Yes it's while you are stationary.
Few hundreds meters does not matter same like +-1 minute interval inaccuracy, since you are unable to calculate with 0.1 degrees bearings anyway.
To be honest, you can calculate cotangents just with one decimal accuracy at all, its enough
You'll end up with 1-3 degrees target's course inaccuracy, which is ok i think, if you want real precise results, you should use longer period between bearings checks (20-30 minutes) and try to stay in around 100m from first bearing position..
Most of the time you dont need it, you can always confirm result next time around one hour after...
I always confirm it opticaly at firing position, where you need it accurate for your eels, but don't care much while i have it just for approach.
Since hydrophone can reach around 40km you cant lost contact if game dont despawn it..