -compose this type of contestation. Although most times this type does not explicitly refer to infrastructure per se, nevertheless it is central to the disruption (and efficacy) of infrastructural function and provision. According to Pasternak and Dafnos (2018: 740) '[T]he timely circulation of goods, services, information, resources, and energy through territory is critical to capitalism today, rendering acute the problem of blockades and resource extraction stoppages for the state'. Moreover, the attempts to restrict this disruptive power held by infrastructure employees (even by manual non-specialised workers) has often led to infrastructural 'innovation' (automation, robotics etc.).

Contestation for the right to access

This type concerns struggles for a fairer distribution of, and access to, infrastructure networks that are fundamental in sustaining everyday life (water, energy, transport etc). This mode may interweave with demands for public investment on infrastructure development. It also relates to acts of civil disobedience for access to infrastructure (e.g. clandestine power connections) or with resisting unfair payments for infrastructural services (e.g. refusal to pay transport fares or road-tolls). Such actions have a very direct result in asserting the right to infrastructural use. However, while contestation over access accentuates the injustices in the distribution of infrastructure networks it does not always prompt a questioning of the infrastructural model. Yet, in specific contexts, such contestation type may cause growing financial leakages in infrastructural systems (power-grid, water supply, road system etc.) and thus enforce changes in the governance and operational mode of the infrastructure at stake.

Ownership & governance contestation

Modes of ownership and governance are among the most contested issues when it comes to infrastructure. The primarily state-funded and run infrastructural model of modernity has been under attack from neoliberal policies and governance the last 50 years [START_REF] Marvin | Splintering Urbanism: Networked Infrastructures, Technological Mobilities and the Urban Condition[END_REF]), yet, the defense of infrastructures as public assets constitutes one of the most prominent types of infrastructural contestation still. Antiprivatisation struggles compose the majority of such kind of contestation and occurred in most of the large infrastructural systems in Greece (telecommunications, ports, energy etc.). Most of the times they blend with other modes of infrastructural contestation, usually labour strikes or struggles for the re-municipalisation of infrastructural provisions (e.g. water).

Contesting infrastructural effects

Here contestation usually concerns acts by local communities and movements against the social, environmental and financial effects of infrastructural development in a vicinity. Mobilisations against waste landfills, river dams, mobile phone towers, and industrial scale air-turbines are some examples of this kind of contestation. While such movements develop, largely, a critique of the top down developmental model in situ (within a local context), it is less often the case to see them moving on a wider critique of the infrastructure model itself. In addition, there are cases that refusal to infrastructural development has been associated with maintaining the local, traditional infrastructure and use (or disuse) of natural resources. However, those rebuffs should not be easily classified as a Not In My Back Yard approach, since they inform a critique of a wider economic and political framework of governance. There are examples (e.g. waste management) where movements and communities proceeded from denial to form their own proposals for alternative waste infrastructure system.

Contestation as remodification of infrastructure

Such form of contestation regards numerous collective and individual, but widespread, everyday uses of infrastructural systems that prompt their remodification. It involves cases in which a specific infrastructure is used by the public for purposes other than the ones which it was initially designed for [START_REF] Filion | Contested infrastructures: Tension, inequity and innovation in the global suburb[END_REF]. In this way a certain level of re-purposing of the specific infrastructure takes place. Most of these cases unfold at the everyday molecular level. However, this type of contestation may also include collective attempts to transform the function and use of an infrastructure. Cases where public 'brown fields' were converted into parks, self-managed recreational spaces or urban-farms are some examples of contestation as remodification in Greece.

Transfigurative contestation

This last type includes movements and attempts which experiment, design or develop alternatives to the dominant paradigm infrastructure with regard to engagement in acts of infrastructuring. Transfigurative contestation does not concern only attempts for more inclusive and equal redistribution of infrastructural provisions. It regards experimentation with infrastructure prototypes which aim to organise and facilitate processes of social transformation. In that sense it refers 'to infrastructure' as verb and not as a noun. It expands 'the right to infrastructure' from merely a meaning of 'access to' to a concept that claims the right to create infrastructure (Corsín Jiménez 2014). Thus, it opens up the notion of infrastructural contestation to participatory experiments of design in a process of democratisation (and commoning) of infrastructural systems. Examples of transfigurative contestation in Greece include selforganised solidarity clinics, solidarity schools, cooperative hydroelectric power-plants and/or renewable energy communities.

Having defined these six types of infrastructural contestation, according to our data and findings, we need to clarify a few points. First they are not mutually exclusive. This typology is proposed for analytical reasons and it aims to unveil how different agencies, interests and publics affect the technologies and operation of infrastructural systems. Thus many acts of socio-political contestation entailed more than one type of infrastructural contestation. More importantly, a particular struggle could evolve and include many different forms or instances of infrastructural contestation.

Open data and digital visualisation

We have compiled a dataset that includes about 880 grassroots socio-political encounters with infrastructure, that span from 2008 to 2017. Some events existed in an instant in time (as in the case of one day strikes or one off protests), while others have been assigned a duration that spans across several days (as in the case of the operation of social pharmacies). Thus, events are associated with two dates: a compulsory start date, and an optional end date. However, some repetitive events correspond to long term campaigns (e.g. against the road tolls, or anti-privatisation struggles) but appear as instant events date-wise. Each event is classified in three dimensions: according to the type of struggles and actions it employed, according to the infrastructural field in which it unfolded and according to the mode of infrastructural contestation it indicates. Each event can be associated with more than one types, fields and modes. Data have been organized in a spreadsheet, and will be published using an open license, on Zenodo.

