I may have gotten a little carried away with this, but now its' beginning to bug me. Keep in mind that I'm using SEIV version 1.49, so any of this may have changed in later versions.
Here's what I know:
1. It doesn't matter where you are in the system that you're opening the warp point from. It will always open in the same sector of the destination system.
2. Where the hole opens in the destination is determined only by the relative positions of the two systems, and the distance bewteen them doesn't matter.
3. The function used does not involve trigonometry.
4. There is some oddball behavior in certain positions (imagine that
), but the results are consistent.
I'm going to do some more mapping, and when I think I know how it works I'll be back here with the results.