NASA SRTM Global 3 Arc Second Number Files V003

NASA's Shuttle Radar Topography Mission (SRTM) generated a near-global digital elevation model from 80% of Earth's landmass between 60° N and 56° S. The mission flew aboard the Space Shuttle Endeavour for 11 days in February 2000, using radar interferometry from an altitude of 233 kilometers. This dataset provides ancillary 'number' files indicating the data source for each pixel in the corresponding 90-meter resolution elevation model.

Use Cases

• Assess pixel-level data source reliability based on the ancillary number values.
• Distinguish land from water pixels using the rule that numbers less than 6 indicate water and greater than 10 indicate land.
• Analyze the composition of the DEM by identifying pixels filled with ASTER GDEM or other sources.
• Combine the number files with the corresponding elevation product for quality-controlled terrain analysis.

Strengths

• Data voids from earlier versions have been filled using ASTER GDEM, GMTED2010, and NED sources.
• Covers 80% of Earth's total landmass, providing extensive spatial coverage.
• Ancillary files provide a clear numeric indicator (0-255) for the source of each DEM pixel.

Limitations

• Column-level documentation is absent; field semantics must be inferred after download.
• The 3 arc second data was derived from the 1 arc second data using sampling and averaging methods, which may affect local detail.

Provenance

Source

National Aeronautics and Space Administration (NASA) in collaboration with the National Geospatial-Intelligence Agency (NGA) and German and Italian space agencies.

Collection Method

Generated via radar interferometry from the SRTM payload on the Space Shuttle Endeavour (STS-99 mission).

Time Range

Data collected during the 11-day mission launched February 11, 2000.

Freshness

Last updated 2026-03-12 23:28:43.304080; freshness should be verified.

Geography

Near-global coverage of land between 60° N and 56° S latitude.