|M.Sc Student||Tilles Eli|
|Subject||Precise 3D Mapping by Close-Range Photogrammetry|
Supported Laser Scanning
|Department||Department of Civil and Environmental Engineering||Supervisor||Assistant Professor Uzi Ethrog|
In the last decade aerial laser scanning became the main technique for creating large scales digital photogrammetric models and GIS environments. The tremendous progress in this field improved terrestrial laser scanning as well, and today more and more projects utilize this technology. Terrestrial laser scanning has several distinct advantages: high speed collection and processing of data, accessibility to all objects in the field, high mobility and minimum manpower needed. The advantages of this method make it the tool of choice in unique situations.
This research deals with characterizing an optimal platform for terrestrial outlines. The platform is composed of a laser scanner, a differential GPS system for position acquiring, and a camera for orientation acquiring. All of these are synchronized and fixed together. This platform will offer a cheap and quick data collecting system.
The innovation and heart of this research is an algorithm that uses differential GPS-supported close range photogrammetry for solving the exterior orientation of the laser scanner. The datum defect in a photogrammetric system includes seven parameters, three components of translation, three of rotation, and one of scale. GPS measurements of the exposure station can fulfill a complete datum if at least three exposure stations are not co-linear. A solution to the geometric sensitivity of the algorithm is proposed too.
Three real experiments took place in the laboratory and in the field, in order to examine the theory in a real situation. During these experiments, the platform was calibrated, the accuracy estimation from this stage was crosschecked, and the ability of merging several scans into one model was tested. Comparing the results of the mapping and the decrease in mapping time with the results from traditional terrestrial methods, are illustrate the great potential of this method.