The Rural Payments Agency (RPA) retrospectively publishes crop maps of England each year. Four years of data are now available: 2016, 2017, 2018 and 2019. These maps are derived from Sentinel-1 (radar) and Sentinel-2 (optical) satellite imagery and use a standardised methodology and land cover classification and are comparable one year to the next. Unusually they are presented as a tessellation of vector hexagons of which there are some 32 million hexagons covering England. Each hexagon is between 60 – 80m is size. In this novel format the data are split into Ceremonial Counties which are individually manageable, but for all of England the full data set become almost unusable. This is compounded by its temporal nature with a new full data set being added each year. For this reason the data have been converted to raster format based on the 50 m grid defined by the Ordnance Survey Terrain 50 data set.

Example of CROME Hexagons

The CROME maps use a standard set of land cover classes, although the number of classes has expanded somewhat since 2016. The classes fall into the broad categories Cerial Crops, Leguminous Crops, Energy Crop, Grassland, Non-Agricultural Land, Water, Trees and Unknown or Mixed Vegetation. The individual arable crops, of which there are 70, are not of direct interest to the project. The classes of interest are as follows:

Broad CategorySpecific Class
Arable Crops70 cereal and leguminous crops
GrasslandFA01 Fallow Land
HE02 Heathland and Braken
PG01 Grass
Non-Agricultural LandNA01 Non or sparsely vegetated land
WaterWA01 Water
TreesTC01 Perennial Crops and Isolated Trees
NU01 Nursery Crops
WO12 Trees and Scrub, short Woody plants, hedgerows
Unknown or Mixed VegetationAC00 Unknown or mixed vegetation

For the years 2016 and 2017 the data from RPA are organised as four regional datasets, whereas for the years 2018 and 2019 it is organised into 40 counties. Each dataset has 32,000,000 hexagons, presenting an onerous data management task. To make the data processing manageable the vector hexagons were rasterised into grids based on the 50 m grid cells of the Ordnance Survey Terrain 50 data set. The coordinate space for this is given in the table below. The raster versions are more manageable and amenable to data processing in a raster GIS system.

Bounding Box
BL (0,0)
TR (660,000 660,000)

Raster Version of CROME 2018