SRTM HGT Elevation Tile

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: elevations come from the global Copernicus DEM GLO-30 model with a step of about 30 meters — the tiles hold real terrain, not a placeholder. The delivery is a ZIP archive: inside are the full degree tiles covering your area, each under its canonical name of the N55E037.hgt kind. They must not be renamed — the georeferencing lives in the file name. Tiles become flat only where there is no coverage at all, such as the open ocean.

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 the heights actually are: Copernicus GLO-30 is a surface model (DSM), not bare ground — over forest it is the tree canopy, over built-up areas the roofs. Acquired in 2010–2015 and released in 2021, so a fresh embankment or a demolished block will not show. The sea is written as zero (0 m) in the source tiles.