@David Smith good question and honestly a really common one when people first see that 50km number.
So to be straight with you — that 50km figure is the drone-to-drone spec, meaning both modules are airborne with no ground reflections and essentially clean sky between them. The ground-to-ground number is 5km, and the man-to-drone (one end elevated, one on the ground) sits at 15-20km. Those three numbers tell you most of what you need to know about how heavily the spec depends on elevation and clearance.
For your semi-rural scenario with low buildings and some trees, you're going to be somewhere in the middle. BLE at 2.4GHz doesn't punch through terrain the way lower-frequency RF does — foliage and buildings will eat into your link budget, though scattered low obstructions are nowhere near as punishing as dense urban canyon environments. If you can get even modest elevation on one or both ends (rooftop mount, small mast, elevated structure), you'll recover a lot of that margin. The receiver sensitivity and external amp design on the MultiNav is doing real work here, so you're not starting from a bad place like you would with a commodity module.
Realistically for your described environment, I'd plan around the 5km ground-level figure as your conservative floor and expect meaningfully better with any elevation advantage. If you want to share more specifics about the deployment geometry — like whether you can get one node up high — I can probably help you think through what's achievable.
