Georeferencing and Editing Data

The term "georeferencing" may not mean much to most people, but it's a pretty important concept for those of us working with GIS.  Aerial photos, images of the earth's surface taken remotely, can really only be of use in GIS if they are an accurate spatial representation- otherwise they're really just photos.  These raster images can be lined up with an accurate map using control points, and linking places on the aerial photo with places on the map, and thereby stretching and warping the raster graphic as necessary to be spatially correct. 

The aerial images on the left side, the north and south portions of the UWF campus, were georeferenced to a vector base map of campus buildings and roads.  The text in the upper left corner of the northern photo, and the lower left corner of the south, details the root mean square error of the polynomial transformation.  This measure can be lowered by manipulating the control points used to align the aerial photo with the accurate map.  Control points create a more accurate transformation when they are placed as far from one another, and in as many different portions of the map as possible.  The 2 labeled features- the campus gym and Campus Lane- are edits, added to their respective vector dataset feature classes by the addition of a polygon and a line.  These differ from a simple polygon and line drawn on the map in that they are spatially referenced, and their shapes and attributes are actually added to the datasets permanently.  The eagle nest location on the right has 2 buffer zones added around it, which represent a conservation easement around the point feature.