dwg2geo-app

A browser app that turns a DWG drawing into a map layer. Upload a .dwg, pick its coordinate system, and see it rendered as GeoJSON on an interactive MapLibre map.

Live app: https://milkway.github.io/dwg2geo-app/

Everything runs in your browser

The conversion is dwg2geo — the audited, pure-Rust DWG→GeoJSON converter — compiled to WebAssembly. Your drawing is read and converted entirely on your device: the file is never uploaded to any server. The app is a static site.

How it works

1. Convert — the DWG bytes go to the WASM module, which returns a GeoJSON FeatureCollection in the drawing's local coordinates, plus a conversion report (feature counts, skipped/failed entities with reasons, warnings, bounding box).
2. Georeference — you choose the drawing's source CRS (SIRGAS 2000, WGS 84, SAD69 or Córrego Alegre UTM zones, or a custom proj4 string). A DWG has no reliable CRS field, but it often says its CRS somewhere — a title block reading UTM - SIRGAS-2000 - MC 33° W - FUSO 25 SUL, or a GEODATA object. The converter surfaces those declarations and the app reads them: when both datum and zone are stated, the CRS is prefilled and the quoted text is shown, so you can see exactly what the choice rests on. Anything weaker (only a zone, only coordinate magnitudes) is offered as a suggestion. The app reprojects every coordinate to WGS 84 in the browser with proj4js.
3. Map — the reprojected features are drawn on MapLibre over a free basemap (streets from OpenFreeMap — no API key — or Esri satellite imagery), styled with each entity's own CAD colour and line weight, with TEXT/MTEXT rendered as rotated labels. A floating Layers menu on the map lets you toggle each imported DWG layer (and the text labels), and the view fits the drawing's bounds. Click a feature to inspect its CAD properties.
4. Export — download the reprojected WGS 84 GeoJSON with one click, ready for QGIS, geojson.io, or any GIS pipeline.

Build & run locally

No Rust toolchain needed — the converter is the published dwg2geo npm package (the same audited core, compiled to WebAssembly), vendored into web/pkg/ at build time and self-hosted with the site:

./build.sh                          # fetches dwg2geo@<version> from npm into web/pkg
python3 -m http.server -d web 8080  # then open http://localhost:8080

To upgrade the converter, bump VERSION in build.sh. maplibre-gl and proj4 load from a CDN; the wasm bundle is served from this site's own origin (web/pkg/, git-ignored — regenerated on each deploy).

License

MIT (LICENSE-MIT). Bundles no LibreDWG/GDAL. The conversion core (dwg2geo + its dependencies) is permissive; the only weak-copyleft dependency is acadrust (MPL-2.0). See the dwg2geo licensing notes.