XVIIIth Congress: XVIIIth Congress

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:: 1667438379

Title:: XVIIIth Congress

Scope:: 449 Seiten

Year of publication:: 1996

Place of publication:: Vienna

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

Identifier (digital):: 1667438379

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(31,B2)

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 Instrumentation for Data Reduction and Analysis

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 Instrumentation for Data Reduction and Analysis

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 Instrumentation for Data Reduction and Analysis

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 Instrumentation for Data Reduction and Analysis

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:: DYNAMIC WINDOW SIZE LEAST SQUARES MATCHING FOR AERIAL TRIANGULATION POINTS Shue-chia Wang, Sysh-Hong Chiu, Chi-Chang Tsai

Document type:: Multivolume work

Structure type:: Chapter

fthe It is | the tizer hing y by hing d by nine ned, | for tthe ding | the ut in stem ause man tem, arch yout can from nt of ke in !see TPs the icult. d be n of jonal from atch xels. ry to digitize the whole photograph and since the blind, fully automated system is not easy to develop, we decided to use this RS1 to develop a kind of semi-automatic TP measuring system. We call it the semi-automatic system, because the area which should be digitized is determined by the operator not by the computer. That is, conjugate areas in the overlapping photographs are searched by the human operator. Each time only a small area is digitized by the CCD camera. This area will be called the tie area, because in it the aerial triangulation tie points should locate. Since the conjugate tie areas in different photographs are selected and digitized by human operator, the difficult blind searching of them in the whole block or in a whole photograph is avoided. After these areas have been digitized, TPs will be defined in them and transferred between them. The methods used in our system for defining and matching the TPs are mainly adopted from the Helava's proposal for the DCCS. The greatest change in our system is that instead of using one fixed window size, we use several different sizes for the Least Squares Matching window in order to increase the reliability and the accuracy of the matched results. Another change is that we match each time only one pair of tie areas. There will be no multiple image matching like in the DCCS. With this semi-automatic point measuring system, we combine the point transfer and the point measurement in one procedure. Both the speed and the accuracy of the aerial triangulation point measurement are increased. Since only small tie areas are digitized, the data amount is very small. There is no problem concerning the storing and the managing of the image patches. An ordinary PC486 is used for this system. After the tie area is digitized, image pyramids will be built up. From all the conjugate tie areas, one will be chosen as the master tie area and the rests as slave tie areas. In the highest level (with the lowest resolution) of the pyramid of the master tie area image, the Foerstner interest operator is used to find the places where the windows for defining the TPs should be. A number of such places should be chosen, in case that some would fail in the Subsequent matching. These places will be traced down through the pyramid to the lowest level (with the highest resolution). The actual TPs will finally be found there. While applying the Least Squares Matching technique, we have noted that the reliability is a problem. If the initial approximate position for starting the matching is not accurate enough, the LSM method could converge to a false place and there is no information from the matching itself to judge the reliability. Also the size of the matching window is a problem. There is no such thing as the best window size. Different window sizes converge to different positions, the difference can some times be larger than 0.2 397 pixel. Therefore we have developed a strategy to cope with these problems. Instead of one fixed window size, we use several different sizes for the LSM and by analyzing their normalized cross correlation coefficients (NCC) after the LSM matching, the best result is selected. When no reliable one could be found, that point will be abandoned. If there are not enough reliable points in a tie area, the system will switch automatically to the manual selection of the target and the search windows in the master and the slave tie areas respectively. 2. System Configuration The whole system is built up on the basis of the Rollei RS1 scanner running on a COMPAQUE PC. The RS1 is designed for digitizing the photographic film with very high geometric accuracy at low costs. Which is achieved by using a reseau plate (Luhmann and Wester-Ebbinhaus 1986). The main parts ofthe RS1 area CCD camera anda glass picture carrier with 2mm spacing reseau crosses all over its entire surface. The CCD camera has an array of 512x512 pixels and locates above the picture carrier. The pixel size in the film is approximately 8umx 6um. Therefore the total area of the film which can be digitized at one time is approximately only 4mm x 3mm. But the CCD camera can be moved to any place over the picture carrier by step motors, so that the whole picture can be digitized patch- wise. Since step motor is not very accurate, Luhmann and Wester-Ebbinhaus developed this cheap solution of using. reseau plate to obtain the high precision absolute reseau coordinates for each pixel. Two different light sources are built in the RS1 which can be Switched automatically in turn. When the bottom light is switched on, the light goes through the film into the CCD, and the film can be digitized. When the side light is switched on, only the reseau crosses are imaged into the CCD. In this case, the pixel coordinates of the reseau cross center can be obtained after an automatic matching of the cross image to the standard template. Then the transformation parameters from the pixel coordinates to the reseau coordinates can be calculated. Since the absolute coordinates of the reseau crosses are known, the absolute coordinates of each pixel can be calculated by the transformation parameters. The distance between the reseau crosses is 2mm and the CCD digitizes an area of 4mm x 3mm, so that it is guaranteed that there will always be at least 4 reseau crosses used for calculating the transformation parameters. The area encompassed by the 4 crosses has approximately 240x350 pixels. In order to reduce the error caused by extrapolation, only the pixels within the four crosses will be used for the TP measurement. The CCD camera can be driven by the reseau coordinates or by the photo coordinates. In our case we drive the CCD International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996

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