SRTM DEM

SRTM (Shuttle Radar Topography Mission) DEM is unique product which was produced by NASA and NGA in cooperation with German and Italian space agency.
In February 2000 special mission of Endeavour spaceshuttle started. The aim of this mission was to obtain elevation data on a near-global scale. Endeavour carried specially modified radar system which acquired interferometry data during an 11-day mission. Because of interferometry technique and frequencies used it was possible to acquire data disregarding daytime and meteorological conditions (more than 90 % of area was acquired twice and nearly 50 % three times). Processing of data resulted in most complete near-global high-resolution and high elevation accuracy database of the Earth.

There are two levels of SRTM DEM:

• SRTM1
  Available for USA with 1” spatial resolution (approx. 30 m on equator).

• SRTM3
  Available for area between 56 degrees south latitude and 60 degrees north latitude (covers 80 % of mainland) with 3” spatial resolution (approx. 90 m on equator)

SRTM DEM is distributed in the form of squares of size 1 degree latitude x 1 degree longitude (it represents the area of approx. 111 km x 111 km on equator).
SRTM DEM is available in two verisions. Version 1.0 includes altitudes as a result of interferometry processing. In version 2.0 some corrections in problematic regions (such as water bodies, coastal areas, local discontinuities, steep slopes, ...) are included.
Every SRTM3 version is available in two forms, which differs in resampling method (subsampling or averaging).

Basic characteristics:

Grid	Coordinate system	Accuracy		Data format
		Horizontal	Vertical
		CE90	LE90
3” (1”)	WGS84 / EGM96	20 m	16 m	HGT (16bit)

SRTM DEM is available free of charge via FTP or on CD/DVD (service charged). More info including download links can be found at USGS EROS Data Center.

GISAT offers SRTM DEM products fulfilling customer specific requirements – e.g. mosaicking tiles into larger areas, reprojections to desired coordinate systems, resampling into defined grid, etc.

In the Data download section SRTM DEM data for Czech Republic and Slovakia are available for download provided in both national coordinate systems: S-JTSK (Krovak, Bessel elipsoid) and S-42 (Gauss-Kruger, Krasovsky elipsoid).