|Fig 1: Land Cover plus: Crop Map 2015 (pre-production image minus Northern Ireland)|
To the traveller, though relatively small, the United Kingdom is a topographically diverse island with population centres interspersed by the familiar patchwork quilt of the typical English countryside. The patches are fields, in the main a product of a sophisticated cropping system focussed on producing staple crops the colours of which - the bright yellow of oilseed rape in the spring, and golden straws of wheat and barley in the late summer - we are all familiar with. (For the curious the areas of these annual crops can be obtained via the Defra-published statistics.)
What has not been familiar, until now, is how these crops are arranged across the countryside in space and time as seen from a more distant perspective.
As well as being an additional source of statistical data, the new CEH Land Cover plus: Crops 2015 (Figure 1) provides the opportunity to develop a spatial understanding of how the UK’s main arable crops relate not only to each other, but also to their governing environmental factors.
The innovations behind the 2015 Crop Map are the product of a collaboration between the Hampshire-based business Remote Sensing Applications Limited and CEH. Throughout the UK’s 2015 growing season satellite imagery was collected and subjected to a novel processing chain, enabling the development of a library of crop signatures. These have enabled the efficient production of what is probably the UK’s first satellite derived digital crop map.
Figure 2: Detail from Land Cover Plus: Crops 2015 (note, white areas are non-agricultural)
Great Britain has perhaps an enviable record in land use surveying for a range of purposes, notably the Domesday Book in the 11th century, and Dudley Stamp’s Land Utilisation Survey undertaken from 1933 to 1948. Those early surveyors could not have foreseen the technology available today nor its unique perspective.
Those early surveyors could not have foreseen the technology available today nor its unique perspective.
The Crop Map utilises information provided by the European Space Agency’s Sentinel 1 radar and Sentinel 2 optical satellite, providing a new detailed attribution layer to the CEH Land Cover base map's arable and improved grassland land use class. Launched in 2014 and deployed at 693km the Sentinel 1A radar satellite (Figure 3 below) is equipped with a C-band Synthetic Aperture Radar sensor, enabling data to be collected independent of the weather on Earth1. In an orbit of 786km the Sentinel 2a optical satellite carries a multispectral sensor with an imaging sweep or swath width of 290km of the Earth’s surface2.
Figure 2: The Sentinel 1 radar satellite employs Synthetic Aperture Radar. © ESA/ATG medialab3
New insights for agronomy
In relation to agronomy the Crop Map provides a range of new insights. Crops can be considered individually, for example the spatial distribution of oilseed rape across the UK and collectively, as a topographical crop mosaic, illustrating the proximity of different crops to each other and prompting questions on the location of seasonal pulses of agronomic activity and their effects. A number of uses is envisaged for this new data layer: hydrological modelling, catchment-sensitive farming, plant health and crop science, phenology, control of crop subsidies and levies, agri-business, agricultural statistics and climate change4.
Of course the inevitable dynamics of innovation means that many future uses of Crop Map are yet to emerge.
Nicholas Corker, Innovation Manager at CEH
3 Image courtesy of the European Space agency: http://www.esa.int/spaceinimages/Images/2014/02/Sentinel-1_radar_modes. (Synthetic Aperture Radar (SAR) was invented by Carl Wiley at Goodyear Aircraft Company in Goodyear, Arizona in 1951: http://www.lockheedmartin.co.uk/us/products/sar.html)
4 Agricultural Statistics and Climate Change 5th edition 2014: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/337803/Agriclimate-5edition-30jul14.pdf