NASA SRTM: Global Shuttle Radar Topography Mission Elevation Data for GIS
NASA SRTM, the Shuttle Radar Topography Mission, is a foundational digital elevation dataset created from radar interferometry during the Space Shuttle Endeavour mission in February 2000. The dataset provides elevation measurements for most land between approximately 60° north and 54° south latitude, with widely used global products at 1 arc-second, approximately 30 meters, and 3 arc-seconds, approximately 90 meters. SRTM is distributed through NASA Earthdata, the NASA Land Processes Distributed Active Archive Center, and USGS EarthExplorer in formats including HGT, GeoTIFF, BIL, and DTED. It remains useful for terrain visualization, slope and aspect calculations, watershed modeling, drainage analysis, visibility studies, orthorectification, and geographic queries that depend on elevation. However, it is an historical elevation surface acquired in 2000, not a current terrain-monitoring system, a precise bare-earth model, or a universal substitute for local high-resolution elevation data.
NASA SRTM is one of the most widely used elevation datasets in the GIS and Earth-observation ecosystem. Its importance comes from combining broad geographic coverage, consistent production, relatively fine global resolution, and straightforward raster workflows. SRTM gives analysts a common elevation surface for comparing terrain across regions where national mapping agencies may publish data at different resolutions, with different vertical references, or not at all. The data is particularly valuable when a project needs to understand the shape of the physical world—mountain slopes, valley floors, drainage divides, elevation gradients, and terrain exposure—before combining those measurements with roads, buildings, waterways, infrastructure, land cover, or administrative areas.
How EDK fits
For: GIS analysts, remote-sensing practitioners, cartographers, hydrologists, environmental researchers, transportation and infrastructure teams, disaster-risk analysts, and developers building geographic applications that need a consistent elevation layer.
SRTM is a clear example of the elevation foundation required to find, understand, and compute about the physical world. On its own, SRTM is a raster surface: it does not identify every road, building, stream, or address. Its value increases when elevation is connected to geographic features and places. A world model can use SRTM-derived terrain measures to interpret whether a road climbs a steep slope, whether buildings lie within a low-lying basin, how infrastructure relates to ridgelines or drainage areas, or how accessibility changes across a region. The important connection is computational rather than promotional: SRTM supplies terrain evidence that can be joined, summarized, compared, and queried alongside other physical-world data. Analysts should preserve the dataset’s acquisition date, resolution, coverage limits, vertical conventions, and void-filling history when incorporating it into broader geographic reasoning.
- •Combine SRTM elevation with roads, buildings, waterways, and infrastructure to calculate terrain context such as slope exposure, elevation bands, proximity to ridgelines, or potential drainage direction. The result is a richer physical-world representation than either the elevation raster or feature layer provides alone.
- •Use SRTM as a common terrain baseline when ranking or comparing places across large regions—for example, identifying settlements in steep terrain, screening infrastructure corridors by elevation variability, or aggregating elevation statistics within administrative, ecological, or service areas.
- •Support geographic search and computation by attaching terrain-derived attributes to physical features, such as the mean elevation of a road segment, the maximum slope near a facility, or the elevation distribution of buildings within a watershed. These derived values should be treated as analysis results, not as attributes directly supplied by NASA SRTM.
Dataset profile
Formats
HGT elevation tiles, commonly distributed in compressed archives
GeoTIFF
BIL
DTED
Product-specific metadata and browse files
Access methods
NASA Earthdata Search for catalog discovery and supported downloads
NASA LP DAAC distribution and product landing pages
USGS EarthExplorer for search, preview, metadata export, and download
AppEEARS for supported subset and extraction workflows
Local GIS or raster-processing software after download and decompression
Quality and limits
Historical acquisition date limits current-condition interpretation.
Standard coverage excludes land outside approximately 60°N to 54°S.
Radar-derived elevations can represent vegetation, buildings, infrastructure, and other surface objects.
Void-filled products may include interpolation or auxiliary-source elevation rather than original SRTM observations.
Thirty-meter and ninety-meter cells can smooth narrow ridges, channels, road cuts, levees, and site-scale structures.
Terrain, radar geometry, water, shadows, layover, mosaicking, resampling, nodata handling, and vertical reference can affect results.
SRTM does not provide addresses, roads, buildings, land use, ownership, current hazards, or real-time elevation change.
Analysis workflows
Select SRTMGL1.003 or SRTMGL3.003 according to the study scale, processing budget, and terrain detail required.
Identify all tiles intersecting the area of interest and preserve product identifiers, acquisition metadata, and download dates.
Inspect nodata values, void-filled status, tile edges, vertical conventions, and anomalous cells before mosaicking.
Mosaic tiles and reproject only when necessary; select a suitable projected coordinate system for distance, area, slope, and hydrologic calculations.
