Navigation for dummies

Usually seismic in the North Sea have an ED50 navigation, but sometimes they come in WGS84. The difference is a little over 100 meter. Sometimes you might even come across a dataset that claims to be ED50 which is really WGS84 shifted the wrong way. Shit happens.

I was going to merge an old dataset over Brage, MN9201, with adjacent surveys, and it didnt match.

what I did was to compare time-slices of the surveys in the overlap. Zooming in I could establish that a westward shift of 150 meter and a southward shift of 175 meters gave a good match. I verified it for 6 timeslices between 250 and 3000ms. Cross-correlation in the overlap started to act normally.

Shown is a timeslice from appr 1200ms, scale is 2,5x2,5km