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.
- Use the map-source switch at the top-left of the map to choose AMap or OpenStreetMap. Inside mainland China the tool defaults to AMap automatically, but you can switch at any time; the choice is remembered on this device.
- 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.
The map shows AMap inside mainland China and OpenStreetMap elsewhere. The default source is chosen automatically from your region, and the map-source switch (top-left) lets you change it on demand; the choice is remembered in this browser. In AMap mode, the AMap JavaScript API loads from amap.com and AMap’s own terms and privacy policy apply; AMap receives the browser IP and the map area requested as part of ordinary map delivery, and its attribution is shown on the map. In OpenStreetMap mode, OSM tile servers receive the browser IP and requested tile area, and OSM attribution remains visible.
Address text is sent to the CW599 server only after form submission. For Chinese-locale searches, CW599 forwards the address to AMap’s geocoding Web Service, converts the returned GCJ-02 coordinates back to WGS 84 so the pin matches the grid overlay, and returns the result to the browser. For other searches, the address is forwarded to the public Nominatim service through a rate-limited proxy. Either way, only the returned result is cached for seven days under a one-way query key.
Availability and fallback
OpenStreetMap tiles and public Nominatim search are best-effort community services. Coverage, spelling, language, and response time vary by region, and OpenStreetMap tiles may load slowly or be blocked on some networks in mainland China. Inside China, the tool uses AMap instead, which loads from domestic servers. Automatic address suggestions and bulk lookup are not provided.
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
v1.2 adds China-friendly mapping. The tool now detects the visitor region and defaults to AMap inside mainland China while keeping OpenStreetMap elsewhere, and a map-source switch (top-left of the map) lets you change the base map at any time and remembers the choice on the device. Address search routes Chinese-locale queries to AMap geocoding with GCJ-02 to WGS 84 conversion so pins match the grid overlay. The grid outline and the location pin both reconcile WGS 84 with AMap’s GCJ-02 coordinates. OpenStreetMap tiles and Nominatim remain for non-Chinese use. v1.1 aligned the narrow-screen content gutter with the site header. 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.
Changelog · September 7, 2026
Added consent-aware anonymous tool-open and applicable activity counters or durations. No leaderboard or change to the tool’s calculation, audio or CW Room communication identity was introduced. No audio, answers, location inputs or raw browser IDs are stored in analytics. Unique browsers are estimates, not people. Previously archived documentation remains available below; code history is retained in Git and private deployment backups.
Site changelog · Spanish support
September 20, 2026: the homepage, all eight Morse Lab tools and their current help pages now support Spanish. State, error, permission and optional leaderboard messages are localized; audio, scoring, identities and saved results are shared and unchanged. Guides, articles, shop, account and legal destinations remain in English and are labeled accordingly. Historical help keeps its original languages. Analytics recognizes Spanish routes and respects the same privacy choices without collecting new fields.
Site changelog · Japanese support
September 22, 2026: all eight Morse Lab tools and their current guides now support Japanese. The existing Japanese homepage and interface copy have been reviewed, including dynamic feedback, errors, accessibility, permissions and voluntary leaderboard publication. Audio, scoring, shared identities and saved results are unchanged. English, Chinese and Spanish remain available. Untranslated destinations are labeled as English. Existing Japanese Letter Trainer archives remain available; other historical guides retain their original languages. No new data fields or permissions are introduced.
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.