Because maps can be created in a number of different projections and varying degrees of accuracy, the landmasses, countries, bodies of water, roads etc. may not exactly match up between any two maps. In order to counteract this problem, a number of tools exist that allow you to warp (also known as rectify or georeference) a map, so that it will fit on a Google Map or another mapping applications's interface. The resulting warped map should then be easier to work on using that application.
| Application | Description | Benefits | Drawbacks | Tutorial |
| Google Earth Overlays |
Putting a historical maps on Google Earth is very simple. It is simply laying the map image over a section of the globe on Google Earth, then resizing the map image so that it lines up with the features on the globe. Unlike the other tools in this section there is no stretching involved. Because of this, it is very difficult to get a perfect match unless you're mapping a small area and the map is drawn to scale. Learning curve: Incredibly simple to use, but hard to get precision. |
Quick |
Requires Google Earth Software Cannot warp maps, can only resize and rotate maps Usually not very accurate |
Google Earth Tutorial |
| WorldMap WARP |
WorldMap WARP is an online tool to rectify an uploaded map so that it may fit exactly(or more closely) on a modern precise map, such as a Google map. While rectifying maps, WorldMap WARP also geo-references the uploaded map on an online modern map, so that physical landmarks(coasts, streets, geological features, etc.) will lay ontop of each other. Similar in design to NYPL Map Warper and Map Warper, however this tool seems to be no longer maintained. It is at its best when you're just trying to warp a map to an area so that you can download the rectified PNG or TIFF or store it for later use, or if you want to use the the warped map's "tiles base URL" in other tools. You can use its "Tiles base URL", but you need to add curly brackets(i.e. { }) around the "x", "y", and "z". Basically this is the same tool as Map Warper except it is less maintained and the maps can be made private. Learning curve: Warping a map is fairly intuitive. Other features require more guidance (exporting the map is not very intuitive), and the fact that the tool appears to be no longer maintained makes some the tool slightly harder to work with. |
Any map (in XYZ format) can be warped Can add metadata to the maps Can be set to public or private Can be done on any computer/web based; Can export an image of the rectified map as a PNG or a TIFF, as a KML file, or a WMS URL Keeps a record of the edits made to the map Can be edited by multiple people for collaborative purposes |
Not always the most accurate The cropping section of the site no longer appears to work |
WorldMap WARP Tutorial |
| Map Warper |
Map Warper is an online tool to rectify an uploaded map so that it may fit exactly(or more closely) on a modern precise map, such as a Google map. While rectifying maps, Map Warper also geo-references the uploaded map on an online modern map, so that physical landmarks(coasts, streets, geological features, etc.) will lay ontop of each other.
Similar in design to WorldMap WARP and NYPL Map Warper. It is at its best when you have a map that cannot be warped onNYPL Map Warper or David Rumsey Georeferencer and you want to collaborate with others or work from any computer when rectifying the map, or if you want to use the the warped map's "tiles base URL" in other tools. Basically this is the same tool as Harvard's WorldMap WARP except it is more maintained and the maps cannot be made private. Learning curve: Warping a map is fairly intuitive. Other features require more guidance(exporting the map is not very intuitive). |
Any map (in XYZ format) can be warped Can add metadata to the maps Can be done on any computer/web based; Can export an image of the rectified map as a PNG or a TIFF, as a KML file, or a WMS URL. Keeps a record of the edits made to the map Can be edited by multiple people for collaborative purposes |
Not always the most accurate Edits can only be set to public, so everyone can see the edits |
Map Warper Tutorial |
| NYPL Map Warper |
NYPL Map Warper is an online tool to rectify a map so that it may fit exactly(or more closely) on a modern precise map, such as a Google map. While rectifying maps, NYPL Map Warper also geo-references the chosen map on an online modern map, so that physical landmarks(coasts, streets, geological features, etc.) will lay ontop of each other.
Similar in design to WorldMap WARP and Map Warper. It is at its best when you've found a map from the NYPL Digital Collections and you want to collaborate with others or work from any computer when rectifying the map, or if you want to use the the warped map's "tiles base URL" in other tools. Basically this is the same tool as WorldMap WARP and Map Warper except it will only work for maps from NYPL Digital Collections. Learning curve: Warping a map is fairly intuitive. Other features require more guidance(exporting the map is not very intuitive). |
Can add metadata to the maps Can be done on any computer/web based; Can export an image of the rectified map as a PNG or a TIFF, as a KML file, or a WMS URL Keeps a record of the edits made to the map Can be edited by multiple people for collaborative purposes Can crop edges of the map so that only geographic information is warped |
Can only warp select maps from the NYPL Digital Collections Not always the most accurate Edits can only be set to public, so everyone can see the edits |
NYPL Map Warper |
| David Rumsey Georeferencer |
The David Rumsey Georeferencer is an is an online tool to rectify a map so that it may fit exactly(or more closely) on a modern precise map, such as a Google map. While rectifying maps, David Rumsey Georeferencer also geo-references the chosen map on an online modern map, so that physical landmarks(coasts, streets, geological features, etc.) will lay ontop of each other. It is at its best when you've found a map in the David Rumsey Map Collection and you want to collaborate with others or work from any computer when rectifying the map. Learning curve: Sometimes it can be frustrating to find a map on David Rumsey that is available to be georeferenced. Otherwise the tool is fairly intuitive, and there is a guide to explain the features that aren't. |
Simple and easy to use design Easily see two warped maps layered on top of each other Fast warping |
Can only warp select maps from the David Rumsey Map Collection Edits can only be set to public, so everyone can see the edits |
David Rumsey Georeferencer Tutorial |
| Map Tiler |
Map Tiler is a tool to rectifiy a map so that it may fit exactly(or more closely) on a modern precise map, such as a Google map. arper also geo-references the selected map on an online modern map, so that physical landmarks(coasts, streets, geological features, etc.) will lay ontop of each other. This tool unlike most of the other tools in the page is not an online tool. It uses online maps to rectify your map, but you must have your own map as a file on the computer you're using. Map Tiler is at its best when you have a map on your computer and you want it to predict where the points will be or you want to get very technical. Learning curve: Rectifying the map is simple, especially since it predicts points. Exporting the map and then hosting so that you can share it is complicated. The Map Tiler website offers a How-to section, which should help with most features. |
Automatically predicts points you select with increasing accuracy, after you've added 2 points. Has an associated iOS and Android app that allows you to view the rectified maps. |
Map Tiler software must be downloaded and installed to use Associated iOS/Android app is not free. Once a map has been rectified, it cannot be re-rectified; you must start the project again. Leaves watermarks on the map, in the basic version |
Map Tiler Tutorial |
Created using Map Tiler
Taylor, A. Merritt. Tentative Location of Future Rapid Transit Lines. In: Taylor, A. Merritt. Report of transit commissioner, city of Philadelphia, July, 1913 Vol. 2. Philadelphia: City of Philadelphia, 1913, Map No. 45.
