Georeference

In order to display raster images with other spatial data, you first need to align or georeference those images to a map coordinate system. When you georeference a raster image, you assign real-world map coordinates so that it can be viewed and queried alongside other spatial data. The process involves the specification of a series of control points that can be used to link points on the raster image with locations in a spatially referenced dataset.

In general, the wider the distribution of control points across the image (and the better the overlap between the raster image and the referenced dataset) the better the results.

The application uses control points to calculate the best georeferencing solution by means of a least squares adjustment. It does not, however, rectify any distortion within the image. If your image contains distortion, such as a fold or crease in a scanned map, or the topographic distortion associated with air photos of mountainous terrain, you must remove this distortion using image processing software before displaying it in the application.