They can be used for competitions so that every competitor starts with the same world, just as you do with a scenario.
Length and valueEdit
The following slightly edited quotation from User blog:Enojado271/Imp 2 Map Gen Keys: In Summary notes that the characters in the key combine to produce any one of quintillions of possible maps:
- Every map key has two parts, a value and a length. Every key with the same value and length produces the same map (with a few exceptions, as noted below).
- The length is simply the number of characters in the key.
- To calculate the value:
- Convert all the characters to their ASCII decimal values, which you can find under the column "Dec" in ASCII#ASCII_printable_characters
- Multiply each character's value by 2^(n-1) where n is the position of the character, counting from right to left. (In other words: do nothing to the rightmost character. Double the next one to the left. Multiply the next one left by 4, then 8, 16, 32, etc.)
- Sum all these products for the map key's value.
A table to help calculation is on the Value page.
By changing characters you can make another key that usually produces the same map because it has the same length and value. Example: change Break to Breec: last letter has dropped 8 steps on the table, while second-last has risen 4 steps, leaving the total value unchanged.
The game makers appear to have thrown in some "rogue" codes, which are deliberately designed to have a particular characteristic and do not give the same map as others with the same value.
In Imperialism, for example, Scotland is mostly hills but equivalent "value" codes such as Scotlamf and Scotlalh and Okotland and Scoujand are all the same but quite different from "Scotland". In some cases, at least in Imperialism, the outline of the map is the same but the terrain is different: "Nepal" is frighteningly mountainous whereas its equivalent codes such as Ocpal and Neped have the same coastlines and rivers but are not particularly mountainous. As an extra quirk, though, Nepal gives a fort to a hamlet just north of the green GP; Ocpal has it too, but Neped does not.
More study is desirable!!
Some map keys define "cheats", with the same basic effect except that the distinguishing characteristics are generally known to players.