Abstract
Abstract. The TU Berlin group of the Lunar Reconnaissance Orbiter Camera (LROC) team has implemented a Bundle Adjustment (BA) for spaceborne multi-lenses line scan imagers, by rigorously modeling the geometric properties of the image acquisition. The BA was applied to stereo image sets of the LROC Narrow Angle Camera (NAC) and first results show, that the overall geometry of the stereo models were significantly improved. Ray intersection accuracies of initially up to several meters were homogenized within the integrated stereo models and improved to 0.14 m on average. The mean point error of the adjusted 3D object points was estimated by the BA to be 0.95 m. The inclusion of available Lunar Orbiter Laser Altimeter (LOLA) shots as 3D ground control to the BA, accurately tied to the image space by an aforegoing co-registration, allowed to register the final adjusted NAC DTM to the currently most accurate global lunar reference frame. The BA also provides accuracy assessments of the individual LOLA tracks used for georeference during the adjustment, which will be useful to further assess LOLA derived products.
Highlights
Planetary image data provided by camera systems flown on spacecrafts are used to map the surfaces of distant planetary bodies and to derive digital terrain models (DTMs) and orthoimage maps
4.6.1 Variance Component Estimation: In our Bundle Adjustment (BA) we are dealing with different types of observations and different physical units, orders of magnitude, and precision, e.g. with observed image coordinates at μm scale, projection centers at km scale, rotation angles in radians, and observed Lunar Orbiter Laser Altimeter (LOLA) ground coordinates at km scale
The TU Berlin group of the Lunar Reconnaissance Orbiter Camera (LROC) team successfully implemented a least-squares BA for spaceborne Charge-Coupled Device (CCD) line-scan camera systems that rigorously models the geometric properties at the moment of image acquisition
Summary
Planetary image data provided by camera systems flown on spacecrafts are used to map the surfaces of distant planetary bodies and to derive digital terrain models (DTMs) and orthoimage maps. The fundamental requirement for the exploitation of 3D information from images is the exact knowledge of the camera geometry (interior orientation) and the position and orientation of the camera during image acquisition (exterior orientation) In extraterrestrial photogrammetry, these values are usually provided by a camera calibration under laboratory conditions prior to launch and by Navigation and Ancillary Information Facility (NAIF) SPICE kernels providing the spacecraft ephemerides and camera attitudes as functions of time. These values are usually provided by a camera calibration under laboratory conditions prior to launch and by Navigation and Ancillary Information Facility (NAIF) SPICE kernels providing the spacecraft ephemerides and camera attitudes as functions of time If these parameters are not known with sufficient accuracy, the derived products are systematically corrupted and can only be regarded as a first approximation to reality. A way to improve the a priori known parameters is a BA that rigorously models the geometric recording situation as realistically as possible and provides improved values for the interior and exterior orientation parameters
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