Overlay layers generally consist of external GIS data that provide additional information or context. Overlays can't be edited or changed, so they serve as static background data. CSDatum staff can add almost any GIS data to the software, and once added, it can be turned on and off from the Overlay menu.

The list of overlays that can be added to the map could be extensive. To find the appropriate overlay, scroll through the list or use the search box at the top of the menu. Typing into the search box immediately filters the list of overlays based on the word entered.

Click on the chosen overlay to turn it on and add it to the map.

When an overlay is added to the map, the layers of data are displayed in a specific order. This order will affect which data can be seen on the map. Map data is layered as follows:

The order of the layers may cause some lower level layers to be obscured by higher level layers. For example: an overlay aerial photo will totally obscure the roads and terrain shown on the Base Layer map.

In addition, the order that you turn on the overlays affects visibility. Each new overlay that is turned on is layered over top of the previous overlays.