Digressing slightly to talk of sonobuoys,
Avtur said
I assume the accuracy of sonobuoy dropping these days allows for higher alts (assuming the sea below can be confirmed clear) so dropping low may not be required anymore
It is not the dropping accuracy that needs to be considered but the determination of where the buoy actually landed.
In the case of a low level release of a tight spacing of buoys the effect of wind drift can be overcome in the same way as stick bombing. From say 20,000 feet, assuming a reasonable windspeed a sonobuoy may land 2,000 yards or move from the release position, it also did not follow that each sonobuoy would be in exactly the same relationship is when it was dropped.
If a sonobuoy then drew a target things became relative.
The crux therefore was finding each sonobuoy in order to get an accurate ground plot and fill in any gaps. It was impractical to on top every buoy but GPS upload could solve that problem - I don't know it buoys can upload their positions.