O. Georeferencing Images and Maps

Owned by Erlend Kvinnesland
Last updated: Sept 23, 2013
2 min read

Introduction

This tutorial will guide you through the process of georeferencing a map. To georeference a map or image you need at least 3 tie points. These points should cover as much of the map as possible. In this tutorial we will use a map from Geoscience Australia. In this map we will use the crossing points between the graticules as tie points. This map is in WGS84, Mercator Central Meridian 126, Latitude of True Scale 13

Exercises:

Exercise

Import an image into your project

  1. Create a Generic folder (i.e. a folder with schema Generic) and rename that folder to Maps or something similar.
  2. Right-click the new folder and go to Import > Generic. Browse for the image AMJ_70183.png in the folder \data\06Maps\ and click Open
  3. Make sure the schema of the image set to Image Data.
  4. Click Execute
Exercise

Georeference an image

  1. Right click the imported image and select Geo Reference. A two windows will pop up.
  2. Set the geodetic properties of the map to WGS84, Mercator Central Meridian 126, Latitude of True Scale 13
  3. Click Next
  4. Set Method: to Scale and Translate
  5. Set Tie point Coordinate Format: to 12.3456 N/S
  6. Find a graticule crossing point, look for the values and type them in Lat Lon
  7. Now zoom in to the same area in the standalone window, click Image pick and click on the crossing point in the image.
  8. Change the drop down to Tie point 2, find a new tie point, type in the values and pick the point
  9. Repeat the same step for Tie point 3
  10. After selecting 3 tie points you should be able to see the Pixel error, which represents the accuracy of the georeferencing. The value should not exceed more than 1 pixel on each point as a general rule.
  11. Click Finish. 
  12. Now transform the image to UTM zone 51 S