What is the HGT file format?
An .hgt file stores a single tile of SRTM (Shuttle Radar Topography Mission) elevation data in a raw binary format. SRTM data was collected in February 2000 during Space Shuttle Endeavour mission STS-99, when NASA and the National Geospatial-Intelligence Agency (NGA) mapped Earth's surface between 60°N and 56°S using interferometric synthetic aperture radar.
The file has no header, no magic bytes, and no embedded metadata. It is a flat, row-major array of signed 16-bit big-endian integers, each representing terrain elevation in meters relative to the WGS84 geoid. Rows scan west-to-east and north-to-south. Void cells (areas with no valid measurement) are encoded as -32768.
Each .hgt file covers exactly one 1°×1° geographic tile. The filename encodes the SW corner: N48E016.hgt covers 48°-49°N, 16°-17°E. Two resolutions exist: SRTM3 (3-arc-second, ~90 m spacing, 1201×1201 grid, ~2.8 MB per tile) and SRTM1 (1-arc-second, ~30 m spacing, 3601×3601 grid, ~25 MB). SRTM Version 3.0 (SRTM Plus, 2015) extended global 1-arc-second coverage and filled many previously void areas.
GDAL opens .hgt files natively and recognizes the naming convention automatically. A typical workflow mosaics multiple tiles and exports to GeoTIFF for analysis in QGIS, ArcGIS, or Global Mapper. Improved successors include NASADEM (2020) and Copernicus DEM (2022).
Security & safety
RISK: LOWRaw binary numeric data with no executable content. Zero security risk from the file itself. Data is freely provided by a US government agency (USGS/NASA).
Format details
in a nutshell- Garmin HGT/TYP Terrain Data - Some Garmin GPS map products use .hgt sidecar files for terrain shading - different structure than SRTM.
Programs that open HGT files
Windows5 apps
Global Mapper
Paid File > Open Data Files, select the .hgt - renders elevation as a colored DEM or hillshade. 
SRTM Void Killer
Free Specialized tool for filling void cells (-32768) in HGT files using interpolation. 
ArcGIS Desktop / ArcGIS Pro
Paid Add the .hgt as a raster layer; ArcGIS reads SRTM HGT via its GDAL-based raster engine. 
macOS1 app
Linux3 apps
GDAL (gdal_translate / gdalinfo)
Open-source gdalinfo N48E016.hgt inspects metadata; gdal_translate converts to GeoTIFF. Technical details
deep spec| Encoding | Raw binary - flat array of signed 16-bit integers, no header |
| Byte order | Big-endian (network byte order) |
| Sample type | Signed 16-bit integer; value represents elevation in meters (WGS84 geoid) |
| Grid scan order | Row-major; west-to-east columns, north-to-south rows |
| Void value | -32768 (no valid measurement for that grid post) |
| SRTM3 grid size | 1201×1201 posts per 1°×1° tile (~2.8 MB per file) |
| SRTM1 grid size | 3601×3601 posts per 1°×1° tile (~25 MB per file) |
| Tile coverage | One 1°×1° geographic tile per file |
| Filename convention | SW corner encoded: N48E016.hgt covers 48-49°N, 16-17°E |
| Tile edge overlap | Adjacent tiles share one row/column of boundary posts |
| Spatial resolution | SRTM3 ~90 m; SRTM1 ~30 m (at equator) |
| MIME type | application/octet-stream |
| Released | 2003 (SRTM data publicly released by USGS/NASA) |
| Latest version | SRTM Version 3.0 (SRTM Plus, 2015) - voids filled |
| Open standard | Yes · royalty-free |
| Specification | www2.jpl.nasa.gov |
HGT conversions
Community Q&A
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