For almost 15 years I've wondered what is the preferred format for GPS coordinates, such as if you need to report an emergency and need help from a helicopter.

Just this week I was involved in search and rescue operations. I heard in a meeting that helicopter pilots prefer receiving coordinates in the latitude-longitude format of degrees, minutes, and decimal minutes (not decimal degrees or decimal seconds or UTM). They can receive GPS data in other formats, but then it takes time for them to convert it to decimal minutes. Either NAD83 or WGS84 datums are OK, which were said to be close enough to each other.

Of course different locations and organizations likely vary with their preference, but at least I finally heard a preferred format from someone.