What is Allmaps?

Allmaps is a lightweight open-source software ecosystem that makes georeferencing map collections simpler, easier, and more fun. You can use Allmaps to overlay maps on top of one another entirely in a web browser, without downloading any software or large image files.

Allmaps consists of two main applications: Allmaps Editor and Allmaps Viewer. You can use Editor to georeference maps and use Viewer to display them.

How it works

Allmaps loads maps with the The IIIF protocol, a widely used framework for sharing deeply-zoomable, high-resolution images on the web. By loading maps that already exist on IIIF servers, Allmaps bypasses the computationally intensive and time-consuming steps of downloading and processing large image files (like TIFFs and GeoTIFFs).

Allmaps is built in Svelte and TailwindCSS, and uses IIIF, WebGL, and OpenLayers to dynamically warp maps in the browser. See the GitHub repository for a full description of the Allmaps codebase.

Georeference annotations

Georeference annotations make the magic happen. These lightweight JSON files contain all the information needed to georeference a map, including:

masks, which specify the parts of a map that should be displayed

control points, which correspond pixels in a map image with geographic coordinates in the real world

Georeference annotations are an approved data standard and conform to the Web Annotation Data Model. Check out a sample georeference annotation for this map:

{
  "type": "AnnotationPage",
  "@context": "http://www.w3.org/ns/anno.jsonld",
  "items": [
    {
      "id": "https://annotations.allmaps.org/maps/c26a8031255516aa",
      "type": "Annotation",
      "@context": [
        "http://iiif.io/api/extension/georef/1/context.json",
        "http://iiif.io/api/presentation/3/context.json"
      ],
      "created": "2024-06-25T14:12:18.596Z",
      "modified": "2024-06-25T14:12:18.596Z",
      "motivation": "georeferencing",
      "target": {
        "type": "SpecificResource",
        "source": {
          "id": "https://iiif.digitalcommonwealth.org/iiif/2/commonwealth:3f463c23b",
          "type": "ImageService2",
          "height": 5955,
          "width": 7707,
          "partOf": [
            {
              "id": "https://ark.digitalcommonwealth.org/ark:/50959/3f463198b/canvas/3f463c23b",
              "type": "Canvas",
              "label": {
                "none": [
                  "image 1"
                ]
              },
              "partOf": [
                {
                  "id": "https://ark.digitalcommonwealth.org/ark:/50959/3f463198b/manifest",
                  "type": "Manifest",
                  "label": {
                    "none": [
                      "Boston"
                    ]
                  }
                }
              ]
            }
          ]
        },
        "selector": {
          "type": "SvgSelector",
          "value": "<svg width=\"7707\" height=\"5955\"><polygon points=\"310,276 2603,254 4928,281 7430,285 7388,5801 5193,5713 2143,5749 268,5738\" /></svg>"
        }
      },
      "body": {
        "type": "FeatureCollection",
        "transformation": {
          "type": "polynomial",
          "options": {
            "order": 1
          }
        },
        "features": [
          {
            "type": "Feature",
            "properties": {
              "resourceCoords": [
                1568,
                1078.5
              ]
            },
            "geometry": {
              "type": "Point",
              "coordinates": [
                -71.0798495745,
                42.3710301214
              ]
            }
          },
          {
            "type": "Feature",
            "properties": {
              "resourceCoords": [
                5287,
                701.25
              ]
            },
            "geometry": {
              "type": "Point",
              "coordinates": [
                -71.0379159187,
                42.3790947392
              ]
            }
          },
          {
            "type": "Feature",
            "properties": {
              "resourceCoords": [
                1305.75,
                4525
              ]
            },
            "geometry": {
              "type": "Point",
              "coordinates": [
                -71.0765129065,
                42.3413227921
              ]
            }
          },
          {
            "type": "Feature",
            "properties": {
              "resourceCoords": [
                2729.5,
                2794.5
              ]
            },
            "geometry": {
              "type": "Point",
              "coordinates": [
                -71.0631984209,
                42.3577202471
              ]
            }
          },
          {
            "type": "Feature",
            "properties": {
              "resourceCoords": [
                3486.25,
                5010
              ]
            },
            "geometry": {
              "type": "Point",
              "coordinates": [
                -71.0508495306,
                42.3387771556
              ]
            }
          }
        ],
        "_allmaps": {
          "id": "https://annotations.allmaps.org/maps/c26a8031255516aa",
          "version": "https://annotations.allmaps.org/maps/c26a8031255516aa@6ffbc0e86518e599",
          "image": {
            "id": "https://annotations.allmaps.org/images/4b50c272cb45ca0f",
            "version": "https://annotations.allmaps.org/images/4b50c272cb45ca0f@2ae29dbea23ca2da",
            "canvases": [
              {
                "id": "https://annotations.allmaps.org/canvases/fc306a4ebfecb14f",
                "manifests": [
                  {
                    "id": "https://annotations.allmaps.org/manifests/cfb327e4b43395e3"
                  }
                ]
              }
            ]
          },
          "scale": 1.034986,
          "area": 36360362.94
        }
      }
    }
  ]
}

Allmaps tools and experiments

Core Allmaps tools:

Allmaps experiments: