Global mapper Latitude/Longitude config tutorial for ArmA 3 real world data terrains.

Load global mapper project, drag a box around bottom left user created feature grid vertice.

RMB → vertex editing → set position of selected vertices.

Tick geographic coordinates (latitude/longitude).

Copy paste latitude and goto latlong.net website, paste values to latitude box. Repeat this for longitude.

Note that this websites longitude seconds input box only accepts integers (full numbers, no XX.XXXXX).

Click convert to decimal degrees button and now you have two values. Copy paste lat to mapArea[] first line, shown below

mapArea[] =
{
	14.60974078, 42.84222222, // latitude here
	,  // longitude here
};

Back in global mapper drag a box around top right user created feature grid vertice, get the coordinates same as latitude.

Paste them to mapArea[] second line, shown below

mapArea[] =
{
	14.60974078, 42.84222222, // latitude here
	15.35597344, 43.59888889 // longitude here
};

Next we get the center latitude longitude coordinate for the terrain, go back to global mapper, select the whole user created feature grid, RMB → crop combine/split/split functions → subdivide quadliteral area. Use grid number of rows and columns: 2, click OK. On modify feature info dialog click OK.

Drag a box around the vertice in center of your user created feature grid, get its coordinates same way we did above.

Paste these values normally, except latitude is with NEGATIVE number if its north of equator

latitude = -14.98310431;
longitude = 43.21916667;

Finally grab the mapZone value from global mapper status bar (bottom) where it says like UTM 38N.

mapZone = 38;