Free online image georeferencer
Drop a map image, click matching points on it and on a live MapLibre map, and rooot viewer will warp the image into web-mercator and bake a tiled MBTiles you can use as a basemap. No install, no account, no queue. Same GDAL transform pipeline that QGIS uses, in your browser.
Open the georeferencer → or read on for the workflow.
What this tool does
It assigns real-world coordinates to a raster image so the image can be displayed in the correct geographic location on a map. The technical name for this is georeferencing, or sometimes rubber-sheeting when the warp is non-affine.
Common use cases: digitising historical maps for an archive, pulling drone orthophotos into a GIS without a desktop tool, anchoring a hand-drawn sketch to real coordinates, or turning a screenshot of a published map into a basemap layer.
How to use it
- Click Open the georeferencer. The viewer opens with the tool already active and a panel on the left of the screen.
- Click Choose image… and pick a PNG, JPEG, GIF, WebP, or TIFF (≤ 50 MB).
- Click a recognisable point on your image — a junction, a corner, a labelled landmark.
- Click the matching point on the map. That pair becomes one ground-control point (GCP). The streets and labels in the basemap on the right give you the geographic anchor.
- Repeat for at least 3-4 GCPs spread across the image. More is better, especially if the image was photographed (not scanned flat).
- Click Generate MBTiles. The warp runs server-side via GDAL and the .mbtiles downloads automatically — typically under a minute for a 5000×5000 px image.
You can drop the resulting MBTiles back into rooot viewer to render it on the 3D globe, or use it in TileServer-GL, QGIS, Mapbox Studio, Felt, or Avenza Maps.
Supported inputs and outputs
- Input: PNG, JPEG, GIF, WebP, TIFF — single raster, ≤ 50 MB.
- Output: MBTiles (SQLite tile pyramid, raster PNG tiles, EPSG:3857 / Web Mercator).
- Warp transforms: thin-plate spline (default, best for photographed paper maps), polynomial order 1-3, or pure affine.
- Zoom range: 0–18 (gdal sizes the pyramid by source resolution; tiny images cap earlier).
How it compares
| rooot viewer | MapWarper | QGIS Georeferencer | ArcGIS Pro | |
|---|---|---|---|---|
| Cost | Free | Free | Free | Paid |
| Install required | No | No | Yes (desktop) | Yes (desktop) |
| Account required | No | Yes | No | Yes |
| Output | MBTiles | GeoTIFF, KML, WMTS | GeoTIFF | GeoTIFF, MBTiles |
| TPS warp | Default | Yes | Yes | Yes |
| Queue / wait | None | Yes | None | None |
Privacy
The warp runs server-side because GDAL is server-side, but the input image and every intermediate raster are deleted as soon as the response returns. There is no per-user retention, no account, and no log of which user uploaded which image. The MBTiles download is the only output that persists, on your machine, until you delete it.
FAQ
What is image georeferencing?
Assigning real-world coordinates to a raster image so it can be displayed in the correct geographic location on a map. It's how scanned historical maps, drone imagery, and screenshots get pulled into a GIS.
How many ground-control points do I need?
At least 3 for an affine transform — enough for clean digital screenshots in a known projection. 4-8 GCPs spread across the image are recommended for the default thin-plate-spline (TPS) warp, which handles the non-affine distortion you get from photographed paper maps.
What is MBTiles?
An open SQLite-based container format for offline raster or vector map tiles, originally designed by Mapbox. A single .mbtiles file holds a full zoom pyramid plus metadata. TileServer-GL, MapTiler Server, the QGIS MBTiles provider, and Avenza Maps all render them.
Why thin-plate spline by default?
TPS handles non-affine distortions — the kind a photographed or imperfectly-scanned paper map exhibits — with a smooth bend rather than a stiff polynomial. For clean digital screenshots already in a known projection, an affine transform (3 GCPs) would be enough and is offered as an alternative via the API.
Are my images uploaded somewhere?
The image is uploaded to run the GDAL warp, but is deleted as soon as the response returns. No retention, no account, no log. The downloaded MBTiles is the only output that persists, on your machine.
What is the maximum image size?
50 MB per image. That's roughly a 5000×5000 px PNG at typical compression.
Can I edit GCPs after I've added them?
You can remove individual GCPs from the list (× button per row) and re-add them. Inline editing of an existing GCP's coordinates is on the roadmap.
What if my image isn't a map?
It still works as long as you can identify ≥ 3 points on the image whose real-world coordinates you know. Drone aerial photos, satellite captures, sketches with named landmarks, restaurant napkins — all viable.