To visualise the dataset, we have employed the Timeline Storyteller [START_REF] Brehmer | Timelines Revisited: A Design Space and Considerations for Expressive Storytelling[END_REF], an open-source expressive visual storytelling environment for presenting timelines in the browser or in Microsoft Power BI. Timeline Storyteller allows us to visualise different aspects of timeline data using a palette of timeline representations, scales and layouts, as well as controls for filtering, highlighting and annotation. The data storytelling approach intends to use quantitative date to convey multiple narrative points, and to explore the process of transforming data into visually shared stories (Lee et al, 2015). An example timeline is shown in Figure 1, where the pattern identified shows that in the beginning of the crisis, during the period between 2008-2009, mobilisations mostly concerned 'against infrastructure effects' events, while from 2010 onwards, there was a rise of 'right to access' contestation events. 1. Looking at the more general trend and mutations of types of contestation we see an explicit tendency from community struggles against infrastructural effects in 2008 and 2009 (Fig. 1), towards civil disobedience in 2011-2012 (Fig. 2) and from there to self-management/recuperation of infrastructures (Fig. 3). While this tendency does not relate to the evolution of a specific event or campaign, it maps a more general trend among various forms of infrastructural contestation. Thus it is reveal-ing of the transformative processes that unfold and of the emerging tendencies for participatory infrastructuring. 2. The majority of the "strikes and protests" type relates predominantly with "labour rights" industrial disputes and to a smaller degree with anti-privatisation struggles (governance & ownership form of infrastructural contestation) and for "right to access" (Fig. 4). This information confirms the weak (and indirect) links of traditional forms of industrial action and the labour movement with transformative infrastructural processes. 3. By taking into account the number of incidents, regularity of appearance and duration of events most present incidents concern labour rights and working conditions, right to access and transfigurative contestation (Fig. 5 and points a. and d. below). 4. The vast majority of cases of transfigurative infrastructural contestation (64 out of 80 events in total, or, 80%) appear on the field of welfare infrastructure. This indicates that it is more likely participatory forms of infrastructuring to occur on the sphere of 'soft infrastructures', which relate to social reproduction and welfare. 5. Almost a tenth of the events documented (84 out of 880) concern "against infrastructural effects" type of contestation. The vast majority of them (75, or, 89%) concern 'community struggles' and largely opposition to the environmental effects of infrastructural development on the fields of waste management, telecommunication (radiation from mobile phone towers) and renewable energy power plants.

Remarks and observations

These initial quantitative observations indicate the favourable areas for more thick description through qualitative enquiry. They also point toward certain directions in order to ethnographically understand better the phenomenon of infrastructural contestation. However, some preliminary points that can be made at this stage by synthesising our mapping and our qualitative thick datasets are: a. While the majority of contestation involving infrastructural fields concerned labour issues (59%) and took the form of industrial actions and strikes, the most lasting infrastructural effect was exercised by other forms of socio-political contestation. Community struggles and mainly the generation of new infrastructures by the solidarity movement were more closely connected to forms of transfigurative contestation (Fig. 1 and point d. below). b. Moreover, in regard to infrastructural contestation around labour and working conditions, one should note the non-direct effect of these struggles on infrastructure systems. The discourse of the social agents involved in these incidents lacked a wider critique of the interrelationship between power structures and the operation of the infrastructure within which they acted. The demands of these struggles predominantly concerned opposition to cuts and privatisation of (public) infrastructure. There have, however, been a few interesting exceptions of the labour issue developing into a critique of infrastructure operation, such as the attempt at self-management of the public hospital of Kilkis.

c. By the same token, only some of the cases of infrastructure contestation associated with the right to access or against the effects of infrastructure development seem to develop a critique of the dominant infrastructural model per se. For example, only recently some of the participants in the decade long struggle against solid waste management in Attica, (Fyli, Keratea and Grammatiko) seem to formulate alternative proposals about the infrastructure systems in question. However, such struggles represent processes of active participation in infrastructure planning, even if they just disclaim any infrastructure development. d. While the number of generative forms of social contestation and of transfigurative paradigms represent a small proportion of instances of infrastructural contestation, they have a much larger time-span and thus transformative capacity. Moreover, qualitative evidence suggests that they include a wider number and variety of actors, users and infrastructural publics [START_REF] Collier | Preface: Public Infrastructures / Infrastructural Publics[END_REF]. In this way they often develop significant (and long lasting) participatory infrastructural potential, as is the case with solidarity schools, solidarity clinics and the few self-managed renewable energy power plants. e. Another significant feature of our method regards the mapping of fluctuations (and interactions) of socio-political mobilisation and incidents of infrastructural contestation. Comparing the two dimensions one notices that they follow a common pattern. Most precisely that in this ten-year crisis period they peak around 2013-2014 and they retreat post-2015. However, a closer look at some parameters, such as time span of an event, provides some interesting qualitative differences regarding the degree that certain forms of mobilisation contest infrastructures and establish accumulatively long-term cases of infrastructural participation. Hence, they constitute examples where novel forms of socio-technical relations and infrastructural citizenship may be incubated.

Conclusions

Today infrastructures are increasingly approached as socio-technical systems that shape and are shaped by relationships of power. The post-2008 crisis besides its material consequences, including a serious gap in infrastructure development in Western Europe, has brought to the fore the socio-political role inherent to infrastructure and, thus, contested nature. A feature augmented by technological developments and environmental concerns. As Hill (2017) mentions the design of life-ecosystems in 21 st century moves towards something "socially powerful: to shared systems, civic systems." In that context, the emerging digital, interactive and open source infrastructures, have to address an array of concerns around which infrastructural publics and users move and mobilise in both urban and rural environments. By composing our datasets on infrastructural contestation we were able to visualise, to grasp, and outline the scale of the phenomenon. It enabled us also to determine and classify more precisely the forms that it takes and to make visible a number of quantitative dimensions with significant qualitative impact on the unfolding process. Such visualisation has also pointed out the social and political significance of certain infrastructure fields, trends and patterns, which can direct the ethnography towards specific sites of deeper research and thicker description regarding the qualities of the phenomenon. Moreover, the results can inform decisions regarding the design of new socio-technical systems and solutions able to register concerns (and also utilize knowledge capacities) of 'non-expert' but equally (in-situ) specialised users and communities [START_REF] Collier | Preface: Public Infrastructures / Infrastructural Publics[END_REF]. In doing so, 21 st century infrastructure systems can not only install (productivity) optimisation sensors but become sentient platforms of the totality of the social and natural life.

The mapping of infrastructural contestation in Greece, despite its focus on grassroots forms of infrastructural contestation -or rather because of it -documented the extended presence of the infrastructural gap that left almost no infrastructural field unaffected. Socio-political tensions have revealed, on the one hand, the infrastructural realm as a contested terrain between a variety of actors and publics; on the other hand, it revealed an increasing number of citizen-led movements that not only fight about or for infrastructure but also over it, namely demand a role to its function and structure. These movements did not refrain from building their own infrastructures where the existing ones failed and thus they should be approached as socio-technical transfigurative attempts.

