Elevation for a coordinate in Sweden

curl 'https://api.kart-api.se/v1/hojd?lat=58.705&lon=15.77'
{"lat":58.705,"lon":15.77,"hojd_m":24.39,"nodata":false,
 "attribution":["©Lantmäteriet · Markhöjdmodell · CC BY 4.0"]}

The value comes from Sweden's national elevation model (1 m grid, laser scanned), in metres above sea level in the RH 2000 height system.

The zero that isn't there

If there is no data at the point we answer "hojd_m": null and "nodata": true. Never 0. A zero in an elevation field reads as sea level, and whoever draws a profile across a mountain slope notices only when the curve dives into the sea in the middle of Jämtland.

Many points

One call per point, and points count against the quota. To profile a whole route or build your own terrain model, the archive beats a thousand lookups: fetch the municipality's terrain archive (/v1/tiles/terrain-rgb-{code}-1m.pmtiles) and read it locally. 301 archives exist, one per municipality plus a few named towns.