### The TRE and RGN files

These files are so inter dependant that it only makes sense to put them into the same package.

#### The TRE file

This file describes the structure of the map. It contains the zoom levels that exist in the map and how the map is divided up.

There are in effect several copies of the map at different levels of detail. Each level is divided up into several areas known as subdivisions. These subdivisions form a tree, with more detailed ones being children of the higher (less detailed) levels.

#### The RGN file

This file contains the detailed location and path of all the map objects. Pointers from the TRE file indicate the start of the definition of a map object and information from the TRE section needs to be used to work out where the location of the map object is.