I have been using XCSoar thermalling assistant in 8 club gliders.
As pointed out earlier, it works better when connected with a
variometer. But it gives you some idea what is happening even
with GPS only. My experience is, that the most important thing
is to adjust timing of you corrections for each glider. It's easier
now, when we have 3 or our gliders with same variometer/flarm
systems.

I was flying few days ago using the latest XCSoar test version.
There was an interesting new feature - while circling, it is
drawing an arc in front of the glider, predicting where your
current bank and speed will bring you. It worked surprisingly well
when I was using it on backseat of our Janus, with LG phone and
without flight computer connection. The glider track was set to
color the lifting areas yellowish, sinks blue(s), and I was using
this new graphic tool to aim my course to the area of strongest
lift.

I also had the thermal assistant as an infobox, as well as the
thermal gain graph.

Since these systems tell you what has happened past 30 secs
and where, they might give you some information you can use to
make your corrections. Or to leave the thermal. Nothing more.

XCSoar seems to have a feature that calculates the central
point of the lift, but I have not found that useful. Maybe I have
not got the right idea off how to utilize it.


At 13:57 10 August 2013, wrote:
On Tuesday, July 30, 2013 1:54:13 AM UTC+1, jfitch wrote:
Thermals may not be circular, but your glider flies in a pretty
good
appr=
oximation of a circle. So the cylindrical graph depicted in
Winpilot is
all=
the information you can really use. XCSoar's polar graph might
fool you
in=
to thinking that is the shape of the lift - but it is a polar graph
of
stre=
ngth around a fixed radius circle, not a map of the thermal. Oh
yeah they
a=
re different!

'fixed radius circle' implies to me that XCSoar's assistant is
trying to
es=
timate the lift over a fixed area - eg a 250m wide circle. Just to
clarify:=
XCSoar's thermal assistant is simply a 36-point plot of the lift
recorded
=
vs heading over the last turn. While your heading lies within a
single 10
d=
egree block, one of these points is continuously updated with
your
instanta=
neous vario value. When your heading crosses into the next 10
degree
block,=
the next point is updated, and so on.

In practical terms this means that any sections where you hold
a constant
h=
eading are ignored on the plot. As an extreme example, imagine
you're
flyin=
g a racetrack pattern between two cores. You've turned the
first 180
degree=
s in the first core and have just completed the remaining 180
degrees in
th=
e second core. The top half of the thermal assistant would
show the lift
en=
countered during your 180-degree turn in the first core, and
the bottom
hal=
f would show the result of your 180-degree turn in the second
core. Any
lif=
t or sink you encountered on the straight leg between the first
and second
=
cores would not be represented on the plot.

The line in the middle of the plot just points to the centre of
the
polygon=
..