Within the context of our study infrastructure systems are not only negotiated but emerge as a contested public sphere between differential positions and agencies. At the same time, they also emerge as a plateau of social innovation and participation, as many of our recorded examples demonstrate. Moreover, despite the fluctuations of such transformative endeavors, what it seems established is a permanent process and a variety of practices of infrastructuring, which maintain the potential for a more participatory, democratic and equally distributed infrastructural realm.

A focus on infrastructural contestation thus brings to the fore the variety of societal agents who emerge as constitutive actors in reshaping and recodifying infrastructure, something that challenges the idea that such socio-technical arrangements only become 'visible upon breakdown' (Star & Ruhleder 1996: 113). Events of disruption and blockade of infrastructural flows or acts of contestation that aim towards infrastructural change also manifest, if anything, awareness of both the fragile nature of infrastructure and its critical role in maintaining certain forms of power relations. Hence, when various publics around infrastructures emerge as mobilised subjects they unveil unjust power relations embedded in those socio-technical systems. More significantly, and ever more often, they claim an increasingly active role in their "right to infrastructure" (Corsín Jiménez, 2014) the ecosystems in which they produce and reproduce and the future(s) they dream of.

Fig. 1 .Fig. 2 .

 12 Fig. 1. Timeline of 'community struggle' type of events. (Legend at next page.)

Fig. 3 .

 3 Fig. 3. Timeline of 'self-management/ recuperation of infrastructures' type of events.

Fig. 4 .

 4 Fig. 4. Timeline of 'strike and protests' type of events

Fig. 5 .

 5 Fig. 5. A screenshot of the visualisation of all events as a round timeline, showing different modes of infrastructural contestation in colour

Table 1 .

 1 Infrastructure type categorisation.

	Infrastructure Type	Subcategories
	Transport & Mobility	Airways/ airports
		Bridges & canals
		Public transport (metro, bus, trains, etc.)
		Railways
		Roads
		Ports / sea transport
	Energy	Gas pipelines, storage, distribution
		Oil production, storage, distribution
		Power-plants (oil, coalmines etc.)
		Power-grid
		Renewable energy power-plants (air, solar, water)
	Water	Sewage network
		Water supply network
		Irrigation network
		Dams
	Waste	Solid waste
		Hazardous waste
		Landfill sites
		Recycling plants
	Communication & Infor-	Public broadcasting services
	mation Systems	Telecommunication networks (analogue and digital)
		Media (press, radio, TV, digital)
	Welfare Infrastructures

  2. We looked for existing datasets that cover large parts of grassroots encounters with infrastructure. Those datasets include: the annual report on strikes and labour mobilisations of the Research Institute of the General Confederation of Greek Workers (INE-GSEE) published between 2011 -2017 and unprocessed archival material for the 2008 -2009 period which were made available to us; raw data of Prof.

Serntedakis and Koufidi's research on "Conflictual and electoral cycle in crisisridden Greece" (2018) which cover the years 2009 -2013 were kindly shared with us by the authors.

This study is part of infra-demos project (www.infrademos.net), which is funded by a VIDI grant awarded by the Dutch Organisation of Science, PI: Prof. Dimitris Dalakoglou, Dept. of Social and Cultural Anthropology, Vrije Universiteit Amsterdam.

Between 2006 and 2013 the total drop in the value of infrastructure deals was 80%(Linklaters 2014: 8).

Even the most organised and institutionalised social movements, such as the General Confederation of Trade-Unions of Greece (GSEE), kept records of the labour movement activities only between 2011 -2017.


Luís Sousa

Laura Poggio

Gwen Dawes

Bas Kempen

Rik Van Den Bosch

Luís M De Sousa
email: luis.desousa@isric.org

Computational Infrastructure of SoilGrids 2.0

Keywords: Digital Soil Mapping, High-Performance Computing, GRASS GIS

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Soil is key in the realisation of a number of UN Sustainable Development Goals by providing a variety of goods and services. Soil information is fundamental for a large range of global applications, including assessments of soil and land degradation, sustainable land management and environmental conservation. It is important to provide free, consistent, easily accessible, quality-controlled and standardised soil information. Spatial soil information is often available as maps of soil properties, e.g. pH, carbon content, texture information. Soil is a 3D body and the maps should describe the landscape (i.e. horizontal) variability as well as the vertical (i.e. along the soil depth) variability. Often, such maps are produced using a Digital Soil Mapping (DSM) approach [START_REF] Mcbratney | On digital soil mapping[END_REF], creating a statistical model between the properties measured at known locations and environmental covariates describing the soil forming factors [START_REF] Minasny | Digital soil mapping: A brief history and some lessons[END_REF]. In recent years machine learning methods [START_REF] Breiman | Random forests[END_REF] were used to develop such models. Once the model is calibrated and evaluated, it is used to predict soil properties at non visited locations.

SoilGrids is based on a DSM system that produces geo-spatial soil information fulfilling two main goals: 1) be a source of consistent soil information to support global modelling, and 2) provide complementary information to support regional and national soil information products in data deprived areas. The main target user groups are policy makers and land management services in countries that lack the means to produce such information, as well as scientists developing other models and tools requiring soil data as input.

SoilGrids is of a series of maps for different soil properties following the specifications of the GlobalSoilMap project [START_REF] Arrouays | Chapter three -globalsoilmap: Toward a fineresolution global grid of soil properties[END_REF]. The production of a soil property map consists of different steps: the fitting of a model, the evaluation of that model and finally the prediction for each raster cell at the global scale with a spatial resolution of 250 metres. Six depth intervals are currently considered and prediction uncertainty is quantified. The total computation time required for a single soil property exceeds 1 500 CPU-hours. Parallelisation is therefore fundamental, requiring up to hundreds of CPUs.

This article outlines the computational infrastructure (hardware and software) employed to compute the latest SoilGrids products in a high-performance computing (HPC) cluster, focusing in particular on the parallelisation and the resource management for global DSM modelling.

General Framework

SoilGrids requires an intensive computational workflow, including different steps and integrating different software. SoilGrids is entirely based on open source software. The inputs to SoilGrids currently comprise observations from 250 000 soil profiles and a selection from over 400 global raster characterising soil forming factors: morphology (e.g. elevation, landform), vegetation information (e.g. NDVI and other indices), climate (e.g. precipitation, land surface temperature) and human factors (e.g. land use/cover).

