alt Hacker NewsGeoJSON is not just for geographical features! Shapes of any kind work just as well.
QuPath[1], a tool for digital pathology whole slide image analysis, can export annotations in GeoJSON format (and import too I suppose).[2] This makes it really very easy to make annotations transportable between tooling.
[2] https://github.com/qupath/qupath-docs/blob/main/docs/advance...
The spec states:
> The coordinate reference system for all GeoJSON coordinates is a geographic coordinate reference system, using the World Geodetic System 1984 (WGS 84) [WGS84] datum, with longitude and latitude units of decimal degrees.
So that seems to be a misuse of the format. Using a geojson library for this may get you into trouble with ranges or antimeridian cutting.