MULTITEMPORAL, MULTIFREQUENCY RADAR MEASUREMENTS OF AGRICULTURAL CROPS DURING THE AGRISCATT-88 CAMPAIGN IN THE NETHERLANDS

Multi-temporal, multi-frequency (1.2-17.25 GHz) radar data collected with the DUTSCAT airborne scatterometer over the Flevoland test site in the Agriscatt-1988 campaign, were analysed in relation to crop type and crop growth of mainly sugar-beet, potato and winter wheat. Two frequency ranges were distinguished that had specific backscattering behaviour: the low frequency L-band and the high frequencies X- to K(u)2-band. The L-band had the largest relative content of variation on bare soils and was shown to penetrate potato canopy. The high frequencies, namely the X- to K(u)2-bands, had the largest relative content of variation on crop covers and were shown to be relatively sensitive to canopy structure. These bands were (equally) well suitable for the separation between crop types. All bands were equally useful to indicate qualitatively the growth of beet and potato in the early growing season. The backscattering of wheat appeared not to be related to growth of the crop in any of the frequency bands. The theoretical backscattering model of Eom and Fung was evaluated for its ability to describe radar signatures of crops. It appeared that care should be taken with the representation of leaves as di-electric ellipsoids in the model, notably when the leaf surface is undulating (beet) or composed (potato).