[TowerTalk] New FAA regulations affecting towers

[jimlux]

On 7/18/16 6:23 AM, Richard (Rick) Karlquist wrote:
> Haven't seen this mentioned:
>
> Why don't they require these low flying planes to
> have radar that would "see" power lines and towers?
>


that's actually a pretty challenging radar design problem: especially if 
you want to do it reasonably inexpensively.   Dept of Defense has been 
studying that problem for decades - they too would like to avoid running 
into wires and poles sticking up unexpectedly.

The geometry of the radar vs the ground clutter (and your target) is 
continuously changing.  How do you distinguish a tower, or wire, from 
the soil surface which has essentially the same range and range rate.

Unlike a air defense (surveillance) radar sweeping out 100 mi radius 
once every few seconds looking for something which is moving at a rate 
substantially different than the ground clutter, what you're asking for 
is some sort of microwave imaging system with a fairly fast frame rate 
and very good angular resolution and coverage.  (as in better than human 
vision, because the Mark I eyeball is what's used now, and isn't sufficient)

Right now, we have doppler radars like those used in a Tesla and other 
collision avoidance systems: but those basically provide a single "range 
- range rate" output for a hybrid of strongest and/or closest return.  A 
fairly simple doppler filter will find the "other vehicles" vs the giant 
return from own motion.  They have limited angular resolution (if any..) 
  Some of the mmWave units that are used in farming applications 
(automated tree pruning and the like) have phased array antennas which 
can scan vertically and horizontally, but they don't have fast frame rates.

LIDAR and laser scanning are both popular in autonomous vehicle work, 
but have a tough time detecting things like wires, and, of course, don't 
work well in weather that is not optically clear (the early morning haze 
and ground fog problem).


Overall, a data base of reasonably accurate positions would seem to be 
the best solution.  Not in a "use the position to fly around it" but in 
a "did something new pop up last night that I am unaware of it".