To delete a control point on the georeference toolbar click “Select Link”, click on the control point you want to delete, then click, “Delete Link”. Repeat step four until you have four or more control points on your historical map (Figure 3). Turn your historical map back on and notice how your two maps lined up where you created your control point. To finish creating your first control point click on the same obvious feature on your base map that you selected on your historical map. In the “Table of Contents” turn off your historical map by clicking in the box next to your historical maps name (Figure 2). My choice of obvious features is the corner of Farris St. In this example I am using my fourth control point. Control points will allow your historical image to shift, warp and stretch in order to fit you base map. On your georeferencing toolbar click “Add Control Points” (Figure 1). Start by adding control points to your map.
To add your historical map into ArcMap, click “Add Data (click the plus sign) and route to your work folder, click and add your historical map. Click “Customize→ Toolbars→ Georeferencing” (Figure 1). Step Three: Add your historical map to ArcMap and add the Georeferencing tool to your toolbar.Īdd the Georeferencing tool to your toolbar.
Any base map used in this process should already have a spatial relationship. Now, use the “Zoom In”, “Zoom Out” and “Pan” tool to adjust your map to the desired area of your historical map.
To add your base map, on the toolbar click “Add Data (click arrow) → Add Basemap→ Imagery with Labels” Do that process again but in the Basemap option add “Streets” to ArcMap. To begin, open ArcMap, and when the “Getting Started” menu opens, click “Cancel”. Step Two: Add in and adjust your base map. My images name is “MC 1877 Map Clarksville”. Save the new desired map to a work folder and name it accordingly. Purpose: The “Georeference Tool” gives maps without spatial relationship a reference to base the new map on and use it to replace the old map to better represent you data. Rectification is the process of applying a mathematical transformation to an image so that the result is an image that could be used as a base map.Ĭontrol Points are one of various locations on a paper or digital map that has known coordinates and is used to transform another dataset-spatially coincident but in a different coordinate system-into the coordinate system of the control point. Georeferencing is the process of aligning geographic data to a known coordinate system. Georeferencing Tool – Rectifying an Image