Utility · Unlisted
Grid reference stamping
Reads the GPS tags in a photograph, converts them to an MGRS grid reference, and burns that reference into the image for download.
Processing locality
No photograph, filename, EXIF metadata, GPS coordinate, MGRS coordinate
or generated image leaves this device. Once the module reports
offline ready, the core workflow needs
no network connection at all.
Diagnostics
Notes
- iPhone compatibility. Gridnorth v1 processes GPS-tagged JPEG photographs. HEIC/HEIF photographs are not yet supported. Before relying on Gridnorth offline, verify that your camera produces compatible JPEG images and test one while still connected.
- Large photographs are downsampled. Sources above roughly 20 megapixels are scaled down before stamping so the browser does not run out of memory. The coordinates are unaffected — a grid reference does not become more accurate by keeping 48 MP of pixels.
- Accuracy is bounded by the source. Consumer GPS tags are typically accurate to 3–10 m, which is why the default precision is 10 m. The grid maths agrees with the NGA reference implementation on 99.9% of test coordinates.
- The download carries no GPS tags. Re-encoding through a canvas discards all EXIF, so the stamped image shows the grid as visible text but is no longer machine-readable as a geotagged photograph.
- A stamped grid is a disclosure. Burning a location into an image makes it permanent and obvious. Consider where the file will travel before you stamp it.