Articles written in Journal of Earth System Science
Volume 118 Issue 1 February 2009 pp 11-26
The inﬂuence of topographic effects in optical satellite imagery is not investigated very extensively in the Himalayan terrain.The topographic variability causes a problem of differential illumination due to steep and varying slopes in rugged Himalayan terrain. Therefore,topographic corrections are essential for qualitative and quantitative analysis of snow cover applications.The present paper discusses the implementation of different topographic correction models on AWiFS sensor onboard IRS P6 satellite images and the qualitative and quantitative comparative analysis in detail.Both the Lambertian and non-Lambertian assumptions have been considered in the present analysis with the aim to explore best suitable empirical model for rugged terrain.The main topographic methods implemented are:
Civco ’s modi ﬁed version of cosine correction
two-stage normalization and
slope matching technique.
Lambertian assumptions are found to be very unrealistic over Himalayan terrain as these lead to either underestimation or overestimation of physical parameters signiﬁcantly both on sunlit slopes as well as the slopes away from the Sun.This problem is overcome by considering non-Lambertian assumption.Minneart constant and C-correction coefficients for all AWiFS satellite bands are estimated using regression analysis.All the results due to topographic effects are investigated qualitatively and quantitatively using four criteria namely visual analysis,validation with ﬁeld measurements (