The most useful and mystifying land-nav hack I ever performed was to locate the precise location of our patrol on a map by shooting a pair of back-azimuths to a pair of known mountain peaks.
“That’s great, kid! Don’t get cocky!”
During the 'evening meeting' while on an operation SW of DaNang, our company CO gave our current map position. Since I was part of the 81mm mortar forward observer team, I'd been constanty following our position all day and knew that we were in a different location.
When I raised my hand and then disagreed with the 'Skipper', several 2nd Lt platoon commanders gave me (a lowly L/Cpl) dirty looks. I asked to have "the guns" fire a Willie Pete round at two separate points. Everyone shot a 'resection' (a pair of back-azimuths) and then agreed with me.
Later, in the middle of the night, the NVA hit us. If I'd taken the Skipper's location, I would have ended up calling down the first fire mission right on top of our heads.
Sometimes it is REALLY IMPORTANT to know your exact location!