I've been finding and reading maritime SAR documents from all over the internet. In one from NZ this phrase pops up:

"Uncertainty over the location of the target at the datum point will result in a minimum search area of 144nm2."

Where does that number come from? Well that took me another 4-5hrs of reading to work out. It's based on a set of calculations where you draw a 6nm radius circle around the last known location, create a square with tangential sides, and that is 144nm^2.

The moral is: use foot/end notes if you're writing a technical manual, you pricks.