Practical testing and evaluating of the EOS PhotoModeler ®, an off-the-shelf digital close range photogrammetric software package
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In the current digital era, digital close range photogrammetry is finding more ways than ever for extracting geometrical information from the objects by photogrammetry, by merging with related technologies such as CAD, digital image processing, computer graphics and 3-D modeling. Digital close range photogrammetric software based on this and aiming at non-photogrammetric environments is consequently acquiring a fast increasing market. In this project, a successful low-cost digital close range photogrammetric software package PhotoModeler® Pro (PM Pro), developed by EOS Systems Inc. in Canada is evaluated. The evaluation is based on practical tests with related analysis and discussions, concerning the software’s photogrammetric performance with non-metric images, mainly in terms of accuracy, reliability and flexibility, as well as for a general outlook.
The practical testing was carried out with three different types of non-metric images and two different test fields. The images include scanned hard copy images and digital camera images taken with two different low-cost digital cameras. The two test fields include a small object, namely a 3-D metal plate, and a large object namely a wooden house. 3-D control points with high precision are uniformly distributed on both test fields. The preparations of the test fields are first briefly introduced, followed by the tests, analysis, discussions, conclusions and suggestions.
The evaluation was accomplish by testing and analyzing the results from different control configurations, different images, different objects and different adjustment options. The photogrammetric performance and outlook of PM Pro are generally promising according to the tests. Optimum strategies for applying PM Pro to the measurements of small and large objects with two different types of non-metric images are investigated and presented. The software’s requirements and limitations in control points, initial parameters and coordinate systems for processing non-metric images are given. The defects of Pm Pro found in tests, and their practical solutions or theoretical discussions are presented. Suggestions for further improvements of this software or other similar software are made, based on corresponding theoretical discussions. Some analysis and discussions are of general value in addition to the evaluation for this software, such as the suggestion of the photo-variant approach as the camera calibration scheme for non-metric cameras, the need of compensating for the systematic image errors caused by scanning and by digital image’s radiometric properties, and the suggestion and proof of the pseudo camera concept. Some issues worth of further investigations are suggested, including the reasons for which the accuracies from digital camera images are significantly higher than those from scanned hard copy images, and the merging of closer range photogrammetry with GIS.
PM Pro is a flexible tool of close range photogrammetric measurement in non-photogrammetric environments, while the knowledge of photogrammetry is still helpful for making full use of such software.
Keywords: digital, close range photogrammetry, software package, testing, evaluation.