Gathering and harmonising soil profile observations is one of the core workstreams performed by ISRIC, with the World Soil Information System (WoSIS) [START_REF] Batjes | Standardised soil profile data to support global mapping and modelling (wosis snapshot 2019)[END_REF] being its most visible product. These observations are maintained in a relational database hosted by PostgreSQL [START_REF] Momjian | PostgreSQL: Introduction and concepts[END_REF], from which they are directly sourced for modelling. Environmental covariates are ingested into GRASS GIS [START_REF]GRASS Development Team: Geographic Resources Analysis Support System (GRASS GIS) Software[END_REF][START_REF] Neteler | Open source GIS: a GRASS GIS approach[END_REF], thus being automatically normalised to a unique raster cell matrix (of 250 metres cells). Previous SoilGrids releases were computed on the millenary Marinus of Tyre map projection [START_REF] Snyder | Flattening the earth: two thousand years of map projections[END_REF], a popular projection in environmental modelling. However, this projection expands the surface area of the globe by about 60%. With the increasing size of inputs and outputs in SoilGrids, this overhead urged the switch to an equal-area map projection. The Homolosine projection [START_REF] Goode | The homolosine projection: a new device for portraying the earth's surface entire[END_REF] was selected, since among those projections supported by open source software, is the one that best preserves the shapes of lands masses [START_REF] De Sousa | Comparison of FOSS4G Supported Equal-Area Projections Using Discrete Distortion Indicatrices[END_REF]. The size of each output raster was thus reduced in over 10 12 cells.

The general framework of SoilGrids is described in Figure 1. The main steps are:

1. creation of a regression matrix that overlays soil profile data with environmental covariates.

2. fitting of the regression model. Currently this step is based on state-of-theart machine learning methods, able to produce a measure of the uncertainty of the predictions, namely Quantile Regression Forests (QRF) [START_REF] Meinshausen | Quantile regression forests[END_REF]. 3. prediction with the model at global scale.

HPC infrastructure

SoilGrids is currently computed on Anunna, an HPC cluster managed by Wageningen University and Research (WUR). Anunna provides more than 2 000 CPUs in an heterogeneous set of compute nodes. The majority of compute nodes provide 12 GB of RAM per CPU. Storage is managed by the Lustre distributed file system [START_REF] Schwan | Lustre: Building a file system for 1000-node clusters[END_REF].

The Slurm Workload Manager [START_REF] Yoo | Slurm: Simple linux utility for resource management[END_REF] is used to manage the cluster workload. Slurm offers a large range of flexibility. The user may restrict computation to a specific type of node, require an exact number of CPUs to use in parallel, set the number of CPUs required by each process, set a computation time limit, request a specific amount of memory and declare the exact software packages to load at computation time. These settings are defined in a configuration file (the Slurm file), where the user sets the programmes to run and their parameters.

Parallelisation of global scale geo-spatial computations

SoilGrids requires the integration of a number of software. The two key components are GRASS GIS [START_REF]GRASS Development Team: Geographic Resources Analysis Support System (GRASS GIS) Software[END_REF][START_REF] Neteler | Open source GIS: a GRASS GIS approach[END_REF] and R [START_REF] Core | R: A Language and Environment for Statistical Computing[END_REF]. GRASS GIS is used to store the input data and as the engine to control the parallelisation of the predictions. R is used for the statistical modelling, i.e. to calibrate, fit and compute the predictions using the QRF model.

The GRASS GIS mapset and region features are used to set up parallelisation. Location is a directory which contains GRASS GIS mapsets, which are its sub-directories. All data in one location must refer to the same spatial reference system (SRS).Mapsets contain the actual data, they are a tool for organising maps in a transparent way and provide isolation between different tasks to prevent data loss. GRASS GIS is always connected to one particular mapset. Mapsets are used to store maps related to a project, a specific task, issue or subregion. Besides the geo-spatial data, a mapset holds the resolution and extent of the current computational region. In this version of SoilGrids, the SRS used for the GRASS location is the Homolosine projection applied to the WGS84 datum.

Prior to prediction, a global tessellation is created dynamically using the GRASS module r.tile, dividing land masses into square tiles of a given side (Figure 2). Predictions are then executed independently, and in parallel, within each of these tiles. A Slurm file is used to start up each individual prediction process. The prediction process receives as argument the identifier of one of the tiles in the tessellation. The process then creates a temporary mapset, setting its region to the extent of the tile it is tasked to process. The temporary mapset works as a geo-spatial sand box for the prediction process. The prediction process loads data from GRASS within the extent of the tile, as set by the GRASS region. The prediction process is controlled by R software linked to GRASS with the rgrass7 package [START_REF] Bivand | rgrass7: Interface Between GRASS 7 Geographical Information System and R[END_REF]. The result is saved to disk as a GeoTIFF file and the temporary mapset deleted (Figure 3).

Resources management with (sub-)tiling

Prediction models developed with the R language may require a large amount of RAM, i.e. tens of GBs of RAM to execute predictions for a single tile under 1 MB in size. The obvious strategy to tackle memory constraints would be to reduce the size of the tiles used to set up the temporary GRASS mapsets. However, this can soon result in tens of thousands of GeoTIFF files. Such large numbers can be excessive for some file systems, and complicate the functioning of command line tools [START_REF] Koenig | sysconf manual page[END_REF].

In the case of SoilGrids, a different strategy was applied to address resource constraints, i.e. sub-tiling. The prediction process sub-divides the tile in equalsize sub-tiles. Within the temporary GRASS mapset, the prediction process successively sets the region to each of these sub-tiles and invokes the general prediction model. The output computed within each sub-tile is finally saved into a folder named after the prediction tile. The end result is a collection of folders, one per tile, each containing as many GeoTIFF files as the number of sub-tiles contained in the tile.

