Potential of Multi-resolution Satellite Imagery Products for Scale Variant Topographic Mapping

Satellite imagery is an important source for mapping of inaccessible terrain where ground control points (GCPs) are not available. This paper attempts to arrive at a trade-off between spatial resolutions of satellite products versus desired mapping scale (1:250 K to 1:5 K) through a case study around Gadra, Rajasthan, India. The products considered for evaluation of geometric accuracy and topographic mapping capabilities are Worldview-2 (WV), Cartosat-1, ASTER (GDEM and corresponding Imagery) and SRTM DEM with Google Earth image (GE). The methodology developed for co-registration of DEMs based on corresponding imageries could bring all the DEMs to a common framework for further evaluation. The results indicated that WV products can be used for 1:10 K scale mapping. However, Cartosat-1 RPCs require a few GCPs to make it suitable for 1:25 K scale mapping, and GE images can be utilized as an aid for feature identification. Although the open-source ASTER and SRTM DEM has good accuracy, their utilization is questionable due to coarse spatial resolution. For inaccessible terrain, small blocks of high-precision WV products may be utilized to derive prospective/possible GCPs for bundle adjustment of Cartosat blocks. The strategy can be adopted for inaccessible terrain mapping of large area without compromising precision at a reasonable budget.