Astrography: The science of mapping interstellar space.
Basic to any science of mapping is a coordinate system. The
system used by the Imperium is based on rings of latitude,
rays of longitude, and parsecs.

Rays of longitude extend from the galactic core, while
concentric rings of latitude are placed at one parsec
intervals. By convention, the concentric ring passing through
Reference/Capital is labelled the 10,000th ring, and is used
as a baseline. Similarly, the ray of longitude extending from
the center of the Galaxy through Reference/Capital is
designated as the first ray. Measurement is in parsecs,
counting in the trailing direction. Computation reveals that
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.

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

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.

(reproduced by permission of the author, Chuck Kallenbach II)
