- An astrographic hex is located within an idealized yet hypothetical set of 3D coordinate cubes radiating out from the Imperial Encyclopediopolis on Reference (world).
- Encyclopediopolus represents the coordinate location of x: 0, y: 0, and z: 0.
Hexes: Each hex is 3.27 light years across, from each flat edge to the opposite flat edge. Starships can Jump the number of hexes equivalent to the Jump Drive rating of the ship (Jump-1, Jump-2, etc).
- A hex represents a single parsec in the abstract.
- Sectors: Sectors also use an X, Y, and Z coordinate system.
Early Traveller settled on a 2D hex for ease of game play and game aid sheets (...forms). The subsector eventually grew into a 8 x 10 hex map sheet and the display system has stuck ever since.
Fans have experimented with 3D systems with mixed success, over the decades, although using such a system can be tedious and time-consuming. It might just be a better idea for electronic play than old-fashioned paper, pencil and dice-based RPG gameplay.
The system has become very widespread across sci-fi RPG's, many of whom were influenced by Classic Traveller.