Data Workflow in CAPAS

Description of the data workflow processes

TRAGSA, as a business case provider in the project, is developing the CAPAS service which aims at publishing  and integrating multi-sectorial data from several sources into an existing data-intensive service, targeting better Common Agriculture Policy (CAP) funds assignments to farmers and land owners. The goal is to leverage the data integration facilities offered by proDataMarket, to better define the funds assignments features in parcels and subplots.

CAPAS is working on an improvement of the efficiency and competitiveness of the existing Spanish CAP (Common Agriculture Policy) service by integrating more datasets, underused at the beginning of the proDataMarket project. To use them as a powerful tool, it was necessary to create and develop new data processing algorithms. Therefore, CAPAS is not only an end-user application. Indeed, it involves data collection, data modelling and data processing techniques.

The CAPAS Business Case is oriented towards the replacement of human-generated  (subjective) data with more objective data that can be collected and integrated from different cross-sectorial sources in an automated way.

At least two external datasets (LIDAR and Copernicus SENTINEL2) are being used to improve the agricultural cadastre Spanish database. The economic value generated by this process and its relation to CAP funds assignment will be evaluated during the next year, in the final phase of the project.

Managing LIDAR data

LIDAR files are a collection of points stored as x, y, z which represent longitude, latitude, and elevation, respectively. This data is hard to process for non-specialists. To use them as a powerful tool to define objectively the parameters of agricultural use of parcels and the presence of landscape elements, a new data processing and treatment algorithm has been created.

This algorithm classifies and groups the cloud of points in order to simplify the huge amount of data. The clouds of points are topologically processed to obtain connected areas as polygons or to maintain them as single points. In conclusion, LIDAR datasets are transformed into new raster and vector files, more popular data types, and easier to be dealt with. The overlaps and intersections of the new datasets produced (as Landscape elements) will define the CAP parameters for a specific subplot or parcel.

Managing Satellite data

The Sentinels are a fleet of satellites designed specifically to deliver the wealth of data and imagery that are fundamental to the European Commission’s Copernicus program. The use of satellite images in CAPAS has already been explained in this blog entry.

Description of the source datasets and result dataset

The main source datasets of Business Case CAPAS and main processes used to obtain output datasets are explained below:

LIDAR files

LIDAR files can be available under two different formats: .las and .laz. The LAS file format is a public file format commonly used to exchange 3-dimensional point cloud data between data users, being LAS just an abbreviation of LASER. LAZ files, due to the big size of LAS files, is the zipped version of the LAS format.

Although developed primarily for exchange of LIDAR point cloud data, LAS format supports the exchange of any 3-dimensional x,y,z tuples. This format maintains information specific to the LIDAR nature of the data while not being overly complex.

Technical description of LIDAR format
Technical description of LIDAR format

In the context of the ProDataMarket Project, LAS files used in the CAPAS business case will just be a collection of points (latitude, longitude, elevation).

Spanish LIDAR information is freely and openly available at http://centrodedescargas.cnig.es/CentroDescargas/buscadorCatalogo.do?codFamilia=LIDAR

SENTINEL files

The information to be used in CAPAS business case is the Image Data (JPEG2000) provided by Copernicus at Sentinels Scientific Data Hub (https://scihub.copernicus.eu/). The description of JPEG2000[1] format is beyond the aim of this blog entry but some general ideas will be described.

Sentinel data are freely and openly available at:

https://sentinel.esa.int/web/sentinel/sentinel-data-access/access-to-sentinel-data

More information and general factsheet at: https://earth.esa.int/documents/247904/1848117/Sentinel-2_Data_Products_and_Access.

SIGPAC Database

SigPAC database is a complex information system that covers the whole Spanish geography and all agricultural activities and others related to Biodiversity and nature conservation.

In regards to SigPAC database, the main datasets produced or modified by CAPAS are:

  • Landscape Elements
  • Parcels and Subplots

The level of accessibility of SigPAC database varies depending on Autonomous Communities. For example, it is open and freely available in Castile at http://www.datosabiertos.jcyl.es/web/jcyl/set/es/cartografia/SIGPAC/1284225645888

Data workflow process for CAPAS

The following data workflow, as shown in the diagram below, illustrates the evolution of the different datasets, their transformations and their integration to generate the final result datasets.

CAPAS Workflow
CAPAS Workflow


LIDAR processing

The Grouping process gathers the LIDAR points using the following rules:

  • Errors, noise and overlaps are not taken into account (Classifications 1, 4, 7 and 12). As a consequence, more than 50% of points are removed from the process.
  • Soil, water and buildings have their own groups
  • Classification 19 is considered as short trees
  • Classification 20 is considered as medium trees
  • Classification 21 are 22 are grouped as tall trees

The result of this process is still a LAS file. The following image shows how LIDAR points (green points) have been processed and classified (Green points as trees, red points as soil, orange and yellow as bushes).

lidar-1

The next steps, such as Rasterization or Vectorization, involve topological rules in order to group the points to generate squares (raster) that would be processed to obtain the final vector shapefile.

