Mapping land cover, soil cultivation and crop establishment for nitrate sensitivity analysis using ERS InSAR data

ADAS, a land and environment consultancy, is responsible for monitoring various government funded agri-environment schemes and satellite imagery is increasingly one of the data sources being used in this task. Current research has examined how ERS Tandem imagery can be used to provide information on land management and crop establishment over the autumn and winter. In winter, catchments are most at risk from nitrate leaching after soils return to full water saturation. Research has shown that ploughing in the autumn (rather than direct drilling) increases nitrate leaching and that an autumn sown crop or winter cover can decrease nitrate leaching. Thus during winter, the area and location of bare soil (particularly ploughed land) influences the degree of nitrate leaching. To successfully model nitrate movements over over catchments requires various parameters including information on the area and location of various land cover types, the presence and degree of ground cover of winter crops and the location of bare land (including evidence of whether this land has been cultivated). To river model requires nitrate various InSAR processing of 4 ERS Tandem pairs from 1995 was used to produce gee-coded multi temporal coherence and intensity images for an area of the Rivers Leam, Cherwell and Great Ouse Nitrate Vulnerable Zone in England. Thematic information derived from these images has been compared with a SPOT XS image and farmer's records collected after the ERS acquisitions. Analysis has shown that the potential for discriminating land cover and bare soil conditions is best achieved by combining multi-temporal coherence and intensity images. Data compression techniques have been used to reduce the thematic information into three channels. Pixel based classification has then been used to map autumn/winter land cover, including identifying cultivated bare soil and variation in the degree of establishment of autumn sown crops.