GridPoint — Location Format Explorer

A web application for converting between location formats and visualising points on an interactive map.

Screenshot

Supported Formats

Format	Input	Output
Latitude/Longitude — Decimal Degrees	✅	✅
Latitude/Longitude — Degrees Minutes Seconds	✅	✅
Latitude/Longitude — Degrees Decimal Minutes	✅	✅
Maidenhead Grid Locator	✅	✅
UK Postcode	✅	—
Town / Place Name	✅	—
OS Grid Reference	✅	✅
WAB Square	✅	✅
What3Words	✅*	—
CQ Zone	—	✅
ITU Zone	—	✅
Plus Code	✅	✅

*What3Words input requires an API key (free tier available).

Quick Start

With Docker Compose (recommended)

docker-compose up --build

Then open http://localhost:8080

With Docker directly

docker build -t gridpoint .
docker run -p 8080:8080 gridpoint

To change the port

docker run -p 9000:8080 gridpoint
# then open http://localhost:9000

What3Words Setup (Optional)

1. Get a free API key at https://developer.what3words.com
2. Set it in docker-compose.yml:

   environment:
     - W3W_API_KEY=your_key_here

   Or export it before running:

   export W3W_API_KEY=your_key_here
   docker-compose up

Usage

To locate a point:

1. Select an input format from the dropdown
2. Enter the location value(s)
3. Press LOCATE or hit Enter

To decode a map point:

• Click anywhere on the map — all formats for that location appear in the sidebar

To copy a format:

• Click the ⧉ icon next to any result

Notes

• OS Grid Reference, WAB Square conversions apply to Great Britain only
• What3Words input requires API key; all other formats work offline
• UK Postcode lookup uses the free postcodes.io API
• Town/place lookup uses OpenStreetMap Nominatim
• CQ and ITU zones are calculated algorithmically (±1 zone accuracy near boundaries)

Running Without Docker

cd app
python server.py

Requires Python 3.8+ — no additional packages needed.

Author

Built by James Marshall (M0LZN) — m0lzn.com