Our Georeferencer tool lets you compare old maps with the latest maps. It's good fun and easy to use.
Here, you'll find an outline on how to get started with the Georeferencer. If you want more help, please read our detailed British Library Georeferencer instructions (PDF format, 2 MB).
Step 1: Sign in
Go to http://britishlibrary.georeferencer.com/start
Click Sign in (See top right hand part of the page)
You will be asked to log in. An account with Georeferencer is free and the 'Sign in with email' option only requires inputting your e-mail address, adding a username and password and then confirming through your email. Alternatively, you may login using an existing account with Facebook, Google, or Twitter.
Once you have signed up you will be taken back to the main page.
Click Fix the location of a map button to get started!
Step 2: Start georeferencing
You will be presented with two map boxes in the Georeference tab (see below); the scanned historic map will appear on the right, with a modern map on the left.
The modern map will be Side by side with the historic map.
Examine the maps carefully looking to identify spatial relationships. When a location can be identified on both maps, click on that point on one map, followed by the other. You can use the magnifying glass tool to refine the position by clicking and dragging the cross hairs. If you wish to delete a set of points, finish assigning the pair then select the points by clicking on either with the mouse and press the “Delete” button on your keyboard.
The features that are easiest to identify to make links between historic and modern maps are often road junctions as these frequently have not changed since the map’s creation, while watercourses, house/farm names and boundaries of woods and fields have sometimes altered over time.
If you are struggling to identify the geographical area that the map depicts, try clicking on ‘This map’. This tab contains information about the map and might provide some clues. You can also try using the search tool, made available by clicking on the magnifying glass on the left of the modern map. Try typing a place name that you find on the old map into the search tool and the modern map will move to that location.
Assign as many points as you can over the entire map. The minimum is number is five but more points, spread evenly and extending to the margins, will provide more accurate georeferencing and therefore much more valuable data.
When finished, click the “Save” button to the bottom right of the map.
The thank you dialog box will appear. Click View this map. to be taken to the View tab, showing the historic map overlaid over the modern map.
Step 3: Clip
It is now time to remove the border of the map, what we call clipping.
Click back to the Georeference tab, towards the top left.
Click on the clip selector as shown here:
Follow the ‘Clipping the map’ instructions on the right of the page identify the area of the image that contains the map. Remove the border by clicking on the corners and dragging them.
Congratulations, you have georeferenced your first map! Go back to the bottom right corner and click the ‘Next’ button to return the next map to Georeference.
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