Which Way is That Thermal?

ContestID67 wrote:
I was sent a link to a gadget some college engineers-in-the-making
built. http://engenius.sece.rmit.edu.au/Abstracts/Page601.htm. It
tries to detect which way a thermal is based on temperature differences
between wing tips. Bright boys.

I have two questions;

1) Have there been other gadgets created to do the same thing? How
well did they work?

Dear Sir:

Look at the Themi:
http://www.themi.de/Themi%20Centering%20Device.htm

And, I've been told that the Zander flight computer --
http://www.zander-variometer.de/ -- has similar capability, but don't
see evidence of this on their web site.

After hearing about the Themi, I *had* to buy one to see how it works.
Having said that, I have been using one for 2 years, and have some
experience with it -- it's a fun toy -- but I"ve been unable to find
any description of how it operates. Some things are obvious: It has a
GPS engine, and probably has a barometric sensor and/or accelerometers.

In any case, the maximum it coiuld do is to use 3-D GPS data to
calculate climb/descent; it could have accelerometers as well; and
sense pressure changes. It could calculate, therefore, the movement of
the glider, make some assumptions about flight, calculate wind, and on
this basis estimate where the best lift *was* so you can go back to it.

In my experience, if I fly in non-erratic circles, it does a pretty
good job of re-finding the last spots of lift after I've wandered away
fruitlessly looking for something better, and in doing this it seems to
compensate for wind.

Obviously, it can't predict the future, so I use my own judgment on
where lift is *going* to be.

It is useful? After 2 years with it, I do feel that I'm better than it
is. I look at the ground and the cloud (if any) and think about the
wind (my SN-10 is invaluable in this regard --
http://www.ilec-gmbh.com/sn10.htm ) and am reliably able to find lift.

But -- in weak or windy conditions, or when, as sometimes happens, I
lose my mental image of the thermal and where I've been, I will
somtimes turn my brain off for a couple of minutes and just "fly the
lights," and more often than not get back into lift.

I do wish that someone who knows the theory behind this gadget would
speak about this, as it would help me understand how best to fly with
it.