If you're surrounded by big trees (as some of us are here in the Pacific Northwest) a RoofTopAdHoc won't cut it. You need to put up a big tower in order to get LineOfSight to your next node. Or, you could put your node up in a tree...maybe.
Here's a couple items that might help with building an antenna-stabilizing mount that would allow you to use a DirectionalAntenna in a tree, even when the wind is blowing.
an electronic compass sensor (But it costs about $700)
a cheap compass board ($50) from the same company (but may be discontinued??)
a compass/accelerometer/ceramic gyro (USB) - can be sampled for free
You could track the distant node's radio signal itself and steer the antenna to stay pointed at it, like radar people do.
You could track a light source, either at a nearby reference object or at the far end of the link. MikeCook mentions some whitepapers
Some other practical issues.....
- climbing the tree (safely)
- getting power to the platform (for node and for actuator motors)
- mounting stuff to the tree
- remote administration of node and platform gear
PersonalTelco has a pretty good related page; NodeUpaTree - an OrinocoRg1000 AP with an 8dBi omni.
