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C. Ressl, N. Pfeifer, G. Mandlburger:
"Applying 3D Affine Transformation And Least Squares Matching For Airborne Laser Scanning Strips Adjustment Without Gnss/imu Trajectory Data";
Talk: ISPRS Workshop Laser Scanning 2011, Calgary, Canada; 2011-08-29 - 2011-08-31; in: "Proceedings", ISPRS, Xxxviii / 5 / W12 (2011), ISSN: 1682-1777; 6 pages.

In this article we extend our previous work on the topic of ALS strip adjustment without GNSS/IMU trajectory data. Between overlapping
strip pairs the relative orientation as a 3D affine transformation is estimated by a 3D LSM approach, which uses interpolated 2.5D
grid surface models of the strips and the entire strip overlap as one big LSM window. The LSM derived relative orientations of all strip
pairs in the block together with their covariance matrices are then used simultaneously as observations in an adjustment following the
Gauss-Helmert model. This way the exterior orientation of each strip is computed, which refers to a relative block system. If proper
ground control data is given, then an absolute orientation of the block of strips can be computed by a final LSM run. In a small example
consisting of 4 strips with ca. 70% overlap the improvement in the relative geometric accuracy is demonstrated by the decreasing
sigmaMAD of the height differences from 8:4cm (before) to 1:6cm (after the strip adjustment).

http://publik.tuwien.ac.at/files/PubDat_199912.pdf