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Authors: Bradley, James
Keywords: Computer Science
Issue Date: 1-Dec-1997
Abstract: This paper discusses a modularized design for a Mars Global Terrain Database. The design provides for elevation data with respect to a triaxial ellipsoidal reference datum developed for Mars by USGS. Terrain data is recorded for 1-second of arc grid elements over the surface of Mars. A 400 Gigabyte column-gridded relation called Terrain contains the surface terrain data. Data for Terrain is expected in 1999-2000 from the Mars Global Surveyor satellite currently in initial polar orbit around Mars. Each tuple of Terrain contains data for a N-S column-grid of 900 1-second grid elements. There is thus a set of tuples per 1-degree rectangle, with the number of tuples per set decreasing with the cosine of latitude. Surface resolution is a uniform 16.5 meters everywhere with a 1-second grid. The design constrains tuple sizes in Terrain to permit efficient blocking and manipulation of the records of the underlying storage file. Terrain contains a virtual-attribute function for geodetic computations relating to the triaxial ellipsoidal reference datum. The database also relates Mars feature-type relations to Terrain. Terrain's gridded structure is transparent to users writing SQL expressions to retrieve Terrain data on the basis of specific features. Many different distinct feature-type relations can be included. At least two of these are participate in recursive relationships. The design also allows attachment of additional feature-type relations in a modular manner, correctly related to Terrain, without affecting the contents of Terrain.
Appears in Collections:Bradley, James

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