The science of mapping interstellar space.

The Imperium uses a co-ordinate system of longitude, rays of latitude, and parsecs. Rays of latitude extend from the galactic core, while concentric rings of longitude are placed at one parsec intervals. By convention, the concentric ring passing through Reference ( Core / Core 2118) is labelled the 10,000th ring, and is used as a baseline. Similarly, the ray of latitude extending from the centre of the galaxy through Reference is designated as the first ray. Measurement is in parsecs, counting in the trailing direction. The circumference of the 10,000th ring (r=10,000) is 62,832 parsecs. Counting spinward uses a subtraction from 62,833, which is the equivalent of the zero baseline.

The format for expression of location is: xxxx ring/ray yyyyy, where xxxx is the ring of longitude (distance from the galactic core in parsecs) and yyyyy is the distance of the ray of latitude (in parsecs) from the first ray of latitude, measured along the ring of longitude in the trailing direction. For example, Regina ( Regina / Spinward Marches 1920) is 9930 ring/ray 62723.

This mapping system is highly Imperio-centric, and other systems are used by other peoples and races outside the Imperium. This system has gained wide acceptance, however, among Imperium-dominated client-states, human and otherwise. The system breaks down and is prone to error beyond certain limits. It does serve admirably for a band approximately 400 parsecs wide at a longitude of 10,000 parsecs.

(SUPP-8, 1107)

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