Wednesday, February 11, 2015

The Vintage Maps of San Francisco

Last month I posted about how you can create interactive maps from the historical maps in the New York Public Library map collection. Thanks to the library's Map Warper project over 10,000 historical maps have now been georectified and can therefore be overlaid on a modern interactive map.

Today I discovered that the amazing David Rumsey Map Collection also has a project to georectify the thousands of vintage maps in the David Rumsey online map library.

I've therefore been busy searching the David Rumsey Map Collection for vintage San Francisco maps which have already been georectified. I then created a Leaflet map which allows you to browse all the historical maps I discovered. The result is Vintage Maps of San Francisco.

The David Rumsey Georeferencer can be used to overlay any static map on top of a modern interactive map. The georeferencer can also obviously be used to georeference any of the vintage maps in the David Rumsey online map library.

After maps have been georectified using the georeferencer they can then be displayed using an interactive mapping library by linking to the created maps tiles. To grab the URL to the map tile scheme of a particular vintage map you need to first find the map in the collection. For example here is the page you get after searching the David Rumsey Map Collection for 'San Francisco'. The results show vintage maps of San Francisco in the collection.

You now need to click on the vintage map you wish to use in your interactive map. When the map opens if the map has been georectified there will be an orange 'View in Georeferencer' link above the map. Click that link and you will then be taken to a page showing the vintage map overlaid on top of a Google Map. To get the map tiles of the vintage map you now need to click on the 'Embed OGC WMTS tiles' link.

After this you are presented with a choice of three different map transformations. Select the map transformation which you require and you will be taken to a new page which will allow you to view your vintage map overlaid on your choice of interactive map library.

At this point you can simply choose your favorite map library and copy & paste the JavaScript code to create a map. You also have the choice to embed a map by selecting the iframe code for your map. However, if you want to create your own map from scratch, you can also select to view the source code for any of the map libraries and cut & paste the URL scheme for your vintage map tile scheme.

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