How do you fine tune a stargate?

Question

In the Stargate universe DHD and the computer system used by SG command can 'fine tune' the gate address and make sure despite the gates relative positions changing (due to, as Jeff points out Stellar drift), that they can lock on.

Here is an image of the dialing system/co-ordinates

To my knowledge, the far blue points are fixed by the chevrons. If the chevrons are wrong there should be nothing you can do. Also I was under the impression only the the chevrons in on the gate determined the location the gate went to. So how do you fine tune a stargate, when you only have chevrons to adjust, if they can be adjusted?

Answer 1

They don't fine-tune, they compensate for stellar drift. This is a feature of the DHD that was not duplicated by the SGC's dialing computer.

In later seasons, greater familiarity with DHDs and gates in general lead the SGC to be able to incorporate this into their computers in near-real time (unlike the days of chugging the computer had to do in early seasons). This is the only way they could do things they do in the later seasons - where they are handed a random set of coordinates (not from the walls at Abydos) and dial them immediately.