---
title: "Unsupported coordinate system"
description: "Fix the unsupported coordinate system error. Convert the file to EPSG:4326 or EPSG:3857 in another tool, then import it again."
---

If processing reports an unsupported coordinate system, MangoMap cannot reproject the file from its current CRS. Convert the file to `EPSG:4326` or `EPSG:3857` in another tool, then import it again.

## Most likely cause: file uses a regional or custom projection

MangoMap reads the input coordinate system from your file (`.prj` for shapefiles, the GeoJSON `crs` member, the embedded SRS for other formats). The error appears when the projection in your file isn't one MangoMap recognises — typically a custom datum, a regional grid, or a vendor-specific code.

**How to verify.**

Check the projection declared in your file:

- **Shapefile:** open the `.prj` in any text editor. The first part of the WKT is the projection name (e.g. `PROJCS["NAD83 / Wisconsin South..."`).
- **GeoJSON:** look for a `"crs"` member at the top level. Standard GeoJSON should not include it; if it does, the value identifies the projection.
- **Other formats:** open in QGIS (`Layer → Add Vector Layer`); the layer's CRS is shown in the bottom-right of the QGIS window.

MangoMap can transform many recognised coordinate systems. Reproject only when the declared CRS is malformed or the import reports that it is unsupported.

**Fix.**

Reproject to `EPSG:4326` before re-importing.

**In QGIS:**

1. Add the file as a layer.
2. Right-click the layer → `Export → Save Features As`.
3. Set `CRS` to `EPSG:4326`.
4. Save and upload the new file to MangoMap.

**On the command line:** run the command for your file type.

- Shapefile:

  ```console
  $ ogr2ogr -t_srs EPSG:4326 output.shp input.shp
  ```

- GeoJSON:

  ```console
  $ ogr2ogr -t_srs EPSG:4326 output.geojson input.geojson
  ```

- Raster (GeoTIFF):

  ```console
  $ gdalwarp -t_srs EPSG:4326 input.tif output.tif
  ```

## Less common: `.prj` file says one thing, data is in another

Occasionally a shapefile has a `.prj` that doesn't match the actual coordinates — typically because the file was reprojected with a tool that didn't update the `.prj`. MangoMap trusts the `.prj`, so the data ends up in the wrong location even if processing succeeds.

**How to verify.**

Open the shapefile in QGIS. If the features draw in the wrong place when QGIS reads the `.prj`, the declaration is wrong.

**Fix.**

Set the correct CRS in QGIS (`Layer → Set CRS`), then export to a new shapefile. The new export's `.prj` will match the data.

## If none of the above

If your data is already in `EPSG:4326` or `EPSG:3857` but you still see this error, the file may have a malformed CRS declaration. Open in QGIS, confirm the layer reads correctly, then export again — the QGIS export will write a clean CRS.

## Related

- [How importing data works in MangoMap](/docs/importing-data/concepts-importing-data) — explains why MangoMap reprojects everything to Web Mercator.
- [How to import a shapefile](/docs/importing-data/import-shapefile)
- [Supported file formats and limits](/docs/importing-data/supported-formats)