Orthorectification of Stereo Spot Panchromatic and Radarsat Fine Mode Data using Orbital Parameters
and Digital Elevation Model
Mohd Ibrahim Seeni Mohd and Shahruddin Ahmad
Department of Remote Sensing
Faculty of Geoinformation Science and Engineering
Universiti Teknologi Malaysia
81310 Skudai
Johor, Malaysia
Tel: (607) 5502906 Fax: (607) 5566163
E-mail: mism@fksg.utm.my
, sahmad@fksg.utm.my
Abstract
Rectification of satellite data using ground control points (GCPs) in a polynomial fit is not practical in areas where well-defined GCPs are limited. This will be the case in many forested areas or in coastal areas. Rectification using orbital parameters of the satellite together with limited GCPs will overcome this problem. This study emphasises on the evaluation of the geometric accuracy of SPOT Panchromatic and Radarsat Fine Mode data using the later technique. The GCPs were obtained by differential Global Positioning System technique with sub-meter accuracy. The accuracy of rectification evaluated using independent check points gave a positional accuracy of 0.4 pixels for SPOT Panchromatic data. The rectification reveals that the optimum number of GCPs is 8 for SPOT Panchromatic data and 10 GCPs for Radarsat Fine Mode data. A digital elevation model derived by digital image matching technique from stereo SPOT Panchromatic and Radarsat Standard Mode data was used to remove relief distortion to produce an orthoimage. The digital elevation model (DEM) accuracy was validated using spot heights derived from contour map in flat and hilly areas. The accuracy of DEM achieved from stereo SPOT data is 26.3 m and stereo Radarsat data is 35.2 m. The final orthoimage of SPOT Panchromatic and Radarsat Fine Mode data was quantitatively evaluated by merging with digital vector data of 1:25,000 scale of the area. The mismatch in details between them is about ±1 pixel.
Keywords
Rectification, Orbital Parameters, Digital Elevation Model, SPOT, Radarsat Satellite Data.
1. Introduction
Rectification of satellite image by polynomial method is widely used since it is simple. However, this method is not practical in areas where GCPs are very limited and also in images where the elevation ranges from flat to hilly areas. The use of orbital parameters can overcome this problem.
Various studies have been carried out using satellite orbital parameters for the rectification of SPOT Panchromatic (Cheng & Toutin, 1997 and Westin, 1990) and ERS SAR data (Cheng and Toutin, 1997 and Keong, 1995). The results from these studies showed an accuracy of 0.3 pixel
