Study on sensor's radiometric and temporal resolution requirements for crop monitoring

Abstract

Effects of various sensor parameters sucb as spatial resolution, sensor radiometry and temporal resolution on crop monitoring on resional scale is reported. Results were interpreted for selection of optimal sensor parameters for Advance Wide field sensor (WiFS) sIated for regional crop discrimination and high repetivity monitoring. Analysis was carried out using sensors on board IRS platforms (LISS-I, LISS-II, LIS- III. WiFS, MOS-B) and NOAA -AVHRR wbich covers spatial resolution from 23 meter to 1 km, Radiometry from 7 bit to 16 bit and temporal resolution from single day to 24 days. Requirement of spatial resolution of the sensor for crop identification/classification was evaluated based on the field sizes, local variance and crop classification accuracy. For crop discrimination and mapping of 2-3 ha field sizes. it was observed that spatial resolution of better than 70 meter would be needed. Sensor's radiometric influence was assessed on crop separability, classification accuracy and precision of crop NDVI. For monitoring the crop NDVI at precision better than 1 %, Radiometric resolution NEΔp better than 0.3 % is suggested. Temporal resolution was assessed in reference to requirement of date of acquisition at peak vegetative stage and noise equivalent shift from peak (NEΔtp). It was suggested that revisit period of better than a week is needed for restricting the NDVI error less than 1 % due to acquisition date shift in wheat.