Assemblage of prediction files

The sub-tilling strategy can result in a very large number of GeoTIFF files. For example, a three-by-three sub-tiling matrix applied to tiles of 200x200 km results in over 50 000 GeoTIFF files covering the globe's land masses. All these files must then be aggregated to produce a single asset, easily manageable by end users. The Virtual Raster Tiles (VRT) format [START_REF]VRT GDAL Virtual Format[END_REF] introduced by the Geospatial Data Abstraction Library (GDAL) is a suitable solution, as it provides a simple and lightweight way to mosaic geo-spatial data. A VRT is in essence a XML file that patches together various contiguous rasters in the same SRS into a mosaic. As the GDAL library is used as I/O driver by most GIS programmes this format is widely supported.

GDAL provides a specific tool for the of creation of VRT mosaics: gdalbuildvrt. It can take as input a file with the list of rasters to include in the output VRT. Another GDAL tool, gdaladdo, can afterwards be employed to create overviews for the VRT. These overviews are stored in a companion file to the original VRT. The end user needs only to point a GIS programme to the VRT file to load the full raster mosaic. With the overviews created, access is fast and fluid at different map scales.

The VRT format is also useful to simplify the re-projection of large rasters. Another GDAL toolgdalwarp -can be applied directly to a VRT file, creating a second VRT file encoding the parameters of the specified output SRS. No transformations are conducted on the rasters themselves, thus a swift operation.

Reproducibility and Portability

The parallelisation scheme described in this article is directly portable to any system using Slurm where GRASS GIS and R can be installed. It is also applicable to any other system relying on a similar scheduling mechanism, such as Son of Grid Engine or Mesos [START_REF] Reuther | Scheduler technologies in support of high performance data analysis[END_REF]. In essence, any system able to spawn processes passing a tile identifier as parameter can be used to reproduce this set up. This solution can also be easily adapted to run on single machines with a large number of CPUs and managed by the GNU parallel tool [START_REF] Tange | GNU Parallel[END_REF].

While GRASS GIS is a key component in the approach described wherewith, alternative software can be used to similar ends. Certain raster formats, like GeoTIFF, store rasters in blocks of constant size. It is therefore possible to parallelise spatial computation on the basis of such blocks. GDAL in particular provides an API that facilitates the retrieval of these blocks. However, some preprocessing might be necessary to guarantee that all rasters stack up, using blocks of equal size and spatial extent. The mapset and region features in GRASS are unique among open source software and perform this stacking of input rasters in a seamless way.

The parallelisation approach reported in this article can be applied to other types of modelling where results can be easily parallelised in space. The tiling mechanism is fully dynamic and independent of the underlying SRS. The size of both the main map tiles and its sub-tiles are parameters to the tiling routine, and expressed in number of raster cells, not map units. It is therefore straightforward to apply with different SRSs and computation extents. The main limitation of this approach is with problems that can not be easily parallelised in space, such as hydrological processes requiring continuity or interactions between catchments.

Fig. 1 :

 1 Fig. 1: General framework of SoilGrids.

Fig. 2 :

 2 Fig. 2: Land masses tessellated with tiles of 450 km in side.

Fig. 3 :

 3 Fig. 3: Predictions occur in parallel in each of these tiles.


Shengping Qian
email: shengpingqian@tongji.edu.cnzhouhy@tongji.edu.cn

Xiaozhi Zhang

Jonny Wu

Serge Lallemand

Alexander R L Nichols

Chiyue Huang

Daniel P Miggins

Huaiyang Zhou

First identification of a Cathaysian continental fragment beneath the Gagua Ridge, Philippine Sea, and its tectonic implications

The tectonic history of the Philippine Sea Plate is essential to understand the tectonic evolution of Southeast Asia, but it is still unclear and controversial. Here, we present the first geochemical data of lavas from the Gagua Ridge (GR) within the Philippine Sea. The GR lavas exhibit geochemical signatures typical of subduction-related arc magmatism. Plagioclase Ar-Ar ages of 123-124 Ma, as well as subduction-related geochemical signatures, support the formation of GR lavas in the vicinity of an arc during the Early Cretaceous induced by subduction of the oceanic plate along East Asia. The ages of trapped zircon xenocrysts within the GR lavas cluster at 250 Ma, 0.75 Ga and 2.45 Ga, and match well the ages of zircons recovered from the Cathaysian block, South China. Our results imply that the GR basement is partially comprised of continental material that rifted away from the Eurasian margin during opening and spreading of the Huatung Basin (HB). The depleted mantle wedge-derived magmas evolved and picked up the continental zircons during ascent. The youngest zircon ages and the GR lava Ar-Ar ages (~123-124 Ma) presented in this study newly constrain an Early Cretaceous age for the HB. Our study provides further evidence that the HB is a remnant of a Mesozoic-aged ocean basin that dispersed from South China during the Cretaceous. Transport of continental slivers by growth and closure of marginal seas along the East Asia margin may have been more prevalent than previously recognized.

INTRODUCTION

The Philippine Sea Plate (PSP) is composed of a mosaic of marginal basins, and is almost completely bounded by subduction zones that involve the Eurasian/Sundaland plates to the west, the Pacific Plate to the east, and the Indo-Australian Plate to the south (e.g. [START_REF] Hall | Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations[END_REF]. Tectonic studies of the PSP have a profound influence on the origin of marginal seas, and plate tectonic reconstructions for vast areas of Southeast (SE) China, SE Asia and western Pacific regions since the Cretaceous [START_REF] Hilde | Origin and evolution of the West Philippine Basin: A new interpretation[END_REF][START_REF] Hall | Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: computer-based reconstructions, model and animations[END_REF][START_REF] Sibuet | East Asia plate tectonics since 15 Ma: constraints from the Taiwan region[END_REF][START_REF] Hsu | An introduction to geodynamics and active tectonics in East Asia[END_REF][START_REF] Zahirovic | The Cretaceous and Cenozoic tectonic evolution of Southeast Asia: Solid Earth[END_REF][START_REF] Lallemand | Philippine Sea Plate inception, evolution, and consumption with special emphasis on the early stages of Izu-Bonin-Mariana subduction[END_REF][START_REF] Wu | Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods[END_REF][START_REF] Huang | Potential role of strike-slip faults in opening up the South China Sea[END_REF]. Although some portions of the PSP are better-studied and show oceanic basins and ocean island arc lithosphere of Early Cretaceous to recent ages [START_REF] Deschamps | The West Philippine Basin: An Eocene to early Oligocene back arc basin opened between two opposed subduction zones[END_REF][START_REF] Taylor | The West Philippine Basin and the initiation of subduction, revisited[END_REF][START_REF] Hickey-Vargas | Onset of the Indian Ocean isotopic signature in the Philippine Sea Plate: Hf and Pb isotope evidence from Early Cretaceous terranes[END_REF][START_REF] Tani | Termination of backarc spreading: Zircon dating of a giant oceanic core complex[END_REF], other areas are completely undrilled and remain enigmatic.

