Final Tile Design Study for the Digital Chart of the World
Final study rept. Jul-Nov 1990
ENVIRONMENTAL SYSTEMS RESEARCH INST INC REDLANDS CA CENT
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Data density varies greatly from one ONC sheet to another, and since the ONCs are the source for the database, it is important to consider this variation in selecting a tiling method for the DCW. Because of its ability to effectively manage large variations in data density, an adaptive, rather than a fixed, tiling scheme was believed to be the best candidate at first. It was believed that a performance improvement could be obtained through the use of regular, systematic quadtree partitions. However, as the DCW evolved through a series of prototypes it became clear that the value of managing variations in density would have to be weighed against the disadvantages of any adaptive tiling scheme for other aspects of the DCW project, particularly production. By the time Prototype 3 was released, the recommendation for the tiling scheme had shifted from adaptive to fixed. The reason for the shift was explained at the Project Detail Design Review in August. By that time the effects of adaptive tiling on the project were understood well enough for adaptive tiling to be judged incompatible with the DCW. The recommendation was therefore made for the tiling to be fixed, and, further, for the fixed tiling to be regular. The recommended size of the fixed tile will be empirically determined after other, maturing elements of Prototype 4 can be evaluated.
- Cartography and Aerial Photography
- Computer Programming and Software