Geohash decoder

Model: Base-32 decode to interleaved bisection bits

Accuracy: Exact

When to use this: Use this when a geohash turns up in a database key, a log line, or an API response and you need the ground it stands for: the center of its cell, the bounding box, and the error margins either side, so the precision is explicit rather than implied by the string's length. It is also how a stored key is checked: decoding the geohash shows the area a row actually covers, which is what tells you whether the precision chosen for the index suits the query.

Limitations: A geohash is a cell, not a point: six characters is roughly 1.2 km by 0.6 km, and the center is a convenience. Cells are rectangles in latitude and longitude, so their ground width shrinks toward the poles, and two points close together can sit in cells whose strings share no prefix, which matters when prefixes are used for proximity. The error margins it reports are half the cell in each direction, which is the honest uncertainty of any point derived from a geohash.

Worked example: dppn5fyxx. Source: Inverse of the encode scenario. It is golden test vector v001, and every build checks the tool still gives its answer within its tolerance.

Review: Not yet independently reviewed by a GIS professional.

Last verified: 2026-09-18, when a maintainer last confirmed this tool's sources at the issuer. See the sources ledger.

Status: version 1.0.0, core 0.1.0. See this tool in the verification report.

Changes

• 2026-09-19, changed: Every indexing tool is now stable. Geohash decode and neighbors match pygeohash on 1,000 and 500 cases; the Plus Code tools pass every row of the Open Location Code test data; tile ground resolution matches the Bing Maps table; the H3 resolution chooser matches H3's resolution table; and H3 polygon fill gives H3 C's own test counts (1,253 cells, 1,214 with a hole). Results are unchanged apart from the fix below. Changelog

Checked against: 24 golden test vectors (download the test vectors, each with its source and tolerance). See how results are checked and every source.

Sources

• Geohash (public domain algorithm), Niemeyer, G., geohash.org, Original description, as archived (the site is gone). Base-32 alphabet 0123456789bcdefghjkmnpqrstuvwxyz, longitude bit first.