One such region is the Huatung Basin (HB) and the Gagua Ridge (GR) along the northwestern PSP (Fig. 1), the focus of this study.

The northwestern PSP is composed of two ocean basins: the larger and better-studied West Philippine Basin (WPB), and the undrilled, smaller HB (Fig. 1).

The GR is a bathymetric high between the HB and WPB, occupying a unique position (Fig. 1). Existing interpretations regarding the origin of the GR are diverse, including an uplifted sliver of oceanic crust [START_REF] Mrozowski | Complexities in the tectonic evolution of the West Philippine Basin[END_REF], a former intraoceanic fracture zone [START_REF] Deschamps | A detailed study of the Gagua Ridge: A fracture zone uplifted during a plate reorganisation in the Mid-Eocene[END_REF], WPB-HB plate boundary [START_REF] Deschamps | Evidence for Early Cretaceous oceanic crust trapped in the Philippine Sea Plate[END_REF][START_REF] Sibuet | East Asia plate tectonics since 15 Ma: constraints from the Taiwan region[END_REF], or a relict subduction zone (i.e. westward subduction of the WPB beneath the HB along the GR) [START_REF] Deschamps | The West Philippine Basin: An Eocene to early Oligocene back arc basin opened between two opposed subduction zones[END_REF][START_REF] Eakin | New geophysical constraints on a failed subduction initiation: The structure and potential evolution of the Gagua Ridge and Huatung Basin[END_REF]. Each scenario has wide-ranging implications for HB-WPB interactions and SE Asian plate tectonic evolution and is explored in this study.

Here, we present new Ar-Ar geochronology and geochemistry for GR lavas: major and trace element, and Sr-Nd-Hf-Pb isotope data for the whole rocks; and U-Pb-Hf isotopic and trace element data for zircons from the lavas. Combined with the regional tectonic constraints, our study provides new insights into the nature, origin and dispersal of the GR that elucidate the tectonic evolution of SE Asia.

GEOLOGICAL SETTING AND SAMPLES

The HB is a small ocean basin that has an enigmatic tectonic history. [START_REF] Deschamps | The West Philippine Basin: An Eocene to early Oligocene back arc basin opened between two opposed subduction zones[END_REF] proposed that the HB was near-equatorial in the early Cenozoic and then docked against the adjacent WPB along the GR around ~35 Ma, while Hall (2012) considers the HB to have been near ~20°N latitudes for most of its history. If the HB and Luzon were already juxtaposed by the Eocene, Luzon paleomagnetism similarly places the HB near the equator or even at low latitudes within the southern hemisphere during the Eocene [START_REF] Queano | North Luzon and the Philippine Sea Plate motion model: Insights following paleomagnetic, structural, and age-dating investigations[END_REF]. [START_REF] Wu | Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods[END_REF] follows [START_REF] Queano | North Luzon and the Philippine Sea Plate motion model: Insights following paleomagnetic, structural, and age-dating investigations[END_REF] and reconstructs Luzon-HB to be within the now-vanished marginal 'East Asia Sea'.

The GR is adjacent to an unusual subduction flipping system (e.g. the PSP subducting northwestward along the Ryukyu Trench, and the South China Sea (SCS) subducting eastward along the Manila Trench) [START_REF] Angelier | Geodunamics of the Eurasia-Philippine Sea plate boundary: preface[END_REF][START_REF] Sibuet | East Asia plate tectonics since 15 Ma: constraints from the Taiwan region[END_REF] (Fig. 1). The geophysical data indicates crustal thickening on the order of 12-18 km beneath the GR [START_REF] Eakin | New geophysical constraints on a failed subduction initiation: The structure and potential evolution of the Gagua Ridge and Huatung Basin[END_REF]. Besides, the northernmost segment of this linear GR subducts beneath the Ryukyu trench [START_REF] Deschamps | A detailed study of the Gagua Ridge: A fracture zone uplifted during a plate reorganisation in the Mid-Eocene[END_REF][START_REF] Dominguez | Oblique subduction of the Gagua Ridge beneath the Ryukyu accretionary wedge system: Insights from marine observations and sandbox experiments[END_REF].

Lavas were collected from the GR by ROV Haixing6000 (Fig. 1). Four sites around the highest peak of the ridge were investigated but only those located at the top provided relatively fresh volcanic rocks (Fig. DR1 andDR2A). The lavas are massive and porphyritic, containing clinopyroxene, plagioclase and orthopyroxene phenocrysts (Fig. DR2C andD). Some plagioclases have resorption textures, leaving incomplete and crooked rims (Fig. DR2D).

Detailed petrography of samples, analytical methods, analytical data, and data plots are provided in the supplementary material.

RESULTS

The zircons from the GR lavas show an age spectrum mainly ranging from Cretaceous to Archean, with three prominent population peaks at 250 Ma (n=13), 750 Ma (n=24), and 2450 Ma (n=14) (Fig. 2B). The zircons display a wide range of ε Hf (t) values, from -31.0 to 23.8 (Fig. 2A), corresponding to highly variable crustal model ages (T DM C ) between ca. 382 Ma and 3015 Ma (Table DR4), consistent with a heterogenous source. Plagioclases in the GR lavas yielded weighted Ar-Ar mean ages of 123.99 ± 0.24 Ma and 124.06 ± 0.27 Ma (Fig. 2E,F).

Generally, the GR lavas show a limited variation in major elements (e.g., SiO 2 :

54.38-56.21 wt.%, total alkalis: 4.32-5.87 wt.%), and are mainly basaltic andesites (Fig. 3A). They are characterized by the enrichment of large ion lithophile elements (LILEs, e.g. Ba, U, K and Pb), resembling the signature of subduction-related rocks from circum-Pacific arcs (Fig. 3B). They all display depleted mantle-type isotopic 15.476-15.493, and 208 Pb/ 204 Pb = 37.961-38.038) (Fig. 3E and Table DR1).