The following image shows how LIDAR points have been grouped to create topologically connected surfaces. In the image below, yellow areas are Soil, orange are Bushes, green are Trees. Grey areas and blue surfaces (not present in this image) are Buildings and Water, respectively.

lidar-2

Once the trees class is defined in a raster format by LiDAR data, it wasrefined thanks to Sentinel Data which has more updated information. RGB and NDVI products help to identify which pixels have an NDVI value over 0.5 and it could be detected by RGB product in order to check which pixels represent vegetation areas.

Finally, trees auxiliary layer refined by Sentinel is processed to obtain different configurations:

  • Isolated trees
  • Copses

The final result of the process is a vector ESRI shape file, where the copses layer is a polygon feature type and the isolated trees layer is as point feature type. All of them have a direct correspondence with the landscape elements.

The overlaps between detected landscape elements, currently protected sites of Natura 2000 network and the Land Parcel Identification System allows performing an accurate ecological value report for Spanish crops areas.

LiDAR algorithm allows to obtain more detailed information because the landscape value helps to identify which subplot has more value per parcel, obtaining the following benefits:

  • Farmers will get an economical profit through fund-assignments to maintain these trees forms, and
  • the ecosystem and its species will be preserved.

ecological-value

This Ecological value report has been developed regarding the following queries:

  • Query 1: Surface of Sites of Community Importance (LIC) / subplot area.

Score between 0 and 1.

  • Query 2: Surface of Special Protected Areas for Birds (ZEPA) / subplot area.

Score between 0 and 1.

  • Query 3: Protected Sites Value = Sum of query 1 + query 2. Score between 0 and 2.
  • Query 4: Number of Isolated tree / subplot area. Score between 0 and 1.
  • Query 5: Surface of copses area / subplot area. Score between 0 and 1.
  • Query 6: Landscape Elements Value = Sum of query 1 + query 2. Score between 0 and 2.
  • Query 7: Ecological Value = Sum of query 3 + Query 6.

Sentinel Products generation

In the first place, Sentinel 2 (S2) imagery has to be downloaded from the ESA server. In the automatic download process developed, selection parameters were incorporated in order to download only the imagery that satisfies our quality criteria. Two kinds of products are generated from S2 imagery.

  • Simple products: Those which have been generated with one-date imagery. By an automatic process, TRAGSA is generating RGB products for supporting photo interpretation. Another simple product generated is the Normalized Difference Vegetation Index (NDVI) which is widely used for vegetation monitoring.
  • Complex products: Those which are generated with imagery from different dates. The following four thematic layers are going to be created.
    • Permanent grassland: This layer will be useful to determine photosynthetically active vegetation and non active (unproductive or bare soil) areas. Therefore it will help to monitor the maintaining of existing permanent grassland, which is an agricultural beneficial practice for the climate and the environment (REGULATION (EU) No 1307/2013).
    • Herbaceous and woody crops: By using decision algorithms, different crops can be identified. The results will be displayed in two different layers, one for herbaceous crops and other for woody crops.
    • Change detection layer: This layer will highlight areas where changes have happened. The layer will be focused on forests and grassland areas in order to detect dramatic changes, such as those caused by logging or forest fires, as well as to detect more subtle changes associated with AIS (Alien Invasive Species), diseases and reforestation.

Hitherto, only one of the twin S2 satellites (Sentinel 2A) has been launched. When the second satellite (Sentinel 2B) is on orbit, the revisit time at the equator will be 5 days which results in 2-3 days at mid latitude. This high revisit time will offer a quicker updating of SigPAC database in comparison with current updates that are based on low precision data (LANDSAT and SPOT5 satellites) or ortophoto flights generated by each Autonomous Community.

Final Result

As stated previously, Common Agriculture Policy funds Assignments Service (CAPAS) is a set of tools that improves the existing Common Agriculture Policy service (CAP), in order to innovatively manage and upgrade the CAP database provided by Spanish Administration to farmers and land owners. It is important to note that this CAP database is one of the main pillars of the CAP funds calculation systems. As mentioned earlier, the improvement process is based on the leverage of new cross-sectorial data sources from different fields and geographical areas, and the result datasets will be also available at the proDataMarket marketplace.

To use these new datasets as a powerful tool to define objectively the parameters of agricultural use of parcels, presence of landscape elements or temporal evolution of crops, the explained data processing and treatment algorithms have been, at the moment, partially developed.

As a summary, the usage of LIDAR files modifies some Parcel and Subplots features, and SENTINEL images will improve the definition of Parcel and Subplots land use and its temporal evolution.

The new datasets produced by CAPAS using those external sources will be RDFized and incorporated to proDataMarket platform. Therefore, Spanish rural property data, improved using new and underexploited datasets, will be accessible through proDataMarket platform providing the users with advanced visualization and querying features.

[1] JPEG 2000 (JP2) is an image compression standard and coding system. It was created by the Joint Photographic Experts Group committee in 2000

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