How to Georeference a Scanned Paper Map

Last checked November 1, 2026

A scan or phone photo of a paper map (a club trail map, an old quad, a trailhead board) has no coordinates in it, so no app can put your GPS position on it. Georeferencing fixes that: you tell the app where a few points on the picture are on the ground, and it works out where every other point is. In Cartahaven it takes a few minutes and three or more taps on each map.

Before you start

A good image. Scan flat if you can. A photo works; take it square-on, with the whole map in frame. Cartahaven imports JPEG, PNG and WebP pictures and PDFs; save an iPhone HEIC photo as a JPEG first.
A connection, for now. The world map you match points against loads online. Once saved, the map works offline like any other. With no signal you can still type coordinates for each point.
Recognizable spots. Road junctions, bridges, peaks, lake outlets, trailheads, grid-line crossings: anything you can find both on your map and on a modern map.

Step by step

Import the map. In the map app, tap “Import” and pick the picture or PDF. A picture opens straight into placing it. If the photo was taken with GPS on, the app first asks what it is: choose “Use as a map”. (Import map photos one at a time: several geotagged photos at once become placemarks.) For a map already in your library without a location, open its ⋯ menu and choose “Add location”.
Tap a spot on your map (the top half of the screen), then the same spot on the world map below. That is one point. Use the search box (“Jump to a place, or lat, lon”) or “My location” to get the world map to the right area, and switch it between Streets, Topo (US) and Satellite (US), whichever shows your spot best.
Or type the coordinates. If the map has grid ticks or a marked survey point, tap “Type coordinates” for that point instead of tapping the world map. Latitude and longitude (for example 41.1624, -74.3325), UTM and MGRS grid references are all accepted.
Place at least three points, spread out. Toward the corners of the map is best. Points in a near-straight line (all along one road) can’t fix the map; the app says so and asks for one well away from the others.
Add a fourth point to check the fit (see below), then tap Save. Your position now shows on the map.

Reading the fit

With exactly three points, the map is placed exactly through them, so there is nothing to check them against: the app says “Placed” and suggests a fourth point far from the others. From four points on, it shows a typical error in meters or feet, and each point’s own error. The dashed outline on the world map shows where the whole sheet lands.

A few meters to a few tens of meters is normal for a hand-drawn or scanned map: the app says “Looks good” up to 50 m.
Over 50 m, the app flags the worst point: “A point looks off: drag it, or remove it.” Usually one tap landed on the wrong junction. Drag the pin on either map to move it, or remove it with ✕.
Over 100 m, Save asks you to confirm, because your position on the map may be that far off.

With six or more points, the app can also correct for a photo taken at an angle, when that fits the points far better than a flat placement. More well-spread points make the error estimate more trustworthy.

A paper map is only as accurate as it was drawn. Old or sketch maps can be off by more than any fit can fix: check your position against what you see on the ground, and carry a second map you trust.

Fixing it later

To move the points again, open the map’s ⋯ menu in your library and choose “Adjust location”. Your saved points come back, ready to drag, remove or add to.

For map publishers

If you sell or share maps that have no georeferencing, the uploader in the publisher dashboard has the same tool: click a spot on your map, then the same spot on a real map, three or more times, and the result is written into the PDF as standard geospatial registration, so the file carries its location with it. See selling your maps.

Next: using your maps offline, or the help page on photos and scans.