Georeferencer compare is an online tool that assigns a geographical location to an image. The website has been created by Klokan Technologies, a Swiss company specialized in online map publishing. Everyone can use Georeferencer compare.
It allows you to overlay historic maps on modern maps (or on other historic maps). It can be used to reveal changes over time and to enable map analysis and discovery.
To compare maps, you can either choose a map from the David Rumsey collection* or use you own map. If you are using you own map, you will have to georeference it.
The procedure to do it is quite simple:
1- Upload your image
2- Georeference it by finding identical points
To georeference your map, you can do it side by side, by overlaying maps, by entering a location’s coordinates or by dragging circle nodes to create a cutline of the area you want to compare.
Screenshot of the georeferencing procedure using the side by side method 20/10/2019.
Once you’re done click on the save button.
3- Compare the maps
The website provides different ways to present your map using interactive visualisations: overlay, compare, swipe, spy glass, grid and 3D view techniques.
Screenshot of the comparing procedure using the spy glass method 20/10/2019.
Screenshot of the comparing procedure using the swipe method 20/10/2019.
With the latest version (v4) you can georeference several maps on one sheet, use the Grid view option to compare multiple maps, use Swipe and Spy Glass views, built in 3D viewer, and Transcribe and GeoEditors options, and all new Georeferencer Compare views options.
You can also export your map for GIS and library catalog: the provided map services are compatible with the Web Map Tile Service (OGC WMTS). High-resolution images are displayed via International Image Interoperability Framework (IIIF).
The individual maps can be exported in a form of GeoTIFF files – which are compatible with amost all geographic information systems (GIS). The library catalog records can be enriched with geographic information improving discoverability of the maps – in a form of MARC 034 or Dublin Core DCMI standards.
*All the maps are from the collector David Rumsey. In 2009, David Rumsey donated more than 150 000 rare maps to Stanford. More than 90 000 of these maps have been numerized and a lot of them can be used on the website.
An article dedicated to his work is available on Veille Carto (link in Sources).