OkMap Tutorial - Georeferencing a Raster Map

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.

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