Allmaps

Allmaps is an open-source software ecosystem that makes it easier and more fun to georeference maps. It uses WebGL and the IIIF protocol to overlay maps entirely in a web browser—no software download necessary.

Allmaps is based on the georeference annotation, a JSON-based metadata format that stores all the information required to georeference a map.

There are two main applications in the Allmaps software ecosystem:

• Use Allmaps Editor to georeference maps
• Use Allmaps Viewer to view georeferenced maps

Using this side-by-side app

This tool, built with Glitch, uses the Allmaps Leaflet Plugin to load georeferenced maps and compare them side by side. To compare one georeferenced map against another, simply paste the georeference annotation of a map.

Any map that has been georeferenced using Allmaps has a georeference annotation. You can find it by loading a IIIF-compliant map in Allmaps Editor, clicking the button, as seen in the screenshot below:

Then, paste the annotation—the value of "id"—in the left- or right-hand input boxes of this app and click Load!