SRTM HGT Elevation Tile
Open BetaHGT is NASA's native SRTM elevation format: a raw array of 16-bit signed big-endian integers, a 1°×1° tile (1201×1201 for SRTM3 or 3601×3601 for SRTM1), no header, with the filename encoding the south-west corner (e.g. N55E037.hgt). On osm2cdr the HGT export works honestly like this: if the project contains a DEM raster layer, elevations are sampled from it on a grid; if no DEM layer is present, a FLAT placeholder tile with uniform height is written. No built-in SRTM source is bundled into HGT, so real relief appears only when an elevation layer is supplied. The file is read by GDAL, QGIS, OsmAnd, Locus Map.
Key Features
About SRTM HGT Format
HGT is the elevation format of the SRTM mission: a tile one degree by one degree, written as a raw array of sixteen-bit signed numbers, with no header at all. The program takes the georeferencing from the file name: N55E037.hgt means the tile whose south-west corner sits at 55 degrees north and 37 degrees east. The grid size tells you the version: 1201x1201 is SRTM3 with a step of about 90 meters, 3601x3601 is SRTM1 with a step of about 30 meters.
The format is taken when a program reads specifically .hgt: offline navigators for elevation profiles, terrain processing tools, simulators, your own scripts. The structure is so simple that the file can be parsed in a few lines of code without libraries.
Something important about our export: no SRTM source of our own is baked into the HGT. If the project has an elevation layer, values are sampled from it on the tile grid; if there is no such layer, the file will still be correct in structure and name, but flat — with a uniform elevation. Real terrain in that case is taken from the open SRTM or Copernicus sources, and we have a ready-made hillshade as a separate format.
Empty values are written as the number -32768 — the accepted SRTM notation for no data. The file is read directly by GDAL and QGIS, while offline navigators such as OsmAnd and Locus Map expect it in their own terrain folder.
What Program Opens SRTM HGT Files
The following programs and applications can open, edit, and work with SRTM HGT Elevation Tile (.hgt) files exported from OSM2CDR:
Format specifications
- Open standard
- 3D coordinates supported
- Lossless (no quality loss)
- No attributes
- Output: 1 file
- A raw SRTM .hgt tile of 16-bit signed big-endian integers (1201x1201 or 3601x3601), named from the bbox SW corner; heights from a project DEM or a flat placeholder if none.
Who Uses SRTM HGT Maps
How to Export SRTM HGT
How to Open After Export
- GDAL — gdalinfo -stats N55E037.hgt shows the grid size, the extent and the elevation range: the first check of whether the tile holds real terrain.
- QGIS (free) — drag the .hgt into the window as a raster, then Raster → Analysis → Hillshade or Contour to see the terrain in a familiar form.
- OsmAnd and Locus Map — put the file into the application's terrain folder on the device: the elevation profile will appear in routes offline.
- Conversion — gdal_translate -of GTiff N55E037.hgt dem.tif turns the tile into GeoTIFF if your tool does not understand the raw format.
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Frequently Asked Questions
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