Derive slope, aspect, hillshade, contours, relief, ruggedness, elevation bands, and terrain-position metrics.
Use hydrologic preprocessing to derive flow direction, flow accumulation, drainage divides, and watershed screening, while documenting every conditioning choice.
Join terrain statistics to roads, buildings, infrastructure, waterways, administrative regions, or service areas.
Compare SRTM against newer or locally authoritative elevation data for engineering, regulatory, flood, coastal, or site-scale decisions.
Publish the collection, resolution, tile list, void strategy, projection, resampling method, and derived-analysis parameters for reproducibility.
Value inside EDK
What NASA SRTM contains
The Shuttle Radar Topography Mission was a collaboration involving NASA, the National Geospatial-Intelligence Agency, and German and Italian space agencies. The mission used radar interferometry to estimate surface elevation from differences between radar signals observed by antennas separated by a known baseline. The resulting products form a digital elevation model covering most of the world’s land surface in the mission’s latitude range. (earthdata.nasa.gov)
The most commonly encountered collection is SRTMGL1.003, the 1 arc-second global product at approximately 30 meters. SRTMGL3.003 provides approximately 90-meter data. The broader SRTM family also includes non-void-filled and void-filled variants, water-body data, imagery-derived layers, and lower-resolution products. NASA’s LP DAAC catalog identifies these collections as elevation products with multi-day temporal resolution in its catalog metadata, but the underlying acquisition was concentrated in the February 2000 mission rather than being a continuously refreshed observation stream. (earthdata.nasa.gov)
- •Primary subject: surface elevation represented as a raster grid.
- •Common resolutions: 1 arc-second, approximately 30 meters, and 3 arc-seconds, approximately 90 meters.
- •Typical tile naming follows latitude and longitude, such as a one-degree tile covering a specific geographic cell.
- •The dataset is a terrain or surface-elevation model, not a road, building, address, land-use, or cadastral dataset.
Geography, acquisition date, and update cadence
SRTM collected data over most land surfaces between approximately 60 degrees north latitude and 54 degrees south latitude, representing about 80 percent of Earth’s land area. The mission was designed primarily for land topography, so water coverage is limited and was mainly collected for calibration. High-latitude areas outside the mission bounds, including much of Greenland and Antarctica, are not covered by the standard global SRTM acquisition. (usgs.gov)
The source observations were acquired during the Space Shuttle Endeavour mission launched on February 11, 2000, which flew for 11 days. Consequently, SRTM should not be described as current elevation or as a regularly updated monitoring dataset. NASA and USGS may revise processing, redistribute products, or provide different void-filled versions, but the source measurement date remains historical. There is no fixed recurring update cadence for new terrain observations in the original SRTM mission. (earthdata.nasa.gov)
- •Geographic coverage: approximately 60°N to 54°S over most land surfaces.
- •Acquisition period: February 2000.
- •Update cadence: no recurring observation cadence; later releases are processing or distribution updates.
- •Coverage gaps and quality vary by terrain, radar geometry, latitude, water, and the selected product version.
Formats and access methods
USGS identifies SRTM access through EarthExplorer, where users can search, preview, and download SRTM 1 Arc-Second Global, non-void-filled, and void-filled datasets under the Digital Elevation category. NASA’s LP DAAC documentation also identifies NASA Earthdata Search, USGS EarthExplorer, and LP DAAC distribution services as access paths. AppEEARS can be useful when users need a subset or standardized extraction rather than downloading and mosaicking many individual tiles. (usgs.gov)
Depending on the product and access route, users may encounter HGT files, GeoTIFF, BIL, or DTED. USGS describes the SRTM 1 Arc-Second Global distribution as available in DTED, BIL, and GeoTIFF formats. HGT tiles are also widely used in the SRTM ecosystem and are commonly distributed in compressed archives. Analysts should confirm the exact product identifier, file format, vertical reference, nodata convention, and processing status before building an automated pipeline. (usgs.gov)
- •NASA Earthdata Search: catalog discovery and download workflows.
- •USGS EarthExplorer: interactive search, preview, metadata export, and download.
- •AppEEARS: subset and extraction workflows for supported Earth-observation products.
- •Common formats: HGT, GeoTIFF, BIL, and DTED, depending on the collection and access path.
Suitable GIS and spatial-analysis workflows
A standard SRTM workflow begins by selecting the appropriate resolution and product variant for the study area. Download the tiles intersecting the area of interest, inspect metadata and nodata values, mosaic adjacent tiles, and reproject only when necessary. For distance, area, slope, or hydrologic calculations, analysts often work in a projected coordinate reference system appropriate to the region rather than treating geographic degrees as linear units.
