How to Georeference a Map in OOMapper

In layman's terms, Georeferencing a map means identifying the Latitude and Longitude coordinates of a point on the map so that if you use a GPS-enabled app, it will be able to tell which spot on the map you are located at in real life. Older orienteering maps are not georeferenced, so here is one method of georeferencing a map so that you can use it in GPS-enabled apps such as MapRun6 or GPSO:

  1. Download the latest Stable Release of Open Orienteering Mapper software from

  2. From the menu, select Map>Georeferencing. If the map has already been georeferenced, the dialog box will look something like this:

If the map has not yet been georeferenced, the Coordinate Reference System will probably say "local" and most of the fields will be 0.

To georeference the map:

  1. Save the map file using File>Save As to a new file so you don't mess up the existing version of the map.

  2. From the menu, select Map>Rotate and rotate the map until grid north is at the top of the page. The original map was probably rotated so that magnetic north is at the top of the page, so you probably need to rotate the map about -15 to -20 degrees to get grid north at the top. For most of our maps, there will be roads or paths aligned with grid north so they should now be vertical on the page, but if you have no way of telling where grid north is, you could use something like Google Earth (Pro) or ask a mapper for assistance.

  3. From the menu, select Map>Georeferencing.

  4. Change "Coordinate Reference System" to "by EPSG Code" and enter "3857" in the next field and click the "OK" button. This is reference system used by Google Maps/Earth and a lot of apps.

  5. Find a point on the map (ideally near the center of the map) that is easily recognizable from a satellite view on Google Earth or Google Maps so that you can find the precise longitude/latitude coodinates. (e.g. a corner of a building or paved area, or a tower, or other permanent feature).

  6. Click the button "Pick on Map", zoom in to the area on the map, and click the cursor at the point you have identified.

  7. Locate the point in Google Earth (Pro) or Google Maps Satellite View by clicking on the exact spot and noting the longitude and latitude coordinates that are displayed in degrees and decimal degrees (e.g. 51.017806, -114.143891).

  8. In Mapper, enter the first of these coordinates (e.g. 51.017806) into the first field in "Geographic Coordinates" and the second part (e.g. -114.143891) in the second field. The EPSG coordinates will be filled in automatically (see screenshot example above).

  9. Under Map North declination, click the "Lookup..." button and click "Yes".

  10. Verify that the map on the website that opens shows roughly the correct spot and note the number of degrees of declination shown on the page (e.g. 13.92° E).

  11. In Mapper, enter the declination noted above in the Declination field (e.g. 13.92°). A positive value is used for east declinations, enter a negative for west declinations).

  12. When Mapper asks you if you want to rotate the map, choose "Yes" and accept the default settings. The map will now be rotated so that the current magnetic north is at the top of the map.

  13. If the magnetic north declination has changed from when the map was created, you will need to rotate any magnetic north lines on the map (blue or black vertical lines) so that the lines are now vertical. You might also need to rotate text. Note: mapper now has a pattern symbol for magnetic lines which allows you to draw a box that gets automatically filled with the properly spaced lines rather than creating magnetic lines manually. To locate this pattern symbol, you may need to load it from the built in mapper symbol files.

  14. Save the file.

  15. Optional: if you want to generate a KMZ file for uploading to MapRun, you now need to enter zero in the Magnetic Declination field and choose "Yes" to rotate the map back to grid north before choosing File>Export As>KMZ. Choose the default 512x512 pixel tiles and set the DPI to 150 or 200 resolution to ensure the KMZ file size is less than 1MB. If you save the mapper file at this point, make sure you use a different file name and note in the filename that the top is grid north or only for use for MapRun importing.