NASADEM SRTM Subswath Global 1 arc second

PI: Sean Buckley


The Land Processes Distributed Active Archive Center (LP DAAC) is responsible for the archive and distribution of NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Digital Elevation Model (DEM) version 1 (NASADEM_SSP) dataset, which provides global Shuttle Radar Topography Mission (SRTM) sub-swath elevation data at 1 arc second spacing.

NASADEM data products were derived from original telemetry data from the Shuttle Radar Topography Mission (SRTM), a collaboration between NASA and the National Geospatial-Intelligence Agency (NGA), as well as participation from the German and Italian space agencies. SRTM’s primary focus was to generate a near-global DEM of the Earth using radar interferometry. It was a primary component of the payload on space shuttle Endeavour during its STS-99 mission, which was launched on February 11, 2000, and flew for 11 days.

In addition to Terra Advanced Spaceborne Thermal and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) Version 2 data, NASADEM also relied on Ice, Cloud, and Land Elevation Satellite (ICESat) Geoscience Laser Altimeter System (GLAS) ground control points of its lidar shots to improve surface elevation measurements that led to improved geolocation accuracy. Other reprocessing improvements include the conversion to geoid reference and the use of GDEMs and Advanced Land Observing Satellite Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) AW3D30 DEM, and interpolation for void filling.

NASADEM are distributed in 1 degree latitude by 1 degree longitude tiles and consist of all land between 60° N and 56° S latitude. This accounts for about 80% of Earth’s total landmass.

NASADEM_SSP data product layers include radar total correlation, radar volumetric correlation, radar individual images, radar incidence angle (relative to ellipsoid), and radar incidence angle (local). A low-resolution browse image showing sub-swath elevation is also available for each NASADEM_SSP granule.

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Collection and Granule


Characteristic Description
File Size~30.9 MB
Temporal ResolutionMulti-Day
Temporal Extent2000-02-11 to 2000-02-21
Spatial ExtentGlobal (60°N to 56°S, 180°W to 180°E)
Coordinate SystemGeographic Latitude and Longitude
File FormatRAW
Geographic Dimensions1 degree lat x 1 degree lon


Characteristic Description
Number of Science Dataset (SDS) Layers5
Columns/Rows3601 x 3601
Pixel Size~30 m

Layers / Variables

SDS Name Description Units Data Type Fill Value No Data Value Valid Range Scale Factor
TOT_COR Radar total correlation N/A 16-bit unsigned integer 0 N/A Non-negative 0.0001
VOL_COR Radar volumetric correlation N/A 16-bit unsigned integer 0 N/A Non-negative 0.0001
IMG Radar individual images (10 * log10(actual value) + 128) Number 8-bit unsigned integer 0 N/A N/A N/A
INC0 Radar incidence angle relative to ellipsoid Degree 16-bit unsigned integer 0 N/A Non-negative 0.01
INC Radar incidence angle local Degree 16-bit unsigned integer 0 N/A Non-negative 0.01

About the image

NASADEM 1 SRTM Subswath data over the Grand Canyon, 2000.

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User Guide
Shuttle Radar Topography Mission (JPL) Webpage

Using the Data

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