Finding a block relative to another block.

I'm a little stumped at where to begin. This will be part of a larger script but I'm trying to gain the basic understanding of how it's done.

When constructing a ship via projection, it's projected as a part of an existing grid. The orientation of this existing grid is subjective. When the ship is cut away from the host, it becomes a new entity and that grid is also subject to change orientation.

So my thought is to use a centralized block like a flight seat as a demarcation point....

Finding a block relative to another block.