We always start with the ground, first textures, then markings, etc.
Most scenery projects ends up badly, because they start with the most exciting stuff, like terminals or control towers, then you switch to the "boring" stuff ( ground markings ), realize you made a mistake ( those *must* be utterly precise ), realize you'll likely have to fix all your already made 3d, get frustrated, and abandon the project. Seen so many times for freeware stuff which started with publishing a screenshot of a terminal or a control tower and a "coming soon" comment.
That's why we always start with the boring stuff first ( ground layout ) and then we start the 3d, based on the more precise markings after all satellite images has been cleaned, perspective corrected, fixed, rectified, etc, etc,