The science of mapping interstellar space. Basic to any science of mapping
is a coordinate system. The scientific system used by the Imperium is based on rings of longitude,
rays of latitude, and parsecs. By convention, rays of latitude and
rings of longitude are measured from a starting point at Reference/Capital,
the world where the data from the First
and Second Imperial Grand Surveys are
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. This mapping 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, which is a region precisely centered on the Imperium.
In ordinary discourse, a world is referred to by its name, sector, and subsector.
For example, the homeworld of Archduke Norris is Regina (Spinward Marches/Regina) that is, the world Regina in
Regina Subsector in Spinward Marches Sector.