I thought others might be interested: On Monday we flew a selection of quads and hexicopters in the path of an X-Band weather radar in order to determine whether the radar could see them and if so, how well.
We flew two 3DRobotics IRIS+ quads and a home-made hex controlled by a 3DRobotics PixHawk. By using them we could easily log all of the vehicle state information and later compare that to what the radar estimated.
We're still crunching the numbers, but we know the radar definitely saw the vehicles with an accuracy of less than 3m in range (maybe better, but we're still working on the analysis) and we believe you can even measure the RPM of each individual motor. We tried distances of 10m out to 400m (up to 100m vertically and out to 400m horizontally). Later in the month we'll go out to 2km. We'll also test our bigger vehicles (google "SnotBot" if you want to see some). I'll post more particulars as we get them. Pic attached.
Also, a big shout-out to the folks at 3DRobotics for helping us with the equipment by giving us an academic discount on all of the hardware*. Given how fast my undergrad students chew through equipment, that helped a lot! (they broke two in testing in just one afternoon).