In the pre Omega days on the Nimrod Mk1 there was a pragmatic approach to high latitude navigation. In in event that we were called out to go a very long way north, it was considered it would be prudent to drop a couple of 8 hour life sonobuoys in the last stretch of open water when confident of our position. We would then proceed to do what was required and on going off task put the buoys on the d/f and homer, update on top and go home.
Job’s a good’n!
YS