# RavingDesk Coordinate Converter (DMS, UTM, MGRS, plus codes)

> Convert coordinates between DD, DMS, UTM/UPS, MGRS, geohash, Maidenhead and plus codes. Reads coordinates in almost any notation — decimal degrees, degrees-minutes-seconds with hemisphere letters, UTM or UPS, MGRS grid references, geohashes, Maidenhead locators, plus codes or Web Mercator metres — and writes each one in every other format, with the UTM zone (including the Norway and Svalbard exceptions), meridian convergence and scale factor. Up to 500 lines at once, with a CSV table for spreadsheets. It is the coordinate engine of RavingDesk’s Data & charts geo layer.

Part of usefulweb.app (https://usefulweb.app/). Part of [RavingDesk](https://ravingdesk.usefulweb.app/) (ownerApp: ravingdesk). Results are deterministic calculations from the inputs and the listed assumptions; the API returns exactly what the web page shows.

## Use it
- Human interface: https://ravingdeskcoordinateconverter.usefulweb.app/ (interactive tool at https://ravingdeskcoordinateconverter.usefulweb.app/tool)
- JSON API: POST https://ravingdeskcoordinateconverter.usefulweb.app/api/v1/calculate with a JSON object of inputs (schema: https://ravingdeskcoordinateconverter.usefulweb.app/api/v1/tool)
- OpenAPI: https://ravingdeskcoordinateconverter.usefulweb.app/openapi.json
- MCP (Streamable HTTP): https://ravingdeskcoordinateconverter.usefulweb.app/mcp - tool `ravingdesk_coordinate_converter`

## Inputs
- coordinates (textarea, required): Coordinates (one per line) - Up to 500 lines. Each line is converted on its own; a line that cannot be read is reported and skipped.
- from (select): Input format
- mgrsDigits (integer): MGRS precision (digits per axis) - 5 = 1 m, 4 = 10 m, 3 = 100 m.
- plusCodeLength (integer): Plus code length - 10 digits ≈ 14 m × 14 m, 11 ≈ 3.5 m × 2.8 m.
- geohashLength (integer): Geohash length - 9 characters ≈ 4.8 m × 4.8 m.

## Method
- Latitude/longitude text is read tolerantly: decimal degrees, DMS and DDM with °, ′, ″ (or d, m, s, apostrophes), hemisphere letters before or after the numbers, minus signs, and decimal commas when the two values are separated by a semicolon.
- UTM uses the transverse Mercator projection with Krüger’s series to 6th order in the third flattening (Karney 2011: accuracy better than 5 nm within the zone), k₀ = 0.9996, false easting 500 km and false northing 10,000 km south of the equator. Zones follow the Norway (32V) and Svalbard (31X–37X) exceptions. North of 84°N and south of 80°S the polar stereographic UPS (k₀ = 0.994) is used.
- MGRS uses the standard (AA) lettering of NGA.STND.0037 and truncates to the chosen precision, as the standard requires; MGRS in the polar UPS areas is not supported. Plus codes follow the Open Location Code specification; geohash interleaves longitude/latitude bits in base 32; Maidenhead uses fields, squares and subsquares.
- Grid codes (MGRS, plus codes, geohashes, locators) stand for a square: the latitude/longitude shown is the centre of that square and the cell size is reported.
- Web Mercator (EPSG:3857) treats the Earth as a sphere of 6,378,137 m; it is for web maps, not for measuring.