Displacement monitoring by integrating on-line photogrammetric observations with dynamic information
Data collection and – processing in photogrammetric monitoring are thoroughly investigated. The determination of displacements by photogrammetry requires multiple photographic campaigns and therefore photo-measurements on multi-temporal photographs. An on-line semi-automatic photogrammetric system for targeted and natural object points using the analytical stereo-plotter has been developed. In the case of targeted points, the analytical plotter has been utilized as an on-line mono-comparator with the measuring mark driven automatically to predetermined photo-locations. For natural points an integrated “cross-identification” and measuring procedure has been designed and implemented. The combination of comparator/stereo-plotter mode allows the point-transfer operation to be done “digitally”. In both cases image positioning is performed under computer control, and on-line editing capabilities are provided. A combined sequential photogrammetric approach was developed for data processing. The dynamic characteristics of the object position vectors are introduced in both the functional and stochastic models. This, the single epoch static photogrammetric model has been extended to incorporate the additional object information where the object parameter vector is updated not only as new observations become available but also as a function of time. Examples with real and simulated data are given which demonstrate the usefulness of the newly developed methodologies. That is, a) the time required for the photo-measurements is significantly reduced while their accuracy is improved, and b) the integration of photogrammetric and dynamic information provides better estimation or the location and accuracy of the unknown parameters.