The overlay map viewer, Geo-Enabled Map Viewer, is used to layer the selected maps over each other to see changes over time, examine the historic sheets over a few modern base layers (i.e. Google's street, satellite, and hybrid views), travel around a neighborhood and use historic Sanborn maps as a guide, find other historic Sanborn's relevant to their current search, and much more!
To access the Geo-Enabled Map Viewer a user must either conduct an Address or Latitude/Longitude Search or perform a Browse. Once search results are displayed and at least one search result checked, the View Maps button will take the user into the Geo-Enabled Map Viewer. This information can also be found in the Help tab of your library's subscription when logged in to the database.
Once inside the Geo-Enabled Map Viewer a user can do the following:
- Change the Base Layer Type: Google's base layers are incorporated into the Geo-Enabled Map Viewer. This means that users can change the modern depiction (layer) depending on the type of analysis they are doing with the historic Sanborn map sheets. Google Street View is a base layer, much like a typical road map, that shows streets, buildings, and city plots. Street View is good for identifying and matching streets, highways, major landmarks, and green spaces. Google Satellite is a base layer that offers users a "real-life" birds-eye view depiction of streets, highways, major landmarks, and green spaces. Satellite brings geographic locations to life, allowing users to view a location as if they were there in person, complete with color and multi-dimensional views. Google Hybrid brings the Street View and Satellite View together so that both "real-life" depictions and the road map are joined offering the user the one of the most complete views of a geographic location.
- Add/Remove historic Sanborn maps to the Base Layer: in addition to selecting a Google Base Layer, Geo-Enabled Sanborn Map user can also select which historic Sanborn sheets they wish to view over the modern base layer. Simply select Sanborn map sheet from the right tool bar to view a sheet on the Google Base Layer.
- Adjust the Zoom for the entire Geo-Enabled Map Viewer: use the Zoom bar within the Geo-Enabled Viewer to adjust how "close" or how "far away" you view a geographic location.
- Adjust the Transparency of each historic Sanborn map layer: the transparency of each historic Sanborn map sheet can be adjusted once it has been check-boxed and appears on the base layer. To adjust the transparency of the map sheet slowly slide the transparency bar from 100% (completely solid) towards 0% (completely see through). Setting the transparency close to 50% is a good place to start because both the historic Sanborn map layer and the Base layer are visible. As you add more historic Sanborn map layers to the Base layer the user may find it helpful to adjust the transparency of each historic Sanborn layer so that subtle structural changes become visible.