Georeferencing allows you to overlay historic maps on modern maps or other historic maps. The overlaid maps reveal changes over time and enable map analysis and discovery. With georeferencing Utrecht University Library wants to give especially research and education optimum access to its collection of old maps.

For georeferencing use is made of the innovative software of Georeferencer, version 4. Features in this version include various viewing possibilities (Overlay, Grid view to compare multiple maps, Swipe, Spy Glass, and built in 3D viewer), Transcribe and GeoEditors, and the availability of georeferenced files for re-use in own GIS applications.

People with interest in history and maps can help georeferencing the Utrecht University Library collection of old maps, by clicking on the 'Fix the location of a map' link below. Users who georeference the most maps will be recognized in the bar displays below. Recently georeferenced maps can be viewed by image or by location.

N.B. Best viewed in Chrome and Firefox.

How to start? Fix the location of a map Georeferenced maps Compare maps

About the use of Georeferencer

Georeferencer version 4 has two main windows:

Consecutively, these windows will be explaind below.

Georeferencing maps in ‘This map/Georeference' window

This window allows you to georeference maps, view maps in 2D and 3D, geoedit maps, get map links for GIS apps, transcribe annotations on the maps, and more.

The 'This map' window, with the map of Holland by Pieter van den Keere, 1617.

The 'Georeference' window, with the map of Holland by Pieter van den Keere, 1617.

Checking accuracy using 'Coordinates', map of Holland by Pieter van den Keere, 1617.

3D-view of a map of a part of the Alps and Po Valley, 1803.

Comparing maps in ‘Overlay & compare' window

This window allows searching for maps from various sources, then comparing them using several different views: Overlay, Grid, Swipe, and Spy glass.

The 'Overlay & compare' window.

The Georeferencer 'Overlay & compare' page below shows a grid view of four maps of the environment of Rotterdam made at different times from the present back to 1684.

Four maps of Rotterdam from 1684 to the present shown in the grid view in Georeferencer.

The Georeferencer 'Overlay & compare' page below shows a swipe view of two maps of the environment of Rotterdam - the present day map and the 1684 map.

Map of the water control board of Schieland (detail of Rotterdam), 1684, shown in the swipe view in Georeferencer.

The Georeferencer 'Overlay & compare' page below shows a spy glass view of two maps of Rotterdam and surroundings - the present day map and the 1684 map.

Map of the water control board of Schieland (detail Rotterdam), 1684, shown in the spy glass view in Georeferencer.

How to start?

If you want to help the Utrecht University Library georeferencing its historic map collection, it is advisable to create an account at Georeferencer. Click on one of the web pages of the Georeferencer application top right on ‘Sign in’. Once signed in, you can enjoy all functionalities of the application. There are a lot of help screens that show the process of georeferencing the maps as you move through the steps.

The steps of georeferencing are as follows:

  1. Visit the georeferencing page of Utrecht University Library and click on ‘Fix the location of a map’.
  2. A random map will open on the right side window with a modern map in the left side window. For more information about the map, click on the 'This map' tab.
  3. There are several choices of modern maps to use, click on the upper left globe symbol (‘Change the base map’) to choose the best one for the area in question.
  4. If the historic map location is not clear, find the name of a town or street and search on that term in the modern map search window (‘Find a place’).
  5. Use the zoom in + or out - button to navigate the maps, or the scroll wheel on your mouse.
  6. Find common locations on the old and modern maps and place sets of points on each. Three points are the minimum required, but more than three points will increase accuracy.
  7. Spread the points as evenly as you can across the maps for better results. Try to extend points to the map margins. If you make a mistake with any point, mouse over a point and hit delete, then re-position the point and click on the map until the points number shows.
  8. Use the 'Overlay' and 'Coordinates' tabs to detect errors. Remember that very old maps may have inaccuracies in the original cartography and understanding the degree of these inaccuracies is one of the things that Georeferencer makes possible.
  9. When you are finished placing points, use the 'Clip' tool to crop the map just inside the map border. This will make the map blend more easily at the edges with the modern map and also define the area of the map's coverage in our database.
  10. Click on the 'Save' button and the map can be viewed in the 'This map' window and the 'Overlay & compare' window. If you have not logged in you will be asked to; setting up an account is free. In the 'This map' window you can view the historic map in 2D or in 3D  or using the side-by-side viewer in the Georeferencer 'Overlay & compare' window. Maps that show mountains and other elevated areas will use the built in DEMs (Digital Elevation Models) in the 3D viewer  to show those areas in three dimensions.
  11. In the 'Overlay & compare' window you can view one map or search for maps from various collections, and then compare them using several different views: overlay, grid, swipe, and spy glass. You can combine and compare maps from many other libraries using the Old Maps Online tab (‘All maps’) in the 'Overlay & compare' window along with maps from our collection. You will also be able to upload your own maps and georeference them. Those maps will then show up in your 'My private maps' list.
  12. If the map needs correction or refinement of points, sign in and click on the Georeference tab in the 'This map' window and you can add or correct points. To get to the Georeference tab if you are in the 'Overlay & compare' window, just click on the name of the map in the upper right box or on the symbol of the pencil (‘Edit georeference’).
  13. Polynomial and TPS views (via ‘Layer properties’) of the map use more complicated calculations to render the map and may result in more accurate renderings, but they will require more points to be made and they may distort the shape of the map. The default view is Affine, which will stretch the map but not alter its shape.
  14. The menu under ‘Layer properties’ also offers turning on (‘Visible’) and off (‘Clipped with cutline’) the map border margin.
  15. From the 'This map' window, use the GeoEditor to locate and measure areas, distances, locations, and more. Use the 'Transcribe' feature to annotate the maps.
  16. More experienced users will be able to export the georeferenced map using the  Use in GIS apps - 'Get links'  in the lower left of the 'This map' window. This will enable viewing the maps in various GIS web based and desktop programs.
  17. If you find bugs or problems, use the Hamburger drop down menu in the upper left corner of all screens to send us a message about the problem with the 'Send feedback' tab.

Klokan Technologies developed Georeferencer with the Moravian Library.

Progress of the recent project on maps of the Netherlands and Dutch regions

Progress of georeferencing of all maps

Top contributors and charts all time

Top contributors past month

Recently georeferenced maps

Search engine

All georeferenced maps of the Utrecht University Library are accessible through a powerful search engine (search for key words, scale, timeline etc.):

The website of Old Maps Online also gives access via a geographical interface to thousands of scans of cartographical documents, belonging to the collections of several other libraries and institutions. 

Georeferenced map finder