An Integrated Approach for Topographical Mapping from Space Using Cartosat-1 and Cartosat-2 Imagery

Topographical mapping constitutes an integral component of the process of managing land resources, and mapped information is the common product of analysis of remotely sensed data. High resolution space-borne remote sensing image data show a high level of detail and provide opportunities to be integrated into mapping applications. For mapping, the geometric potential and also the information content in the satellite images are important. Today Cartosat-1 provides the along track stereoscopic coverage at 2.5 m resolution globally while Cartosat-2 acquires images at less than 1 m which is comparable to any of the globally available high resolution satellites. Topographic maps are designed to be a multi-purpose base maps and typically depict a variety of map features on the landscape on a particular scale. A topographic map contains terrain, forest, vegetation, roads, lakes, buildings, and geographic names. From Cartosat-1 data, terrain (DEM) can be extracted while the achieved accuracy of the DEM is depending upon the pixel size, the base to height relation, the contrast and slope of the area, but also the time interval between imaging both scenes. On these parameters of accuracy Cartosat-1 fits perfectly. The other information content (vizforest, vegetation, roads, lakes and buildings) have been extracted by Cartosat-1 stereo images (3-D feature extraction) and further can be supplemented by Cartosat-2 (2-D feature extraction). DEM generated from Cartosat-1 data is being used for ortho-rectification of Cartosat-2 data. Older maps, City/district maps and Mobile mapping system (Palmtop & hand held GPS) are the other sources to collect the geographic names. There is a tremendous reduction in the ground truth data collection (field verification) by using Cartosat-1 and Cartosat-2 datasets together. The accuracy and morphologic information contents in both the satellites are sufficient for most of the mapping application.This paper describes a methodology to generate/update 1:25000 topographical map using Cartosat-1 and Cartosat-2 images in an integrated approach. This approach include data pre-processing, modeling of space imagery, DEM and Ortho-image generation with or without GCPs, accuracy improvement of DEM and Ortho-image, Image to Image registration, 2D and 3D feature extraction and mapping in a standard cartographic environment. This study also provides a guideline for the 2D or 3D extraction for different feature types.