NASADEM Merged DEM Global 1 arc second

PI: Sean Buckley


The Land Processes Distributed Active Archive Center (LP DAAC) is responsible for the archive and distribution of the NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) Digital Elevation Model (DEM) version 1 (NASADEM_HGT) dataset, which provides global 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_HGT data product layers include DEM, number of scenes (NUM), and an updated SRTM water body dataset (water mask). The NUM layer indicates the number of scenes that were processed for each pixel and the source of the data. A low-resolution browse image showing elevation is also available for each NASADEM_HGT granule.

The global 1 arc second NASADEM product is also available in NetCDF4 format as the NASADEM_NC dataset with the source of each elevation pixel in the corresponding NASADEM_NUMNC product.

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Collection and Granule


Characteristic Description
File Size~.78 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 FormatHGT or netCDF-4
Geographic Dimensions1 degree lat x 1 degree lon


Characteristic Description
Number of Science Dataset (SDS) Layers3
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
DEM Void-filled DEM Meters 16-bit signed integer N/A N/A -32767 to 32767 N/A
NUM¹ Number of scenes Class 8-bit unsigned integer N/A N/A 0 to 255 N/A
SWB Updated SRTM water body data Class 8-bit unsigned integer N/A N/A 0, 255 N/A

¹The contents of the NUM file indicate number of DEM tiles used and the source of the data.

Reference Data for Number of Scenes Layer

Value Description
0 Water in corrected SRTM water body data
1-23 SRTM 1 to 23 (max known is 23)
41-94 PRISM 1 to 50 (54 max polar, 37 max elsewhere)
110-160 GDEM3 (saturated at 50)
170-220 GDEM2 (saturated at 50)
231 SRTM V3 from GDEM3
232 SRTM V2 from GDEM3
233 SRTM V2 from GDEM2
241 NED from GDEM2 (USA)
242 NED from GDEM3 (USA)
243 CDED from GDEM2 (Canada)
244 CDED from GDEM3 (Canada)
245 Alaska DEM from GDEM2 (Alaska)
246 Alaska DEM from GDEM3 (Alaska)
250 Interpolation
251 Quad edge averaged where two neighboring quads disagreed (generally a GDEM error)
255 ERROR (if NUM IS MISSING - none known to exist)

List of abbreviations: PRISM = Advanced Land Observing Satellite (ALOS) Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM), NED = U.S. Geological Survey (USGS) National Elevation Dataset, CDED = Canadian Digital Elevation Data, Alaska DEM = USGS 3D Elevation Program (3DEP) Alaska DEM

About the image

NASADEM 1 arc second elevation data over the Grand Canyon, 2000.

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User Guide
Shuttle Radar Topography Mission (JPL) Webpage
DEM Comparison Guide

Using the Data

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