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TitleOn-Site Interactive Ground Control Collection Using GPS and Geometric Modelling
AuthorCheng, P; Toutin, Th
SourceASPRS/ACSM Annual Convention and Exhibition, Proceedings, Baltimore, Maryland, April 22-25; 1996 p. 8-16
Alt SeriesEarth Sciences Sector, Contribution Series 20041601
AbstractPrecise orthorectification of imagery requires highly accurate ground control points (GCPs) and geometric modelling. With the latest technological advances in GPS receivers, real time differential correction services, laptop computers, and the ongoing research into geometric modelling at Canada Centre for Remote Sensing, products called GCPWorks and OrthoEngine were developed at PCI to interactively help the user to collect GCPs for satellite and scanned airphoto images, respectively. To collect GCPs, the user goes to the field with a laptop computer and a GPS unit with real time differential correction service. The user loads the uncorrected image onto the laptop computer using GCPWorks/OrthoEngine. For each collected GPS point, the user enters the coordinate into GCPWorks/OrthoEngine and finds the corresponding point on the uncorrected image. After three GCPs are collected, GCPWorks/OrthoEngine will use the built-in geometric model to calculate and report the GCP residual errors. Hence, if error occurs during the GCP collection process, the geometric modelling can detect the error, its direction and its approximated value. The error can then be corrected on-site. This process will save the user time and cost in collecting GCPs. Results will be shown in this paper using different satellite and scanned airphoto images to demonstrate the methodology.

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