From the elevation raster, GIS software can derive slope, aspect, hillshade, contours, ruggedness, local relief, elevation statistics, and terrain position. Hydrologic workflows may use elevation conditioning, flow direction, flow accumulation, watershed delineation, and stream-network derivation. These outputs are model results dependent on preprocessing choices; they are not direct SRTM observations. A defensible workflow records the SRTM collection, tile list, resampling method, void-filled or non-void-filled status, projection, vertical assumptions, and software parameters.
- •Terrain derivatives: slope, aspect, hillshade, contours, ruggedness, and relief.
- •Hydrology: flow direction, flow accumulation, drainage divides, and watershed screening.
- •Spatial joins: attach elevation statistics to roads, buildings, facilities, parcels, or regions.
- •Regional comparison: rank places or corridors by elevation, terrain variability, or slope exposure.
- •Quality control: inspect voids, edges, artifacts, vertical reference, and resampling effects.
Limitations, interpretation, and tradeoffs
SRTM’s largest limitation is temporal. The mission measured the Earth in 2000, so the product does not represent present-day terrain everywhere. It also measures a radar-derived surface that can be influenced by vegetation, buildings, infrastructure, slopes, radar shadows, layover, and other acquisition conditions. It should not automatically be interpreted as a bare-earth digital terrain model.
Resolution is another constraint. Approximately 30-meter cells are suitable for many regional analyses but can smooth narrow valleys, small drainage features, road cuts, levees, buildings, and other local structures. Void-filled products improve spatial completeness, but filling introduces modeled or auxiliary-source values rather than new SRTM observations. The SRTM user guide documents void-filling procedures that use auxiliary elevation information and interpolation, so users should distinguish original measurements from filled areas. (lpdaac.usgs.gov)
- •Historical acquisition limits current-change analysis.
- •30-meter resolution may miss or smooth small terrain and infrastructure features.
- •Radar-derived elevation can include vegetation, buildings, and other surface objects.
- •Void-filled areas may rely on interpolation or auxiliary elevation data.
- •Vertical references, nodata handling, resampling, and mosaicking can materially affect results.
Questions teams ask
Is NASA SRTM a digital elevation model or a digital terrain model?
SRTM is commonly used as a digital elevation model, but users should not automatically treat every cell as bare-earth terrain. Radar measurements can reflect vegetation, buildings, infrastructure, and other surface objects. For precise bare-earth analysis, compare SRTM with a product specifically designed and validated as a digital terrain model.
Does NASA SRTM cover the whole world?
No. Standard SRTM coverage includes most land between approximately 60° north and 54° south latitude, or about 80 percent of global land area. Areas outside that range, including much of Greenland and Antarctica, are not covered by the standard mission acquisition.
Is NASA SRTM updated every year?
No. The source observations were collected during the February 2000 Shuttle Radar Topography Mission. Archives may publish reprocessed, void-filled, or repackaged versions, but SRTM is not an annual or continuously updated elevation-monitoring dataset.
Which SRTM resolution should I use?
Use the approximately 30-meter 1 arc-second product when terrain detail and storage or processing capacity justify it. The approximately 90-meter product can be more efficient for continental, regional, or exploratory analysis. Resolution alone does not determine accuracy; also evaluate coverage, void filling, vertical reference, terrain type, and the decision the analysis must support.
Can SRTM be used for flood modeling?
SRTM can support watershed screening, drainage analysis, and terrain context, but it is not automatically suitable for regulatory flood modeling or site-scale hydraulic decisions. Its historical acquisition, surface-model characteristics, resolution, vertical uncertainty, and possible void-filled areas should be evaluated against newer and locally authoritative elevation data.
Keep exploring
hydrosheds
HydroSHEDS uses elevation-derived drainage structure and is a natural companion for watershed, river-network, basin, and hydrologic GIS analysis.
copernicus dem
Copernicus DEM provides another major global elevation resource and offers a useful comparison for surface-model selection, resolution, coverage, and access conditions.
Sources
NASA Earthdata LP DAAC: SRTM collection overview
NASA’s archive overview identifies SRTM’s mission, collaborating agencies, product families, resolutions, and catalog metadata.
Open sourceUSGS EROS Archive: SRTM coverage maps
USGS documents the latitude range, approximate land coverage, mission purpose, and EarthExplorer access.
Open sourceUSGS EROS Archive: Shuttle Radar Topography Mission
USGS describes SRTM product variants, resolutions, and available download routes.
Open sourceNASA SRTM Collection User Guide, Version 3
The official user guide documents collection processing and void-filling procedures.
Open sourceUSGS FAQ: Where can I get global elevation data?
USGS summarizes SRTM’s resolution, acquisition year, formats, and EarthExplorer access.
Open source