How ArmA 3 handles lat / lon coordinates.
Positive latitude is above the equator (north), and negative latitude is below the equator (south).
Positive longitude is east of the prime meridian, while negative longitude is west of the prime meridian (a north-south line that runs through a point in england).
Latitude is reversed in ArmA 3, negative latitude is north.
See also Global Mapper Latitude/Longitude Config tutorial.