Topographic Map Updation Using Cartosat-1 Data

Indian Remote Sensing satellite Cartosat-1 was launched on 5 May 2005. It has a payload consisting of two cameras one near nadir looking (-5 deg) and the other forward looking (+26 deg) providing the real time stereo data along the track with spatial resolution of 2.5m. These cameras are mounted with a fixed geometry which helps in collecting stereo coverage of the terrain at a fixed B/H ratio of 0.62.The data acquired from onboard SPS, improved star sensor are used for generating terrain dependent Rational Functional Model (RFM). This has opened a new era for Cartographic applications like mapping urban areas and updating of topographic maps for cultural features like local roads, small ponds, group of buildings, play grounds, swimming pools etc. The stereo data from this satellite along with the Rational Polynomial Coefficients (RPC) can be used to generate DEM. For updating of large-scale topographic maps at 1:25,000 or 1:10,000 scale, it requires a planimetrically accurate orthoimage, which is a terrain corrected image, generated using DEM. The positional and height accuracies of Cartosat data products generated using RPC are in the range of 100m to 250m. Differential GPS (DGPS) collected ground control points (GCPs) are used to refine the model and hence to generate more accurate DEM. The same GCPs are used for generation of orthorectified product, which is corrected, for all sensor, camera and terrain related distortions. The satellite data is acquired in perspective projection and processing this data using RPC and GCPs generates an orthorectified data, which is comparable with the orthogonal projected topographic map.