This project will create a dedicated Atlascope instance for Detroit, enabling public and scholarly engagement with the city’s cartographic history by georeferencing 16 historical atlases and aerial imagery sets and launching a publicly accessible web application in partnership with Wayne State University Libraries, DETROITography, OldInsuranceMaps, and the Boston Public Library (the “Detroit Atlas Collaboration”). Atlascope is a digital mapping platform originally developed by the Leventhal Map and Education Center at the Boston Public Library. It enables users to explore georeferenced historical atlases overlaid on modern basemaps, offering a powerful tool for understanding urban change and historical geography: more about Atlascope.

Georeferencing is the process that embeds geospatial metadata into a historical map, allowing it to be integrated into modern web maps or other GIS software. Users perform this task by creating control points that link the old map with the current map. In order to create the final product in Atlascope individual map tiles will need to be stitched together this way using the open source tool: https://oldinsurancemaps.net/

The first step will be to go to the website and sign up for an account. Once completed you are ready to get started on the section of the map for 1929 found here. 

To get started on the aforementioned section, scroll down to the dropdown menu labelled Prepared. Look for the next tile in the sequence (in this example we will be using Page 80) and click georeference. 

Now you will see the overall interface that will allow you to georeference the historical map. In the right hand panel the Key Map will already be generated and overlayed onto the current map. Transparency of the Key Map can be adjusted with the Reference drop-down menu underneath the map. For each historical map piece you will need to find the corresponding number on the Key Map. In this example case that would be tile 80. 

Once you have located the general area of where the map piece will go you will then need to set the Reference map to None and check the box labelled Parcels. Using the historical map piece on the left hand side you can more specifically find the intersections that match on the present day map on the right.

Note: the Key Map should be used ONLY as a means to help find where pieces go. It is not 100% accurate so streets may be off center a bit. 

In this case we can clearly see the main streets match up with the exception of Continental St., which has been removed over time. Now we can set our control points for the old map on the present day map. It is best to set 3-4 points, keeping in mind that they should be spread out as much as possible to ensure everything aligns correctly. The best way to keep things accurate is to use the corner of intersections with land parcels. As you can see in the next image we used the corner of the land parcel at the intersections of Freud St and Navahoe St.

To set each control point you will need to click on the historical map on the left first and then place the corresponding X on the current map on the right. Below you can see how it should look once all the points have been set in the corners of the land parcels. 

Note: if you cannot find appropriate land parcels then consider skipping to a different map piece or asking staff for assistance. 

By using the Preview dropdown you can see a preview of what the map looks like over the current map to check for accuracy. Note: not all maps will be a direct 1:1 as neighborhoods have changed over time. But in this instance everything matches up smoothly. To complete georeferencing click on the check mark in the upper right portion of the map window. The system will georeference the map and take you back to the previous landing page to do the same process over for the next piece!