Use the swipe feature to compare a map of Whitechapel in 1899 with today. We’ve also created an interactive index to make it easy to find streets and locations that no longer exist.
So, for example, if you find out from the 1901 census that your ancestors were living in Pelham Street, Spitalfields, you can find that historic road in seconds with this map, whereas a search on Google Maps would confusingly take you off to a completely different Pelham Street in modern South Kensington. Having identified the old location of east London’s Pelham Street on our map, you can then swipe to see that Woodseer Street today follows the line of Pelham Street from 120 years ago.
To create this dynamic map we used a process called georeferencing to help us marry up a photo of the old map with the modern web map. A Photoshop plugin called Geographic Imager made by Avenza Software helps us to calculate where points on the image correspond to digital coordinates in the real world, typically at the junctions of streets that still exist. After manipulating and reprojecting the image to match the projection of web maps (a projection called web mercator or pseudo-mercator WGS 84 / EPSG:3857), we then uploaded to Mapbox to overlay a modern street map and check how it looks. We went through this process six times manipulating different parts of the image with different settings until we had the overlay working as wanted.
We then imported two maps to a full web page: one with the historic overlay and one without, and used a javascript swipe compare that lets you view both at the same time.
To build the historic location finder we literally plotted a digital point on each street and landmark seen in the 1899 map. In Mapbox each point is automatically given digital latitude and longitude coordinates. We then downloaded all the point labels and coordinates in a format called geojson. The geojson file was then uploaded to the website alongside an html file with coding that calls in the locations for the listings tied to coordinates on the map.
A view of street name plotting in Mapbox
The overlay isn’t perfect, especially as the image of the paper map undulates, but the final result is a decent approximation for a Then and Now map, with – we hope you agree – a very useful historic location finder.