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Citation |
Ballantyne JD, Dean DRJ, Thompson BL. Transp. Res. Rec. 1987; 1119: 47-54. |
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Copyright |
(Copyright © 1987, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing) |
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DOI |
unavailable |
PMID |
unavailable |
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Abstract |
The methods of analytical photogrammetry and microcomputer technology are combined to generate contour maps or cross sections, or both, of landslides along roadways with minimal conventional surveying. A conventional 35-mm camera and 8-in. by 10-in. photographs are used for the mapping. A minimum of two overlapping photographs are needed of the area to be mapped. Also, a minimum of six well-distributed control points are needed. Control points are points for which position (X and Y coordinate pair) and elevation (Z) must be obtained by conventional surveying techniques. The photogrammetric model used is the direct linear transformation model. This model uses x and y coordinates of corresponding images on two or more photographs to determine the position and elevation of such images in a ground-based coordinate system. A microcomputer performs the calculations and an electronic digitizer connected to the microcomputer is used to obtain the image coordinates on the photograph. The ouput can be in the form of a coordinate list of desired points, cross sections, a contour map, or three-dimensional perspective plot. The graphics are generated by a pen plotter connected to the microcomputer. Studies indicate that the error vector at about 400 ft is 0.4 ft for this system of mapping. A slope in distress can be monitored over a period of time. To eliminate resurvey, the six control points have to be located in a stable area. Language: en |
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Keywords |
LANDSLIDES; MAPS AND MAPPING; PHOTOGRAMMETRY - Cameras; SURVEYING - Computer Applications |