Fully automatic land cover map generation at country scale over France

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Up to now, over France, there is no Land Cover Map generated annually at a decameter resolution.  The Corine Land Cover map, which is widely used, is only produced every 5 years, and 2012 version was issued in 2015. This map is mainly produced using photo interpretation, and therefore requires a very large amount of work.  The very accurate Land Cover layer from IGN (French cartographic institute), is updated regularly, region wise, over a cycle of 3 to 4 years, and therefore only provides the perennial land cover information. Two other products exist, the Global Land Cover 30m produced at LANDSAT resolutions, et the Copernicus HR layers, but with a quite low quality,  for instance on the Landes forest in France.

 

Thanks to its high resolution observations, Sentinel-2 should enable an automatic generation of land cover maps at country scale. Based on a several years of research at CESBIO,  our project to automatically produce land cover maps over the whole France is gaining momentum. Research efforts are being organised within the THEIA Expertise Center on Operational Land Cover.

 

The first prototype products were computed using the LANDSAT 8 Level 2A data from Theia, pending availability of a whole year of Sentinel-2 data. The first products span over one third of France, and have 15 to 20 classes according to the versions.

 

The land cover maps processor is based on Orfeo Tool Box applications, set to music by Marcela Arias, under Jordi Inglada's direction, and with large contributions of several CESBIO colleagues for reference data collection of for the development of processors.

 

Extract of the version 1 of land cover product, computed using LANDSAT8 data in 2013. Click on the image for an interactive display

Warning :

These prototype products were not created in ideal conditions. The LANDSAT-8 2013 data set starts in April only, as the satellite was not yet operational before. The start of vegetation cycle has been missed. The future operational products will use a complete year of data. Moreover, LANDSAT 8 data do not have the same repetitivity and resolution as Sentinel-2, and therefore, the final map quality is not what we expect from Sentinel-2.

 

However, it is still the same type of data, and their processing needs to overcome the same difficulties. It is therefore a full-scale test of our methodology. And finally, although not as accurate, the maps have the same nature as our final product and should allow users to get a first idea of the products Theia will deliver.

 

These products contain errors and must only be considered as a draft. We release them in order to get feedback on their quality and usefulness. Please tell us how they might be useful to you. Tell us also if you find them too inaccurate, or if there is something missing.

 

Prototype product description and download

These products are delivered under the Open Data Commons Attribution Licence. This license allows you to  :

  • share, copy, distribute and use the data
  • create other products based on the data
  • adapt, change and transform the data

with the following constraint : you have to quote the data source (CESBIO) for any use or distribution of the data.

 

These maps were processed with Landsat-8 Level 2A data (30 m resolution and 7 spectral bands) obtained with a 16 days revisit. The first images were taken on the 1th April 2013, until the 30th december 2013. Due to cloud cover, every point on the surface was observed between 8 and 25 times, 16 times on average. Some zones in the Pyrenees, because of cloud and snow cover were not observed often, and this causes artefacts on the maps.

 

Sentinel-2 images, with a better resolution and repetitivity should allow production of far better quality maps.

These maps are made using a machine learning based on reference data bases which provide land cover on a large set of places over France. The following data bases were used :

  • The European Common Agriculture Policy data base for the following classes :
    • annual crops (winter and summer)
    • woody crops (Orchards, Wineyards, Olive groves)
    • permanent meadows
    • estives and moors
  • Corine Land Cover 2012 for the following classes :
    • Dense habitat
    • Industrial or commercial zones
    • Grassland
    • Beaches and dunes
    • Sea and oceans
    • Mineral surfaces
    • Glaciers and permanent snow
  • IGN BD TOPO for the following classes :
    • Water
    • Persistent forest
    • Deciduous Forest
    • Mixed Forest
    • Woody moor

These data bases can have been based on various time period and be older than the satellite time period. Several versions were released to test slightly different nomenclatures.

V2

The following classes were merged

  • estives-moors and woody moors
  • Mixed forests were removed
  • All classes of orchards, vineyards
  • Inland waters and oceans

Product statistics and display are available here..

The full resolution product can be downloaded here.

Posted under: Applications, CESBIO, In English, THEIA

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