Just posting this as a quick primer on how the numbering system counts up as several people have asked me recently!
Using the sector EAFOTS out by Heart and Soul as an example. I hear it's very popular in Tionisla these days.
In the name we have various different parts:
EAFOTS AB-C D1-2
EAFOTS - the sector name
A - this counts up through the alphabet as the code increases.
B - this counts up through the alphabet as the code increases.
C - this counts up through the alphabet as the code increases.
1 - this counts up as the code increases. (To begin with, this has a value of zero, and is not displayed in the name - see below.)
When I write this number in examples, if it is in brackets, ignore it.
D - the mass-code, this (usually) indicates the mass of the primary star, from A (lightest) to H (heaviest)
2 - this tells us which particular system it is within the subsector.
When the first number in the name is zero, it is omitted from the displayed name, so that instead of seeing:
EAFOTS AA-A A(0)-0
It is simply displayed as:
EAFOTS AA-A A0
This is why systems along the "south" side of a sector will usually have only one number in their name, while systems along the "north" side will usually have both numbers.
The sector names are also procedurally generated with a similar but more complicated code and big lists of phonemes, and a hash function which chooses between single part and two part names. It's horrible. Fortunately we don't need to go there.
Ask CMDR Alot.
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Each sector is a cube 1280ly on each side. For each mass code, the sector is then subdivided into a number of smaller subsectors ("boxels") which are smaller cubes.
For mass code H, there is only one subsector, which takes up the whole sector. This is why mass code H systems are always AA-A H.
For mass code G, there are eight subsectors, cubes of 640ly on each side.
For mass code F, there are sixty-four subsectors, cubes of 320ly on each side.
Right down to mass code A, where there are over 2 million subsectors, cubes of only 10ly on each side.
The numbering system works at this smallest level.
It begins at AA-A A(0)-0 at the "west" "south" "down" corner of the sector.
The next subsector along, one box "east", is BA-A A(0)-0, and the next subsector is CA-A A(0)-0 and so on.
When we get to ZA-A A(0)-0, the next one is AB-A A(0)-0, then BB-A A(0)-0 and so on.
(Similarly when we get to ZZ-A A(0)-0 we move on to AA-B A(0)-0 and when we get to ZZ-Z A(0)-0 we move on to AA-A A1-0. This is the point where the first number starts to be displayed.)
When we get to the end of the row, after 128 boxes, we loop back to a position one subsector "up" from the start, and move along the row above the one we've just done.
We go from XE-A A(0)-0 to YE-A A(0)-0.
When we reach the end of the top row, we loop back right next to where we started, but one row "north".
We go from DG-Y(0)-0 to EG-Y(0)-0.
, and so on right the way through the sector.
The very first possible position is AA-A A(0)-0 and the last is RH-I A119-0.
For the higher mass-codes, the system used is the same, but only a subset of the names are used - the names are given as if they were in the same position as the mass-code A names, so for all mass-codes, the "south" "west" "down" start point wwill *always* be AA-A (mass-code)(0)-0 and the subsector one row "north" of it will *always* be EG-Y (mass-code)(0)-0. And so on...
With thanks to Boogyman - here's a graphic to illustrate the example.
