Covariance Propagation in GPS/IMU - Directly Georeferenced Frame Imagery
Mohamed M.R. Mostafa, Joseph Hutton, and Erik Lithopoulos
APPLANIX Corporation
85 Leek Cr.,
Richmond Hill, Ontario
Canada L4B 3B3
Phone: (905) 709-4600
Fax: (905)709-7153
Web: www.applanix.com
E-mail:MMostafa@applanix.com
Abstract
In this paper, an error analysis for the airborne direct georeferencing technique is presented, where integrated GPS/IMU positioning and navigation systems are used in conjunction with aerial frame images for airborne photogrammetric mapping. Covariance propagation technique provides a valuable analytical tool to evaluate different parameters necessary for mapping project design and, thus, it is used to study the expected errors of ground point coordinates when derived from GPS/IMU/image data. The technical specifications of three of Applanix POS/AV airborne positioning and attitude determination systems are used in this study. Two cases are studied in this paper, namely the standard stereo model case and the single photo/DEM case. The stereo case has been already used in standard map production where the aerotriangulation step is bypassed when using direct exterior orientation information measured by the POS/AV systems during image data acquisition. The single photo case is not as widely used, yet provides more economical alternative to the stereo approach, where single photos are processed together with the available DEMs to produce orthorectified quads/images. Different sources of errors are investigated in the present study. Mainly, the effect of the exterior orientation data errors on ground point positioning errors, has been studied for different POS/AV systems and for different GPS accuracy scenarios. The error models are presented and a summary of the results is introduced. In addition to the theoretical analysis, an error analysis is performed to an airborne data set collected in northern California, where the POS/AV system was used to directly georeference aerial frame imagery. The results show that the use of POS/AV enables a variety of mapping products to be generated from airborne navigation and imagery data without the use of ground control.
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