SPECTRAL VARIATIONS FOR WHEAT OVER ITS CROP GROWTH CYCLE 
Rajendra Kumar Gupta 
D. Vijayan 
S. Prasad 
R.N. Kishore 
T.S. Viswanadham 
National Remote Sensing Agency 
Dept. Training & Educational Activities 
Balanagar 
Hyderabad, Andhra Pradesh 500037, India 
ISPRS Commission VII / Working Group 1 
ABSTRACT 
The paper discusses results of ground based spectral signatures collected using radiometer in IRS and 
LANDSAT/TM (first four) spectral bands for irrigated and rainfed wheat crops over its Crop Growth 
Cycle (CGC). The study was carried out at Chanchak and Dhoolkot areas of Uttar Pradesh (India) during 
December 1990 to March 1991. The variation in computed Normalized Difference Vegetation Index 
(NDVI) for different times of observations at 0930, 1030, 1330 and 1430 hrs IST for IRS and 
LANDSAT/TM has been discussed. The 1030 hrs observation provided a steady and smooth variation in 
NDVI compared to other timings. The irrigated wheat had a little longer period for crop cycle as 
compared to rainfed areas and was observed in both IRS and LANDSAT/TM measurements. A small 
fluctuations in NDVI over irrigated wheat in respects of LANDSAT/TM was observed which could be 
attributed to the weak water vapour absorption in the 0.86-0.90 mm, part of TM band 4 (0.76-090 mm). 
This paper also covers the relationship of these ground based measurements with data acquired for 
IRS/LISS II on five occasions covering the entire Crop Growth Cycle (CGC). 
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