Overview
Maidenhead Grid Locator converts geographic positions into compact QTH grid locators used by amateur-radio operators. The tool can read the map center, use a location supplied by your device, search for a place, convert coordinates, or move the map to an existing locator.
The normal output is a six-character locator such as OL63pd. Locator input accepts 2, 4, 6, or 8 characters so broader fields and more precise extended grids can also be inspected.
How to use it
- Drag, zoom, or tap the map. The fixed crosshair reports the map-center latitude, longitude, and six-character grid.
- Press Use my location only when you want the browser to request device location permission.
- Submit a city, place, or street address, then choose one of up to five results.
- Enter decimal coordinates or a common degrees-minutes-seconds pair and press Show on map.
- Enter a 2, 4, 6, or 8 character locator to move to its center and outline its boundary.
- Copy the coordinates or canonical six-character locator when needed.
Encoding mechanics
The conversion uses WGS 84 latitude and longitude. Maidenhead divides the world successively into 20-by-10 degree fields, 2-by-1 degree squares, 24-by-24 subsquares, and optional 10-by-10 extended squares. Longitude is encoded first in every pair.
A six-character cell covers 5 minutes of longitude by 2.5 minutes of latitude. The displayed locator uses uppercase field and square characters with lowercase subsquare letters. Calculations run locally in the browser.
Precision and boundaries
Map coordinates are displayed to six decimal places, but this does not imply survey-grade accuracy. Device GPS accuracy, address geocoding, map data, and the physical size of a six-character cell all limit the practical result.
The implementation clamps the poles, handles the international date line, validates every locator character range, and uses the center of a supplied grid when moving the map.
Privacy and map providers
GPS coordinates and Maidenhead conversion remain in your browser and are not uploaded to CW599. First-party analytics may record that a generic action was used, but it does not record an address, coordinate, GPS position, or locator.
Address text is sent to the CW599 server only after form submission. CW599 forwards it to the public Nominatim service through a rate-limited proxy and caches only the returned result for seven days under a one-way query key. OpenStreetMap tile servers receive the browser IP address and the tile area requested as part of ordinary map delivery. OpenStreetMap attribution remains visible on the map.
Availability and fallback
OpenStreetMap tiles and public Nominatim search are best-effort community services. Search coverage, spelling, language, and response time vary by region, and access from some networks may be slower. There is no automatic address suggestion or bulk lookup.
If map tiles or address search are unavailable, coordinate-to-locator and locator-to-coordinate calculations continue to work in the browser. Device location requires HTTPS, browser support, and user permission.
Versions and archives
v1.0 introduced the interactive map, six-character center readout, browser location, submitted address search, coordinate parsing, 2/4/6/8 character locator input, bilingual documentation, and privacy-limited server proxy.
Version archive
When a retired release has a runnable snapshot, this list will link both its documentation and the archived tool. Earlier releases without a snapshot are explicitly marked documentation only.