Hi Dan, if you look into the
GWX - 16km Atmosphere option folder you will see that it only contains the Env files & the Scene.dat file. The
same sensors.dat & AI_Sensors.dat are used regardless,( answered my question above) so only the "Atmosphere" has changed", I use the 8k Atmosphere & have both dats set down to around 9k.

Here is a test, run the Navigation Academy mission & using the GWX 8k Atmosphere check the maximum distance in Map with ruler from U-boat, till the Destroyer shows, it is about 12k, now use binoculars, it is around 8k before you can actually see it! Do the same test with 16k atmosphere enabled, both crew (Map) & binoculars will be around 12k!

What you see through binoculars is the difference of the selected Atmosphere, the Map distance to target is determined by settings in the Sensors.dat file, just for fun I changed the Visual range in Sensors.dat to 50k & you should have seen the fps drop at the start of a mission!!