What is Georeferencing?

Georeferencing of historical map images involves assigning spatial information so that they align with real world geography. The essential process typically consists of adding control points to an historic map that have a real-world location; once there are sufficient control points, the historic map can be transformed so that it correctly aligns with geographic reality (Fleet et al., 2012).

What is the Use of Georeferencing?

  • Georeferencing data render maps more discoverable, supporting map-based searching and presentation of the collection applicable in any geographic interface, the way researchers prefer to find and look at maps.
  • Gazetteer searching links spatial and textual attributes.
  • Georeferencing allows visualization in a more useful, flexible way. Historical maps can be viewed alongside or overlaid on other mapping on line, enabling comparison of maps over time and research into landscape change and the development of places (Kowal and Přida, 2012:287).

Thank you very much for your help!

All 912 maps from the first project phase are georeferenced. In just four months, more than 30 volunteers have identified the maps in GeoPortOst, and set over 23,700 control points.

We would like to thank all the participants for the great commitment and the impressive result.

To all participants: Please contact us (,

  • because your feedback is important for the development of GeoPortOst.
  • because we would like to keep you informed about the project progress,
  • because we want to thank you personally. We would also like to thank the three top contributors Tucker Jones, Robert and Demeter, Gabor by sending you a little gift (GeoPortOst T-shirt, a coffee mug or a large format reprint with a motif of your choice from the collection).


  1. See a video explanation of how it works with examples from the British Library: Video
  2. By clicking the button in the Participate! section (Georeference a Random Map), you will be assigned a map at random. In the application, the historic map will appear on the left; a modern map will appear on the right.
  3. If you are interested in a region or a topic, you can search specifically in the Geoportal. After selecting a map, click the button Georeference this Map under the map image in the main window. This takes you to Georeferencer for your map.
  4. Log on by using email/password (necessary to register upon first use) or social media account (Facebook/Google/Twitter).
  5. Zoom into the old map enough to read it, and then find the corresponding location on the modern map. Use the gazetteer at the top if necessary. Click on the This map tab for more information. In some cases, it may be useful to consult historical gazetteers, which you can access in the Map Guide.
  6. Click on one map to assign a point, then assign a point at the same location on the other map. Look out! Check that the correct points are linked together. Assign as many control points as you can, distributed as much as possible over the entire map.
  7. Define the content area of the map by clipping the borders (see video instructions).
  8. Click the red Save button in the upper right when you are finished. Now, you cam see the overlay of the georeferenced map.
  9. Check the location of the map as overlay, adjust your control points if necessary, add more control points or go on to the next map.

Enjoy and thank you!

Download the Detailed Instruction

Contact Information

For questions/remarks please contact us:

Maps Already Georeferenced

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