XVIIIth Congress: Commission VI

Kraus, Karl; Waldhäusl, Peter

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Multivolume work

Persistent identifier:: 1667435949

Title:: XVIIIth Congress

Sub title:: Vienna, Austria 1996

Year of publication:: 1996

Place of publication:: Vienna

Publisher of the original:: Austrian Society of Surveying and Geoinformation

Identifier (digital):: 1667435949

Language:: English

Editor:: Kraus, Karl; Waldhäusl, Peter

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing

Document type:: Multivolume work

Volume

Persistent identifier:: 1677550198

Title:: Commission VI

Scope:: 149, 110, 92 Seiten

Year of publication:: 1996

Place of publication:: Vienna

Publisher of the original:: Austrian Society of Surveying and Geoinformation

Identifier (digital):: 1677550198

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(31,B6)

Language:: English

Additional Notes:: Die Vorlage enthält insgesamt 3 Werke: Commission VI (Seiten 1-149); National reports (Seiten 1-110); Special sessions (Seiten 1-92)

Other Title:: Enthaltendes Werk: National Reports; Enthaltendes Werk: Special sessions

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Kraus, Karl; Waldhäusl, Peter

Corporations:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Economic, Professional, and Educational Aspects of Photogrammetry and Remote Sensing

Adapter:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Economic, Professional, and Educational Aspects of Photogrammetry and Remote Sensing

Founder of work:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Economic, Professional, and Educational Aspects of Photogrammetry and Remote Sensing

Other corporate:: International Society for Photogrammetry and Remote Sensing, Congress, 18., 1996, Wien; International Society for Photogrammetry and Remote Sensing; International Society for Photogrammetry and Remote Sensing, Commission Economic, Professional, and Educational Aspects of Photogrammetry and Remote Sensing

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2019

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: Special Session

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: EXPERIMENTAL TESTS ON FAST AMBIGUITY SOLUTIONS FOR AIRBORNE KINEMATIC GPS POSITIONING. Prof. em. Friedrich Ackermann [...] ISPRS Commission II

Document type:: Multivolume work

Structure type:: Chapter

EXPERIMENTAL TESTS ON FAST AMBIGUITY SOLUTIONS FOR AIRBORNE KINEMATIC GPS POSITIONING Prof. em. Friedrich Ackermann Institute of Photogrammetry University of Stuttgart Keplerstr. 11, 70174 Stuttgart Germany ISPRS Commission II KEY WORDS: Kinematic GPS, ambiguity solutions. ABSTRACT OEEPE has started experimental investigations into the accuracy and reliability of fast OTF ambiguity solutions, based on controlled test flights in Norway and Germany. The paper reports about first results of the testflight Vaihingen by the pilot centre Stuttgart. Ambiguity solutions were successfully obtained up to distances of 386 km to the GPS ground stations, although the restored trajectories after signal interruption show small discontinuities and biases. The comparison with check values at camera air stations (by aerial triangulation) showed no accuracy dependency on distance to ground station (with one exception in z), but confirmed sytematic errors. The results are preliminary, awaiting completion of the additional tests. 1. INTRODUCTION 1.1 Biased ambiguity solutions High precision airborne kinematic GPS positioning by differential phase observations has been applied in photogrammetry for several years. A particularly successful field of application has been GPS camera positioning for aerial triangulation, by which ground control points could be greatly reduced. The main problem has been, from the beginning, the question of obtaining continuous and absolute GPS flight trajectories. There has always been the risk of signal interruption during flying, especially during flight turns. Such interruptions had to be accepted as real, not being completely and safely avoidable. Software methods for re- establishing ambiguity solutions were not available, for a long time. The only accessible practical approach was, therefore, to re-solve for ambiguities, after interruption, on the basis of the less precise C/A code pseudo-range positioning. The resulting ambiguity solutions were biased, in this case, and there remained discontinuities in the GPS trajectories. And, the subsequent parts of a GPS trajectory showed systematic (drift) errors which, fortunately, remained approximately linear for some short time afterwards. Such potential (constant and linear) GPS drift errors could be described by linear correction terms which - in the case of aerial triangulation - were applied and solved for during the combined block adjustment. That approach represented a most successful engineering solution to the problem and has worked very well in practice. There was, however, one condition attached: In order to avoid singularities in the block solution some additional GPS controlled cross-strips had to be flown and used in the combined block adjustment. For general reasons the drift parameters were usually applied per strip. Also, it became customary, to rely on a few ground control points, for solving the datum problem. The method of linear GPS corrections implied that any additional constant or linear errors were compensated as well. That method has worked very well. It is accurate, reliable, safe. Many aerial triangulation projects have been treated in this way, without any problems. It is a special advantage, too, of the method 1 that the ground receiver station can be placed at great distance from the mission area, up to 500 km or more, which sometimes is highly essential. Also the conventional single frequency GPS receivers were applicable. Recent additional developments (2 GPS antennae on the aircraft, more than 1 ground receiver station) have made the system safer, but are not considered mandatory. It can be summarized that the approximate resp. biased ambiguity solutions of the method are unable to provide absolute GPS positions nor continuous trajectories. The post-solution via combined block adjustment is restricted to GPS application for aerial triangulation, i.e. in combination with aerial photo coverage. Other sensors (e.g. laser scanner) rely, however, on absolute GPS positioning. Hence, that method could and can only be considered an intermediate solution, awaiting more sophisticated techniques for fast ambiguity solutions, also known as OTF (on the fly) methods. 1.2 Fast OTF ambiguity solutions The recent development of GPS hardware and software has changed the situation. Fast OTF solutions have been developed, based on dual frequency receivers. They are to provide continuous GPS trajectories by correctly restoring the ambiguity solutions after signal interruption. Successful applications have been reported. The method has started to be applied in practice. Only, the reliability of the method has remained unclear. Seemingly, the method does not always give successful solutions if the distance between roving and stationary GPS receivers is large. It is understood, more or less, to remain within a distances of 50 km, preferably 30 km, in order to be safe. Also, it is not really known on what effects the reliability might depend. Practical application can accomodate to such restrictions, in many cases. Nevertheless, larger ranges would be highly desirable. 1.3 Experimental tests by OEEPE In that problem situation the European Organisation for experimental photogrammetric research (OEEPE) decided to take up experimental International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B6. Vienna 1996

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