OkMap Tutorial - Georeferencing a Raster Map
Published on April 15, 2026 - Video duration: 5:43
Tutorial Overview
OkMap tutorial for georeferencing raster and topographic maps using control points and coordinate reference systems (CRS).
OkMap can be used as georeferencing software for historical, hiking, and topographic maps.
In this video, we will show how to associate a map with real-world geographic coordinates using EPSG codes, control points and advanced georeferencing tools.
To obtain accurate results, it is necessary to know the map's Coordinate Reference System (CRS) and provide at least three control 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 high-quality topographic maps to achieve more accurate georeferencing
- 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