A photogrammetric monitoring method of structural deformation has been developed during the course of this project.
The Gabion Wall, which is part of the I-90 project, has been used as the site for practical tests of the theoretical development. The monitoring consists of photographing the structure from three camera stations with KA-2 f=24" camera. The camera has been modified to a plate camera to provide the maximum accuracy.
The methodology consists of the geodetic determination of the camera location and the orientation and photogrammetric determination of targets (natural and artificial) on the structure. During the course of this project, more than 100 target locations were determined by three dimensional coordinates. The maximum error was found to be plus or minus 3/4 inch; the average, 1/2 inch. This represents a relative accuracy of from 1/58,000 to 1/120,000 of the photographic distance.
Using the actual construction site for research has permitted immediate implementation. The instrumentation as well as the methodology along with the computer program has been transmitted to the Washington State Highway Department and their Photogrammetric Branch has been assisted in the implementation.