The time taken for the Navigator to complete a fix and also the accuracy of that fix can be changed in the OFEV. The time and accuracy of the fix is generally set to reflect the time it would take to get up on deck and take the sighting with a sextant and then do the required mathematical calculations etc. If you want, you can set it so you can get instant GPS accurate positions but I'm sure that by doing so would detract from the realism trying to be achieved.
