"Lars P. Hansen" wrote:

OK, here we go: Could devices like this not also be used to detect thermals?
The description in the link below about how the laser "sees" minute dust
particles in the air seems to be well suited to thermals.


I don't buy the explanation they give in the cited url (http://www.navysbir.brtrc.com/succes...navsea_p3.html)
They pretend the device measures the speed and direction of dust particles
from the shift in the frequency of reflected light, this is well known
as Doppler effect and can only give the radial component (toward or away
from the sensor) of the speed, not its value and direction. For thermals
we are interested in the speed component which is nearly perpendicular
to the measured component, so this would be of little interest. Of course
whith several such devices on the ground, all the 3 compenents of airmass
speed could be measured, maybe this in the intended use of the device as it
is advertised, but in a glider you don't have sufficient vertical distance
for putting 2 devices which could provide an accurate value for the vertical
component of the speed.