System Calibration, Geometric Accuracy Testing and Validation of DEM and Orthoimage Data Extracted From Spot Stereo-Pairs Using Commercially Available Image Processing Systems

Al-Rousan, Naief Mahmoud (1998) System Calibration, Geometric Accuracy Testing and Validation of DEM and Orthoimage Data Extracted From Spot Stereo-Pairs Using Commercially Available Image Processing Systems. PhD thesis, University of Glasgow.

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This thesis covers the system calibration and the geometric accuracy testing and validation of the data produced by the photogrammetric modules of a number of digital image processing systems that have been developed recently to produce DEMs and orthoimages from SPOT IB stereo-pairs. This work has been carried out over a high accuracy test field that has been established in the Badia, a desert area in North East Jordan. The reference data comprises 130 points whose positions and elevations have been established using high precision GPS sets, supplemented by digitized contours from existing maps and elevation profiles measured using kinematic GPS techniques. After a initial review of previous research work in this area, the mathematical modelling and the analytical photogrammetric solutions used by the tested systems are discussed at some length, including the algorithm employed in the automatic image matching procedures used to extract a dense DEM from the SPOT digital images. The results of extensive tests of the geometric accuracy of planimetry and height obtained by these systems and the many problems encountered with these systems are reported in detail, as are the solutions that have been devised in collaboration with the system suppliers to overcome these problems - to the benefit of the whole mapping community. The results from tests of the planimetric accuracy obtained from the modified 3-D systems show a sub-pixel accuracy and correspond to the accuracy specifications of 1:50,000 scale topographic mapping. In the case of the height accuracy, the results obtained at both the control points and check points mostly lie in the range between +/- 5 to 8m and show that it is now possible with digital systems to reach accuracies comparable with those previously achieved with analytical plotters. On completion of the accuracy tests using the ground control points, DEMs of the test area were generated by each of the systems from the SPOT Level 1A and IB stereo- pairs using automatic matching techniques. These DEMs have then been merged and validated. Four different methods of validation have been applied to test the accuracy of the elevation data in the DEMs using the reference contour and profile data sets. The results of the extensive series of height accuracy tests correspond to the requirements of contouring at 20 to 30m interval which may meet the specifications of 1:50,000 scale topographic maps in certain areas but more often those at smaller scales. The final orthoimages produced by these systems are of a high quality in radiometric terms, while a check of their geometric accuracy reveals sub-pixel accuracy with planimetric accuracy varying slightly from one system to another. The geometric accuracy tests and the validation of the DEMs carried out in the present research have been analyzed and compared with the geometric accuracy tests and validations of the DEMs reported by several previous researchers over different test areas. These comparison show that the results obtained in the tests carried out over the Badia test field are among the best that have been achieved using digital photogrammetric systems and indeed are superior to most of the accuracy tests reported by other researchers. After the systems had been modified as a result of the author's work, the results of this highly automated all-digital photogrammetric procedure are of especial relevance to those concerned with the topographic mapping of extensive areas of arid and semi-arid terrain. The test field with its network of high accuracy ground control points and its reference data sets has shown its worth and is available and suitable for the calibration and testing of the images from the forthcoming high- resolution Earth Observation satellites.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: G Petrie
Keywords: Remote sensing, Geographic information science and geodesy
Date of Award: 1998
Depositing User: Enlighten Team
Unique ID: glathesis:1998-75399
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 20:16
Last Modified: 19 Nov 2019 20:16

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