- DTED
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DTED (or Digital Terrain Elevation Data) is a standard of digital datasets which consists of a matrix of terrain elevation values. This standard was originally developed in the 1970s to support aircraft radar simulation and prediction.
DTED supports many applications, including line-of-sight analyses, terrain profiling, 3-D terrain visualization, mission planning/rehearsal, and modeling and simulation. DTED is a standard National Geospatial-Intelligence Agency (NGA) product that provides medium resolution, quantitative data in a digital format for military system applications that require terrain elevation.
The DTED format for level 0, 1 and 2 is described in U.S. Military Specification Digital Terrain Elevation Data (DTED) MIL-PRF-89020B, and amongst other parameters describes the resolution for each level:
- Level 0 has a post spacing of ca. 900 meters.
- Level 1 has a post spacing of ca. 90 meters.
- Level 2 has a post spacing of ca. 30 meters.
The precise spacing is defined by dividing the world into zones based on latitude, and is given in the following tables:
Zone latitude I 0°–50° (North–South) II 50°–70° (North–South) III 70°–75° (North–South) IV 75°–80° (North–South) V 80°–90° (North–South) level 0 (arc secs) level 1 (arc secs) level 2 (arc secs) latitude spacing 30 3 1 zone I longitude spacing 30 3 1 zone II longitude spacing 60 6 2 zone III longitude spacing 90 9 3 zone IV longitude spacing 120 12 4 zone V longitude spacing 180 18 6 In addition three more levels (3, 4 and 5) at increasing resolution have been proposed, but not yet standardized.
DTED data is stored in a big endian format where negative numbers are signed magnitude.
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