XVIIIth Congress: XVIIIth Congress

kraus, karl; waldhäusl, peter

Bibliographic data

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:: 1667437070

Title:: XVIIIth Congress

Scope:: 230 Seiten

Year of publication:: 1996

Place of publication:: Vienna

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

Identifier (digital):: 1667437070

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(31,B1)

Language:: English

Additional Notes:: Erscheinungsdatum des Originals ist anhand des Copyrightjahrs ermittelt.

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 Primary Data Acquisition

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 Primary Data Acquisition

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 Primary Data Acquisition

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 Primary Data Acquisition

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:: THE OPTIMIZATION OF THE STEREO ANGLE OF CCD-LINE-SCANNERS Anko Börner

Document type:: Multivolume work

Structure type:: Chapter

orward “nadir Fig. 6 Track of the border pixels of two different lines So it is getting more difficult for the match algorithm to identify points correctly. The probability of wrong match results increases. This is especially important for highly elliptical satellite orbits. Shading caused by the optical components of the system (cos*-law) influences the signal-to-noise ratio of the data. This ratio is not only determined by the field of view, but by the stereo angle as well. Consequently the bigger the stereo angle, the smaller the signal-to-noise ratio. And again it becomes more difficult for the match program, to find conjugated points. Besides there is still another point. The larger the stereo angle, the more it becomes probable that certain areas on the surface are invisible for a CCD-line. The last three effects plead for a small stereo angle. These counteracting processes are responsible for the for- mation and definition of an “optimal” stereo angle we want to find. 3. INVESTIGATIONS The value of this optimal value of the stereo angle was determined in dependence on the following parameters (Börner, A., 1995): - elevation dynamic of the observed terrain - ground resolution of the camera. 3.1. Influence of elevation dynamic Elevation dynamic in this contents means the standard deviation of the original elevations given as a grid of sam- ples. The distance of these samples should be equivalent to the ground resolution of the camera. In order to have comparable conditions one area of the Mars was selected. The existing terrain model was modi- fied in the following way: The DTM was compressed by factor 5 once and exagge- rated by factors 3,4 and 5. The simulated ground resolu- tion is about 1 km and resulted from 256 pixels per line, a field of view of 80 degrees and a flight height of 150 km. This value corresponds to the resolution of the original DTM of Mars (U.S. Geological Survey, 1992). For the evaluation of the results the following criterions were selected: - accuracy of single reconstructed points - number of matched points - accuracy of the whole reconstructed DTM. A measure for both accuracies is the standard deviation of the elevation errors. The results of the investigation are 28 shown in Fig. 7 to Fig. 9. In Fig. 7 the standard deviation of the elevation errors of all matched points is drawn in dependence on the exaggeration factor and the stereo angle. It could be established that up to a value of about 15 degrees for the stereo angle the determination of the elevation of single points is getting more accurate. After that there is no improvement of the results. So it makes no sense to make the stereo angle greater than this value. A stereo angle smaller than 10 degrees yields too large errors. The second curve shows the number of matched points in dependence on the stereo angle and the exaggeration fac- tor. The more the original DTM was exaggerated the less the number of conjugated points could be found. Also the number of matched points decreases with an increasing stereo angle. In the previous section was tried to explain the reasons for this effect. The exaggeration factor causes an increase of the local elevation dynamic. Since the used match algorithm evaluates the local image correlation, it is clear that a strong local elevation dynamic causes a rapid change of the local image correlation even for small changes of the viewing direction. An extreme example for such a kind of areas are urban terrains. The nadir line just sees the roofs and no walls, the other lines have a totally different impression. Even for flat areas the number of conjugated points decreases drastically for stereo angles greater than 40 degrees. Fig. 9 is the result of the two previous curves. It shows the standard deviation of elevation errors of the whole DTM, i.e. the interpolated points were taken into consideration. For all exaggeration factors a minimum of these curves exists. The bigger the factor the more the minimum becomes expressed. For flat areas the stereo angle doesn't play any important role. But for terrains with a big local elevation dynamic the range of permissible stereo angles gets smaller. The parts of the curves can be explained with the results shown in Fig. 7 and Fig. 8. Up to a value of about 15 degrees for the stereo angle the stan- dard deviation becomes smaller. After that the influence of the interpolation algorithms increases, because the number of conjugated points decreases. The large deviations of the measured values from the curves in the plots even for great exaggeration factors indi- cate an essential dependence of the results on the choice of the starting points of the matching algorithm. To sum up, there are permissible ranges of the stereo angle in dependence on the elevation dynamic of the observed area. But the application of an stereo angle between 15 and 20 degrees enables a sufficient accuracy in determining single point elevations as well as a suffi- cient number of conjugated points in two images. International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B1. Vienna 1996

Access restriction

Copyright

fullscreen: XVIIIth Congress (Part B1)

Multivolume work

Volume

Chapter

Table of contents

Cite and reuse

Volume

Chapter

Image

Image fragment

Citation links

Citation recommendation