An optimized data reduction technique in photogrammetry
Sayed, Sayed Heshmat
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https://hdl.handle.net/2142/21751
Description
Title
An optimized data reduction technique in photogrammetry
Author(s)
Sayed, Sayed Heshmat
Issue Date
1994
Doctoral Committee Chair(s)
Pecknold, David A.
Department of Study
Civil and Environmental Engineering
Discipline
Civil Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Civil
Language
eng
Abstract
The Direct Linear Transformation (DLT) method was first reported on in 1974 as an attractive alternative to existing photogrammetric reduction schemes for non-metric photography. While DLT resolved the problems of non-metric photography not having camera calibration information or fiducial marks for transformation of measured comparator coordinates to image coordinates, it was extremely limited in blunder detection capabilities and required an inordinately large number (six) of control points per photo for a solution.
Data snooping was introduced in the 1980's into the DLT for more efficient blunder detection. Unfortunately it required manual elimination of blunders, could not resolve multiple blunders, and was extremely ineffective in situations of a small number of control points or small number of photos. This thesis reports on the implementation of a robust blunder detection strategy within the DLT algorithm which has successfully resolved the shortcomings of data snooping and enabled automatic blunder removal.
The control point limit in DLT has been reduced to three for an entire job (from six per photo) through two improvements. The first was the incorporation of measured exposure station coordinates as additional observations. This development was precipitated by the successful inclusion of measured exposure station coordinates derived from the Global Positioning System (GPS) in aerotriangulation. The second strategy was the replacement of the conventional two step resection/intersection DLT solution with a simultaneous solution. These two additions have also provided much higher accuracies to be obtained by the DLT solution even when a minimum number of control points are utilized.
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