I do a 1:1 multi layer blueprint, locate all the bases on one layer, block out land elevations in several others. This is a 10x10 so the file is a 2048x2048 8pixel=1mile. I know what I'm going to sculpt by the time I create the 1:1, so all I need is to map the basic block elevations in different colors. Draw in any major canyons or primary runs of a drainage system. Especially if you are running water from elevations onto a plain with a lake that drains to the ocean with a river. My fun in all this is creating a world and it's topo features. The game takes place in a focus of about a 6mile diameter around fields. The rest is a grand illusion to entertain the eyes of the pilots as they fly to a fight. And then there is the micro structure world for GV combat that can be a real bite in the whatsus...but, I try to keep those guys entertained like on Oceania.
Here is my 1:1 blueprint with the base elevation blocks, primary water, and feilds for one country. I simply make two copies of the field layer, and rotate them to index the center line of each country border. Then I merge them and I have my feilds mapped and can transfer those dots as place holders to the CBM and then onto the terrain. At that point I can sculpt to enhance the location markers and not place an airfield at the bottom of a tiny canyon 1000ft deep. I still need to map out the primary canyons so they are cut during the import, I want straight sides with this one. The majority of airfields are 19miles which kept the action going on Oceania. This time the center pit is for task groups to fight and if you want GVers to not hide, don't place vBases everywhere. Give them spawns to follow the combat and they will happily help out. On this terrain, it will be 50\50 town and map room on the field. This thing will last maybe three days and not bore people for seven.
Note to self: finish the full field layout layer so you can make sure feeder streams run close enough to some percentage of feilds to use bridges.
The strats and three un-capturable airfields are not as important in this case, it's obvious to make a cluster with the three airfields arranged to protect the cluster and HQ. Since Hitech enabled the 163 on Oceania at all three of my un-capturable, I will on this one and again not add Flak feilds.