On Wednesday, October 24, 2012 12:15:03 PM UTC-6, John Firth wrote:
Forty years ago I put some effort into electrostatic

L/R detection of thermals. The big probelm is the vertical

component of the general gradient which is at least an order of magnitude

bigger than the horizontal part.

This meant that using tip mounted sensors, the vertical distance

between the tips times the vertical gradient would have to be

compensated for; these days with micro computers and roll rate

sensors,this might not be so difficult.

My approach was to mount probes fore and aft and try to fly

a constant pitch angle. (speed)



There were fields I could detect but never resulting in

finding a thermal by turning slowly L and R.

A real sucess was detecting a field across an airmass boundary

( a weak pseudo front, shown by haze) and confirmed by

several passes each direction. There was weak lift

but the haze variation gave this away and I only detected the

field as I flew through it.

The 25m plus spans of some gliders could allow a better

signal.



I await further initiatives with interest.



John Firth, old but no longer bold pilot.



On a few occasions, I have observed soaring birds fly quickly towards a

p=

oint where they found a thermal - sometimes a distance of about a

kilometer=

.. The speed and direction of them indicated to me that they were flying

to=

an objective and not just hunting randomly. If so, this means that they

c=

an detect thermals remotely using their senses. If we can figure out how

t=

hey are doing this, there is a chance we can build instruments to

replicate=

their method.

=20

=20

=20

Having studied the possibility of using electrostatic methods (thermals

a=

dvect space charge from the ground and dust devils are actively charged

by

=

particle collision), this is very short range and not likely the

mechanism

=

birds are using. I would guess it has to be visual.

=20

=20

=20

Mike



I suspect it is visual for birds. The have far better vision than we and

c=

an probably see small objects like seeds rising with the thermal. They

may=

also possess special visual processing centers in their brains evolved

to

=

detect thermals.



I suspect the "one shot" DARPA program works the same way by detecting

embe=

dded objects like dust and seeds moving across the field of view then

using=

powerful algorithms to process the data. Range the objects as they move

a=

cross the field and the direction and speed of the wind can be

determined.



What's interesting to me is the comment that the device will work out to

th=

e maximum effective range of currently fielded sniper rifles. .50

caliber

=

rifle ER's can exceed 3000 meters. There is also a comment elsewhere

indic=

ating the DOD wants to issue this to every soldier so it can't be too

expen=

sive.



In about that same time frame I worked on a set of paper charts showing data collected with an airplane traversing Mojave Desert thermals in mid-afternoon. The sensors included field mills for electrostatic charge and aerosol detectors in addition to the usual - temp, humidity etc.. The only consistent indicator of a 'thermal' was rising air. I think any successful remote thermal detector will have to "see" air motion directly.