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30 July 1998 Controlled digital elevation data decimation for flight applications
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In future aircraft cockpit designs SVS databases will be used to display 3D physical and virtual information to pilots. One of the key elements is reliable display of terrain elevation data in order to increase situation awareness. Displayed data and the outside world must match concerning position and altitude. Therefore, terrain elevation data with specified error values are required to guarantee reliability and integrity. The determination of the database error imposes two major steps. The first step applies to the generation of the primary database. Today several companies start to provide elevation models generated by different methods taken from independent sources. If not stated, the error of these databases has to be calculated and verified by the use of reference data and statistical methods. Some commonly used models (like DTED) were investigated, errors estimated, and compared. The second step is required for the preparation of data to be used in a SVS. For most of today's graphics machines the amount of data is too large to be drawn at an acceptable frame rate. Therefore, polygonal decimation is used to reduce the number of triangles to be rendered. Most algorithms used for decimation were developed for the visual quality of the decimated terrain. Their parameters do not allow to perform an error bounded decimation because they are based on criterion like 'face angle' or 'bounding box size.' However, it is necessary to know the absolute error introduced by the decimation for an SVS. An algorithm was developed to eliminate vertices only if the newly introduced error is smaller than a given threshold. In addition, this algorithm tries to preserve important features such as ridgelines. Knowing the maximal altitude error of a certain position and the error introduced by decimation, it is possible to generate a worst case elevation error for that point.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ludwig May, Jens Schiefele, and Helmut Raabe "Controlled digital elevation data decimation for flight applications", Proc. SPIE 3364, Enhanced and Synthetic Vision 1998, (30 July 1998);


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