Plot Files (".PLT")

When cavers survey a cave, the measurements are in what is called "polar" coordinates. However, computers generally use "Cartesian" coordinates to display images. For this reason, the main job of the compiler is to convert polar coordinates to Cartesian coordinates.

With polar coordinates, you measure angles and distances. For example, with the typical survey shot, you measure a compass angle, a distance and an inclination. Cartesian coordinates on the other hand measure the distance from the entrance in the East, North and Vertical directions. For example, a station might be 25 meters north, -17 east and -35 vertical from the entrance.

When the compiler generates Cartesian coordinates it writes them to a special file called a Plot File. By saving coordinate information in a special file, Compass saves memory, and speeds up viewing and plotting caves. Plot files have the extension ".PLT" or ".PLF" for special feature files. Plot files can be viewed, printed and manipulated in a variety of ways. For example, the Project Manager will automatically display plot files for you. You can, however, view a plot file manually using the Compass Viewer.