CONTINENTAL FRAGMENT BENEATH THE GR

U-Pb ages of zircons in the GR lavas range widely from 123 to 3035 Ma (Fig.

2A, B

), which suggests that zircon grains are likely xenocrystic. The GR zircons have high U, Th and Y contents and U/Yb values that markedly differ from those of recycled oceanic crust, mantle peridotite and kimberlite, but resemble those of continental crust (Fig. 2C,D). The U-Pb ages and Hf isotope systematics of the GR zircons (Fig. 2A,B) broadly match those of zircon records from the Cathaysian block, South China [START_REF] Yu | Components and episodic growth of Precambrian crust in the Cathaysia Block, South China: Evidence from U-Pb ages and Hf isotopes of zircons in Neoproterozoic sediments[END_REF][START_REF] Li | Detrital zircon U-Pb age and Hf isotope constrains on the generation and reworking of Precambrian continental crust in the Cathaysia Block[END_REF]. The Mesozoic age peak (250 Ma) of the GR zircons can possibly be related to widespread contemporaneous magmatic rocks in South China, while zircon age peaks (~0.75 Ga and ~2.45 Ga) are largely consistent with those for zircons from Cathaysia crust, South China (Fig. 2B). Thus, the GR zircons most likely originated from Cathaysian Block.

The GR zircons are likely inherited from crust-derived material within mantle sources. It is known that crust-derived materials only contain small amounts of accessory zircon. If our zircon xenocrysts are derived from recycled continental crust in the mantle source, the erupted lavas would have continental signatures, e.g., enriched Sr-Nd isotope, due to significantly higher trace element contents of recycled continental crust relative to mantle. However, these features are absent in the GR lavas (e.g. the depleted mantle-like Sr-Nd isotopic compositions) (Fig. 3F).

Furthermore, inherited zircons with multiple episodes of recycling and/or longdistance transport are typically well rounded or ellipsoidal with pitted surfaces. In contrast, most of the inherited zircons in the GR lavas are euhedral to subhedral (Fig. DR3), suggesting no long-distance transport. All the above features argue against the GR zircons being from subducting sediment involving long transport distances or from crust with multiple episodes of recycling.

Alternatively, the zircons in the GR lavas could have been entrained from the Cathaysian crust during magma ascent and/or within the magma chamber. This implies the existence of continental crust beneath the GR. Compared to older continental crust, the GR lavas have remarkably depleted Sr-Nd isotope compositions (Fig. 3F), which suggests that juvenile parent magmas assimilated a small amount of older material to incorporate zircon grains but not enough to dramatically affect isotopic systematics.

PETROGENESIS

As shown in a multi-element spider diagram (Fig. 3B), enrichments in fluid-mobile elements (e.g., U, K, Pb, Sr and Ba) of the GR lavas are typical of subduction-related magmatism. The relatively low Ti/V, as well as high Ba/Yb, of the GR lavas represent subduction-related signatures (Fig. 3C,D). Unlike mature arc systems (e.g. Luzon and Ryukyu Arc), the isotopic compositions of the GR lavas plot far away from the domain of global subducting sediment (GLOSS, Plank and Langmuir, 1998) (Fig. 3E,F,G). In particular, the GR lavas are distributed along the mantle array on the plot of 143 Nd/ 144 Nd versus 176 Hf/ 177 Hf (Fig. 3H), suggesting fairly minor contribution from subducting sediment to the mantle source [START_REF] Plank | The chemical composition of subducting sediment and its consequences for the crust and mantle[END_REF][START_REF] Hickey-Vargas | Onset of the Indian Ocean isotopic signature in the Philippine Sea Plate: Hf and Pb isotope evidence from Early Cretaceous terranes[END_REF]. Additionally, the GR lavas have a typical subducted slab-derived 'fluid' signature with low Nd/Pb (<4.3 relative to ~20 in mid-ocean ridge basalts) (Fig. 3E). In the case of the GR lavas, the elevations of Sr/Th and Ba/La, coupled with the narrow variations of Th/Ce and Th/Yb (Fig. DR4) also underline a significant contribution of slab-derived fluids to the mantle source.

Consequently, we postulate that the GR lavas are derived from depleted mantle that had been metasomatized by subducted slab-related materials Following the approach of [START_REF] Ishizuka | Fluid-mantle interaction in an intra-oceanic arc: constraints from high-precision Pb isotopes[END_REF], a simple simulation shows that the mantle source of the GR lavas was likely to be metasomatized by ~4% fluid derived from altered oceanic crust (AOC) and subducted sediment in a mixing ratio of 50:50 to 90:10 (Fig. 3F andG).

The GR lavas show subduction-related arc geochemical signatures, suggesting a past subduction event. The GR lavas formed by 124 Ma (Fig. 2E,F), which is also consistent with the minimum age (123 ± 1.7 Ma) of zircon in the GR lavas within error (Table DR2). Thus, it is most likely that the GR lavas are derived from a mantle source region metasomatised by slab-derived fluids along South China during the Cretaceous, which was an active margin (e.g. [START_REF] Hall | Late Jurassic-Cenozoic reconstructions of the Indonesian region and the Indian Ocean[END_REF]. In terms of geochemical compositions, the HB lavas have compositions similar to lavas formed in back-arc basin and spreading centers (e.g., Nb, Ta and Ti enrichments, relatively high Nd/Pb and Ti/V, and low Ba/Yb, Fig. 3), while the GR lavas are more influenced by subducted components (the arc or close to rear-arc position).

