The Use of Photogrammetry in the Measurement of the Deformation of a Box Girder Bridge.
Doctoral thesis, University of London.
A comprehensive series of calibrations of a Galileo- Santoni Special "A" stereometric camera pair was carried out in preparation for the structural deformation measurement of a model box girder bridge. The calibrations are described here. A qoniometer was built for the infinite focus calibration which in turn was required as a basis for comparison of the close focus calibrations. A new method of calibrating the cameras at less than 4m object distance was then devised, which proved capable of very high precision. It forms the only truly original part of this work. Results of all the calibrations were then examined and an unexpected change in principal distance was found at the close focus. The change is shown to be dependent on the positions of the entrance and exit pupils. The opportunity is taken to explain an effect known as the variation of principal distance with object distance, and to show that this variation is, in fact, non-existent. A simulation of the structural project was created in the laboratory and photographed. The photogranmetric results were obtained first using the maker's value of the principal distance, then using the principal distance derived from the infinite focus calibration and finally from the values obtained in the actual close focus calibration. The three results demonstrate the increase in accuracy obtained by calibration, and also the importance of the lens effect described above. Details are given of the photogrammetric process used on the box girder bridge. Finally, a critical appraisal is made of the use of photogrammetry in a project such as this.
|Title:||The Use of Photogrammetry in the Measurement of the Deformation of a Box Girder Bridge.|
|Open access status:||An open access version is available from UCL Discovery|
|Additional information:||Thesis digitised by British Library EThOS|
|UCL classification:||UCL > School of BEAMS > Faculty of Engineering Science > Civil, Environmental and Geomatic Engineering|
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