This raster grid datalayer consists of global 30 arc-second resolution elevation data derived from SRTM30 (Shuttle Radar Topography Mission) data, supplemented with GTOPO30 elevation data, ETOPO2 depth data, and other data sources. Elevation values are represented in meters above or below mean sea level.
The datalayer was produced by ISciences and published in 2003 as part of the TerraViva! SRTM30 global enhanced : elevation, slope and aspect, data set. SRTM30 data was collected February 11-22, 2000.
From the ISciences Web site:
"SRTM30 Enhanced Global Map is a global elevation and depth data set from ISciences at 30 arc-second resolution that includes an elevation map, slope angle map, slope aspect map, and source map. Each pixel represents an area ranging from one sixth of a square mile at 60 degrees to one third of a square mile at the equator. To get a view of your world as good as this you'd need a map 18 feet high and 36 feet wide! SRTM30 Enhanced Global Map was created by combining 27 SRTM30 elevation files, identifying and correcting anomalies, supplementing with elevation data from an alternate source for land areas not included in SRTM30, and adding depth data. The result -- a beautifully blended, high-quality, stunning global elevation and depth map suitable for display at scales to