Radar Altimeters for Drones

Joined
Jun 10, 2016
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8,000' up in the Rockies
#1
I came across something with my new P4Pv2.0 a couple of days ago. My five DJI Drones are basically my old boy toys and after flying small and large Airplanes and Helicopters Commercially Internationally for over 50 years I'm not going to start flying my toys commercially. I usually spend most of my time just figuring out how to properly fly what I have. A few days ago a friend of mine was going to bail hay from one of his fields that was about 3/4 of a mile long and he asked if I could video him. I usually fly my drones LOS close in or fairly high AGL as I'm up at 8,000' + ASL in the Rocky Mountains and I've got vertical cliffs some as high as 2,500' AGL and also very high 100'+ trees in the surrounding areas. I do try to fly no higher than 400' AGL most of the time. When I caught up to my friend's tractor he was at the far end of his field and I took off from the opposite end. While enroute I descended down from about 50' AGL to about 30' or less AGL visually using my Huawei Mediapad T3 8" Tablet and fairly close in and when I looked at my height (AGL) on my Tablet it worried me as even though the field looked flat it was higher at the far end than at my takeoff point. It was an extremely windy day but my P4Pv2.0 took the wind without a problem except for the constant high wind warnings. I got some fantastic video coverage but I got to thinking of radar altimeters like what I used in years past. I know that on the Round the World non-stop flight of the Rutan Voyager flown by Dick Rutan and Jeana Yeager back in 1986 they jury rigged a very light weight range finder from a Poloroid Camera for their height AGL. I know that my P4Pv2.0 advertises that it will climb following the increasing terrain but
I haven't used that mode yet on this or on my Mavic Pro. My question is what is available to mount on a drone or has anyone figured out how to utilize the bottom sensors of a P4Pv2.0. According to my friend I descended down to less than 10' AGL on some of the close-ups and it would've been great if I could actually have seen my actual height AGL.
 
Joined
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#2
All of the obstruction sensors are ultrasonic and so have limited range. They do try to tell you distances although they aren't terribly accurate. A height above ground sensor would be a wonderful thing to have but I doubt that radars are going to be the answer. For the power / weight / cost budget that these drones entail, I'm thinking even the new solid state radars are going to be a couple of orders of magnitude away from being available for cheap drones.

A laser rangefinder, perhaps but haven't seen anything so far.
 
Joined
Jun 10, 2016
Messages
200
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Location
8,000' up in the Rockies
#3
Thanks for looking WetDog. I'd love for FJI to adapt something such as what they did with their Terrain Follow Mode: In this mode, the aircraft uses its Downward Vision System to maintain height above ground between 1 and 10 meters. I wound up ignoring the negative readout that I was basically underground and kept following the tractor maintaining my height visually utilizing my tablet. Many years ago before the proliferation of Radar Altimeters we'd land both airplanes and helicopters onto unlit fields at night using our landing lights.
 

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