I wonder if a more feasible approach to thermal detection is using IR
cameras pointed at the ground. From what i can gather, air is a poor medium
for producing IR radiation, whereas presumably any solid object (anything on
the ground) would be much, much easier to detect. A real life example is the
police helicopters following suspects at night with ease, they light up like
a Christmas tree.
I can see that perhaps it's somewhat plausible (in theory) to be perhaps a
few KM from a thermal source, see the signature heat pattern on the ground
and head toward it. The idea being you will be in the general area by the
time the newly triggered thermal reaches your altitude. Of course there are
issues such as wind drift, however in theory i can see how it could improve
general decision making when there is not many other visual cue's to use...
such as cu's.
Having said that, i have no idea as to the technical requirements of such a
camera, weather it would need to be super cooled etc.
Luke
On 27 August 2010 19:34, Martin Gregorie <[email protected]> wrote:
> On Fri, 2010-08-27 at 14:32 +1000, Luke O'Donnell wrote:
>
> Many thanks for posting those links.
> >
> > Have a look at
> > http://www.paraglidingforum.com/viewtopic.php?p=8030#8030
> >
> The girl on the hill with a sensitive thermometer is *not* a spoof.
>
> Competitive free flight model fliers have used ground rigs to find
> thermals for decades. I built my first such system around 1971 and have
> used them when flying small power models ever since - 1/2A and F1J for
> those who understand FF. If you want to know more about these devices,
> look here:
>
> http://www.gregorie.org/freeflight/thermal_detector/thermal_detector.html
>
>
> These days you can buy suitable thermometers over the counter. Digital
> thermometers with external sensors work just fine provided the sensor is
> small and has no thermal inertia work well. The temperature change as a
> thermal goes through can vary from 0.2C on a cool, overcast early
> morning to 2.0C just after midday on a calm, hot, thermally summer day.
>
> If you know what you're looking for you can feel thermals using only
> bare skin. As a thermal approaches the wind speed drops and the air
> feels warmer. A sudden temperature drop and increase in wind speed shows
> the core has just passed. This is the moment you launch the model to put
> it in the thermal. Almost all the wind speed and direction changes you
> notice on the glider field are thermal related: next time you're out on
> a strong day and waiting to fly try it for yourself. The combination of
> wind speed and temperature changes aren't hard to feel. There's usually
> a strong periodicity to them: if you have a stopwatch, use it to time
> the gap between thermals. The gap varies from day to day but is fairly
> constant on any particular day unless conditions change.
>
> I also flew F1A towline gliders but never with a thermal detector.
> Simply towing the model, watching it and feeling what its doing through
> the towline works much better.
>
> > As for LIDAR, see this for actual LIDAR videos:
> >
> > http://lidar.ssec.wisc.edu/movies/index.htm
> >
> Fascinating. Thats' the first time I've seen what Lidar images of
> thermals look like.
>
>
> Martin
>
>
>
>
>
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