from PART IV - Applications and Operational Systems
Published online by Cambridge University Press: 03 May 2011
Abstract
VEGETATION data are used mainly for multiple date applications. This implies high-accuracy geometric requirements, especially for multitemporal registration. To comply with these requirements, VEGETATION1 image location is improved by a systematic use of a database of ground control points (GCPs), based on VEGETATION1 chips extracted worldwide. Due to this systematic processing, VEGETATION1 has shown a very accurate and stable geometric performance, ever since its launch onboard SPOT-4 in March of 1998. VEGETATION2, launched onboard SPOT-5 in May of 2002, now complements VEGETATION1 for operational production. It was, therefore, essential to ensure geometric continuity between both sensors. Onboard SPOT-5, a stellar sensor provides high-accuracy satellite attitude, thus enabling high accuracy in the absolute image location. Consequently, it is not necessary to improve VEGETATION2 image geolocation using GCPs. However, it is necessary to perform a fine geometric calibration of VEGETATION2 cameras. This calibration is performed during the commissioning phase using GCPs from the VEGETATION1 database. The monitoring of VEGETATION2 has shown that due to this calibration its geometric performance became at least as accurate and stable as that of VEGETATION1, and that geometric continuity between both sensors was guaranteed. This chapter describes the VEGETATION1 and VEGETATION2 sensors, the method used to build the VEGETATION database of GCPs, as well as the operational method used to register VEGETATION data.
Introduction
The SPOT-4 (Satellite Pour l'Observation de la Terre 4) satellite, launched in March 1998, provides data continuity for high-resolution SPOT data users through its High Resolution in the Visible and Infra-Red (HRVIR) instruments.
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