Georeferencing: a second life to old maps

You create a virtual reality by putting an early map on top of a modern one. That's what georeferencing means. In this way you compare old to new situations. The georeferenced map layers show the changes over time. In addition, the old maps can be better analysed and are therefore better suitable for research purposes. By georeferencing Utrecht University Library wants to create perfect access to its collection of early maps for lecturers, researchers and students. The georeferenced maps can be used directly in your own geographical software and the georeferenced maps are easy to find via an interactive world map.

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 (if available; otherwise wait for new projects to come). 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.

Georeference an old map
Compare old maps with each other
Georeferenced old maps

If you want to help the Utrecht University Library georeferencing its historic map collection, it is advisable to create an account at Old Maps Online. Click on one of the web pages of the Old Maps Online 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:

Visit the georeferencing page of Utrecht University Library and click on ‘Georeference an old map’.
If available 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.
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.
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’).
Use the zoom in + or out - button to navigate the maps, or the scroll wheel on your mouse.
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.
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.
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.
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.
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.
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.
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’).
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.
The menu under ‘Layer properties’ also offers turning on (‘Visible’) and off (‘Clipped with cutline’) the map border margin.
From the 'This map > Trace Features > Draw Vectors' window, use the VectorEditor to locate and measure areas, distances, locations, and more. Use the 'Transcribe' feature to annotate the maps.
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.
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.

Digital access to 3,500 maps

A total sum of about 3,500 early maps have been made digitally accessible with the help of georeferencing. This was an extensive project, for which we called in a large audience by means of online crowdsourcing.

Apply georeferencing

What can be done with all these digitised and georeferenced maps? Read this article to learn how lecturers, researchers and students apply georeferencing in their daily practice. Georeferenced maps from the collection of Utrecht University Library are also used by the Utrecht Archives in the application Utrecht in perspectief; an interactive website that combines town profiles, old maps, archival documents and Wikipedia pages via linked data.

Georeferencer

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.

Georeferencer version 4 has two main applications:

the Georeference application with the logo of Utrecht University
the search & compare application Old Maps Online

We will explain these applications in the next paragraphs.

Georeferencing maps in the georeference application

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.

De 'This map'-pagina, met de kaart van Holland door Pieter van den Keere, 1617. — The 'This map' window, with the map of Holland by Pieter van den Keere, 1617.

De 'Georefereer'-pagina, met de kaart van Holland door Pieter van den Keere, 1617. De rode punten zijn de toegekende referentiepunten. — The 'Georeference' window, with the map of Holland by Pieter van den Keere, 1617.

Nauwkeurigheidscontrole door gebruik van 'Coordinates', kaart van Holland door Pieter van den Keere, 1617. De rode cirkels kunnen duiden op onnauwkeurig geplaatste referentiepunten, maar zijn ook vaak het gevolg van onnauwkeurigheid in de oude kaart. — Checking accuracy using 'Coordinates', map of Holland by Pieter van den Keere, 1617.

3D-weergave van een kaart van een deel van de Alpen. — 3D-view of a map of a part of the Alps.

Comparing maps in Old Maps Online

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

Het vergelijkingsscherm van Old Maps Online met een kaart van Holland door Pieter van den Keere, 1617. — The 'Overlay & compare' window in Old Maps Online.

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 1649.

Vier kaarten van Rotterdam uit de periode 1684-heden in de 'Grid'-weergave in Old Maps Online. — Four maps of Rotterdam from 1649 to the present shown in the grid view in Old Maps Online.

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.

Kaart van het Hoogheemraadschap Schieland (detail van Rotterdam), 1684, in de 'Swipe'-weergave van Old Maps Online. — Map of the water control board of Schieland (detail of Rotterdam), 1684, shown in the swipe view in Old Maps Onliner.

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.

Kaart van het Hoogheemraadschap Schieland (detail Rotterdam), 1684, in de 'Spy glass'-weergave van Old Maps Online. — Map of the water control board of Schieland (detail Rotterdam), 1684, shown in the spy glass view in Old Maps Online.

Progress of the most recent project on Blaeu atlases

Top contributors project on Blaeu atlases

Project on maps in the Ackersdijck Collection (finished!)

The georeferencing project on maps in the Ackersdijck Collection was made possible by a generous gift of EGIS (Foundation European Conference on Geographical Information Systems). Jan Ackersdijck (1790-1861) was a Utrecht professor economics and statistics. He set up an own map collection, and used these documents among other for his courses. In 1864 the collection of about 1,500 maps was donated to the Utrecht University Library by his widow. The books and archives of Ackersdijck were also donated to the library.

Progress of georeferencing of all maps

Top contributors all time

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.), which can also be opened full screen for a better performance: