Tics Tics A tic is a registration or geographic control point for a coverage. Tics are very important for registering map sheets during digitizing and editing.
Most geographic data is compiled and automated from a series of map sheets or aerial photographs.
Maps are mounted on a digitizer or scanner one sheet at a time and digitized. Aerial photos are mounted in pairs in a stereoplotter. The next step is to transform the coordinates of all input sources into a single common coordinate system. Tics play an important role in map registration for these purposes. Although each coverage contains tics, it is important to recognize that all of the coverages in a GIS database should use the same tics.