Interesting use of Marine equipment for land use 
Basically a standard for location sharing in an amateur radio world is APRS. In europe search-rescue and law enforcement people use trunked radios like TETRA or TETRAPOL with their own location interface.
There is a really good location tracking and map application that is widely used, and not only by search-rescue teams in europe Locus Map helps with searching for lost peopleLocus, but it is missing an interface like we have for ATAK. It should be possible, but @menion would need to help (discussed in a thread about Offline Maps) - ideally directly from Locus to Meshtastic device without any other app.