OkMap Tutorial - Georeferencing a Raster Map
Published on April 15, 2026 - 6 minute read
OkMap tutorial for georeferencing a raster map using control points and a coordinate reference system (CRS).
The required parameters are the map Coordinate Reference System (CRS) and at least 3 georeferencing points with known coordinates.
Recommended prerequisite
To better understand this tutorial, we recommend watching first:
Procedure:
- Load the raster map into OkMap
- Define the reference system (CRS: datum, projection or EPSG code)
- Set the grid interval (metric or geographic)
- Insert control points with known coordinates
- Apply georeferencing
- Verify grid alignment
- Save the georeferenced map
- Check the map in Google Earth
Tips:
- Use EPSG code or name filter to select the correct CRS
- Insert at least 3–4 points (5–6 recommended for higher accuracy)
- Distribute points across the entire map
- Avoid collinear points
- Use clearly identifiable points (grid intersections or, alternatively, peaks or road crossings)
- Always verify the final result in Google Earth
Common errors:
- Setting an incorrect CRS (most frequent error)
- Placing points too close or poorly distributed
- Using imprecise or hard-to-identify points
- Not assigning coordinates to control points (common mistake on the last point)
- Not applying georeferencing after inserting points
- Assuming grid alignment is sufficient without external verification