IMPLICATIONS FOR SE ASIA TECTONIC EVOLUTION

Published geophysical and geochemical data, sedimentation rates, and geomagnetic modeling, show that the HB is likely a trapped remnant of Cretaceous-aged oceanic basin [START_REF] Deschamps | Evidence for Early Cretaceous oceanic crust trapped in the Philippine Sea Plate[END_REF][START_REF] Hickey-Vargas | Onset of the Indian Ocean isotopic signature in the Philippine Sea Plate: Hf and Pb isotope evidence from Early Cretaceous terranes[END_REF][START_REF] Eakin | New geophysical constraints on a failed subduction initiation: The structure and potential evolution of the Gagua Ridge and Huatung Basin[END_REF][START_REF] Huang | Potential role of strike-slip faults in opening up the South China Sea[END_REF][START_REF] Hsieh | The Chimei Submarine Canyon and Fan: A Record of Taiwan Arc-Continent Collision on the Rapidly Deforming Overriding Plate: Tectonics[END_REF]. However, other studies favor a younger age for the HB based on seafloor magnetics and seismology, including Eocene [START_REF] Hilde | Origin and evolution of the West Philippine Basin: A new interpretation[END_REF], Eocene to Miocene [START_REF] Sibuet | East Asia plate tectonics since 15 Ma: constraints from the Taiwan region[END_REF], Oligo-Miocene [START_REF] Kuo | Two-station measurement of Rayleigh-wave phase velocities for the Huatung basin, the westernmost Philippine Sea, with OBS: implications for regional tectonics[END_REF], or mid-late Eocene [START_REF] Doo | Age and tectonic evolution of the northwest corner of the West Philippine Basin[END_REF]. Our study affirms a Cretaceous age for the HB based on our GR lava eruption ages and the youngest zircon ages of ~123-124 Ma (Fig. 2 and Table DR2).

Our identification of a Cathaysian continental fragment in the Philippine Sea suggests that HB formation could be related to rifting of the Cathaysian Block during the Cretaceous, when SE China transitioned from an active subducting margin to extension [START_REF] Xu | Origin of marginal basins of the NW Pacific and their plate tectonic reconstructions[END_REF][START_REF] Zahirovic | Tectonic evolution and deep mantle structure of the eastern[END_REF]. It is also possible that the HB formed during the Early Cretaceous from 131 to 119 Ma [START_REF] Deschamps | Evidence for Early Cretaceous oceanic crust trapped in the Philippine Sea Plate[END_REF]; both cases imply rifting of a Cathaysian continental fragment during the Cretaceous.

Combining published plate models with our results, the HB could be either far-traveled or remained relatively close to Eurasia during its history (Fig. 4). In the far-traveled scenario, the HB was located near South China in the Early Cretaceous, drifted ~2000 km southwards to equatorial latitudes by the Eocene, and then followed the PSP and Luzon ~2000 km northwards after 50 Ma to its present position (Fig. 4).

Southward drift of the HB could be accommodated by opening of a backarc basin or marginal sea near South China, including a large proto-SCS or other vanished marginal seas [START_REF] Deschamps | The West Philippine Basin: An Eocene to early Oligocene back arc basin opened between two opposed subduction zones[END_REF][START_REF] Wu | Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods[END_REF][START_REF] Zahirovic | Tectonic evolution and deep mantle structure of the eastern[END_REF]. Alternatively, a 'short transport' scenario is possible where the HB is a relict proto-SCS fragment that remained relatively close to South China, moved ~500 km southwards during the SCS opening, was captured by the PSP and then moved ~500 km northwards (Fig. 4) [START_REF] Hall | Late Jurassic-Cenozoic reconstructions of the Indonesian region and the Indian Ocean[END_REF]. This scenario requires the HB to be tectonically transported a shorter distance and seems more favorable (Fig. 4), and is still compatible within specific constraints used by far-traveled plate models [START_REF] Deschamps | The West Philippine Basin: An Eocene to early Oligocene back arc basin opened between two opposed subduction zones[END_REF][START_REF] Wu | Philippine Sea and East Asian plate tectonics since 52 Ma constrained by new subducted slab reconstruction methods[END_REF].

Another sliver of Cathaysian-affinity continent has been found within the Luzon Arc basement that apparently drifted southwards during the SCS opening, was accreted and then moved northwards with the PSP during the mid-to late Cenozoic [START_REF] Shao | Old continental zircons from a young oceanic arc, eastern Taiwan: Implications for Luzon subduction initiation and Asian accretionary orogeny[END_REF]. Taken together, we newly present the undrilled HB as a narrow (up to 150 km wide) sliver of oceanic crust, bounded on both sides by continental fragments of Cathaysian-affinity (Fig. 4). Accretion of 'ribbon continents' is fundamental in orogenesis and continental growth over time and space [START_REF] Cawood | Accretionary orogens through Earth history[END_REF]. Our results now show that the transport of continental slivers by growth and closure of marginal seas along the East Asia margin (Fig. 4) may be more prevalent than previously recognized. U/Yb versus Y of zircons sampled from the Gagua Ridge (GR) lavas. For comparison, the zircons from continental and oceanic crust, and mantle peridotite and kimberlite (Grimes et al., 2007 and references therein), eastern Taiwan lavas [START_REF] Shao | Old continental zircons from a young oceanic arc, eastern Taiwan: Implications for Luzon subduction initiation and Asian accretionary orogeny[END_REF] and Cathaysia Block detrital zircons [START_REF] Yu | Components and episodic growth of Precambrian crust in the Cathaysia Block, South China: Evidence from U-Pb ages and Hf isotopes of zircons in Neoproterozoic sediments[END_REF] are plotted. (E-F) 40 Ar/ 39 Ar age spectrum for plagioclase from the GR lavas. DR5). Supplemental Material. Methods, and supplemental figures and Tables. Please visit

FIGURE CAPTIONS

XX to access the supplemental material.

Fig. 1 .

 1 Fig. 1. Geological map of the Gagua Ridge (GR) and adjacent regions. Red star,

Fig. 2 .

 2 Fig. 2. (A) ε Hf (t) versus U-Pb age, (B) U-Pb age histogram, (C) Th versus U, (D)

Fig. 3 .

 3 Fig. 3. (A) Variation of total alkali (Na 2 O + K 2 O) versus SiO 2 , (B) Primitive

Fig. 4 .

 4 Fig. 4. Present-day Southeast Asia map showing possible tectonic journey of the

  Figure 1

  Figure3

ACKNOWLEDGMENTS

This study was supported by the National Natural Science Foundation (NSF) of China (41902044 and 91428207) and the Chinese National Key Basic Research Program (2012CB417300). Jonny Wu was supported by US NSF grant EAR-1848327. We thank editor Prof. Gerald Dickens, reviewer Sabin Zahirovic, and two anonymous reviewers for their constructive and helpful reviews. Stéphane Dominguez is thanked for providing the bathymetric compilation. Shenyang Institute of automation and Zhiguo Qiao are thanked for helping collect the sample. We thank Le Zhang for assistance in the sample analysis.