Long Strip Modelling for Cartosat-1 with Minimum Control

Cartosat-1 satellite, launched on 5 May 2005, is designed to deliver high-resolution spatial data of better than 2.5m in stereo with ~27 km swath. The twin panchromatic cameras (Fore & Aft), with a fixed base-to-height ratio 0.62, image the terrain through alongtrack stereo almost simultaneously. The primary mission goal of this Indian satellite is to generate Digital Elevation Model (DEM) of a geographic region of interest (e. g. country) to facilitate the user communities of remote sensing and cartography. Space Applications Centre, ISRO, India has developed & demonstrated a technology to extract DEM from Cartosat-1’s high resolution stereo data based on geometric modelling of long stereo strips using a few Ground Control Points (GCPs). This geometric modelling technique has been termed as Stereo Strip Triangulation (SST) for which dual camera space resection software is the core. It utilizes GCP observations from Fore & Aft cameras and rigorous photogrammetric imaging geometry model in order to update spacecraft attitude parameters to the geometric accuracies of < 15m in planimetry. The SST technique is advantageous due to robustness of modelling and reduction in GCP requirements. The reason is that, the same GCP is visible in both Fore & Aft images; thereby a single GCP contributes to two observations in the modelling process simultaneously. In addition to the updated satellite orientations, DEM over a strip as well as Triangulated Control Points (TCPs) are the outputs of SST software.This paper presents the outcome of the exercises aimed at demonstrating the SST performance for (i) modelling long stereo strips and (ii) extension feasibility of the model over those imaged areas which are devoid of GCPs. * Corresponding author.