The standard astronomical unit of stellar cartography is known as the “Sector”. Sectors are cube shaped regions of space, twenty five light years across. Sectors may be grouped together into “Stellar Grids” which are collective groups of twenty seven sectors.
Sectors are designated by numbers; the Federation Sector System begins at Sector 001 (encompassing Earth) and expanding numerical upwards.
Right: Space Sector (25 LYs)
Sectors also may be named by an important system within the Sector, such as the “Kalendra Sector” or the “Bajor Sector”.
Sectors are often used to define political boundaries, but are not in themselves political units. The term “disputed sector” is often used to describe a sector which encompass the borders of two different space powers.
Left: Stellar Grid (75 LYs)
Relative space navigation consists of a series of mathematical equations which calculates the relative distance between a point of origin and destination.
Plotting the relative course of a space vessel begins by identifying a destination relative to the point of origin (the vessel itself). There are two axis to consider - a 360 horizontal "compass rose" encircling the space vessel, and a 180 degree vertical axis, known as the "mark axis".
Above: Horizontal Axis
Once a destination has been identified relative to a space vessel, the vessel is orientated on a "course heading" to place the vessel directly aimed at the destination.
Right: Vertical Axis
At this point, the vessel is said to be "on course" and engages its engines. Enroute to the vessel's destination, minor course corrections are automatically plotted to take into account gravity phenomena, stellar drift, and effects of time dilation at warp.
Relative space navigation is typically only effective for either sub-light distances or for distances no greater than five light years. Astrogation navigation (see below) is used for greater interstellar distances.
Astrogation navigation is a much more complicated method of space navigation which is used to calculate courses over large interstellar distances. In astrogation navigation, a space vessel first determines its galactic position through the use of at least three navigational reference points, usually significant stars or other spacial bodies.
Right: Space Astrogation Compass Wheel
Through the use of a space instrument known as an "astrogator", a course is then plotted relative to the galactic center of the Milky Way - for instance a direct course towards the center of the galaxy would constitute of course of "000 mark 0". Elevation and deviation from this baseline is then calculated, providing an astrogated reference course which is then use to plot the space vessel to its final destination.
Courses determined by astrogation are often referred to as a "True Course" ,in comparison to a "Relative Course" which calculated using relative distance navigation (see above).
Galactic coordinates are a simplified method of space navigation in which a spatial body, such as a moon or planet, are provided with three distinct series of four digit number codes; these serve to identify the stellar location of an object on an X-Y-Z galactic axis.
Galactic coordinates may be feed into a space vessel's navigation computer which then automatically calculates the necessary course and speed to reach a destination in a given amount of time.
This method of simplified space navigation is often used onboard ships with minimal crews, or onboard single person long range craft where the manual calculation of a space heading would be beyond the abilities of a single pilot.