When are thermals not circular and do thermal helpers assume thatthey are?

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 approximation 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 into thinking that is the shape of the lift - but it is a polar graph of strength around a fixed radius circle, not a map of the thermal. Oh yeah they are different!

'fixed radius circle' implies to me that XCSoar's assistant is trying to estimate 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 degree block, one of these points is continuously updated with your instantaneous 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 heading are ignored on the plot. As an extreme example, imagine you're flying a racetrack pattern between two cores. You've turned the first 180 degrees in the first core and have just completed the remaining 180 degrees in the second core. The top half of the thermal assistant would show the lift encountered during your 180-degree turn in the first core, and the bottom half would show the result of your 180-degree turn in the second core. Any lift 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..

On Saturday, August 10, 2013 6:57:04 AM UTC-7, 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 approximation 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 into thinking that is the shape of the lift - but it is a polar graph of strength around a fixed radius circle, not a map of the thermal. Oh yeah they are different!



'fixed radius circle' implies to me that XCSoar's assistant is trying to estimate 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 degree block, one of these points is continuously updated with your instantaneous 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 heading are ignored on the plot. As an extreme example, imagine you're flying a racetrack pattern between two cores. You've turned the first 180 degrees in the first core and have just completed the remaining 180 degrees in the second core. The top half of the thermal assistant would show the lift encountered during your 180-degree turn in the first core, and the bottom half would show the result of your 180-degree turn in the second core. Any lift 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.

Thanks for clarifying my explanation, that is precisely how I thought it (and Winpilot) works. A graph of lift as a function of angular (heading) displacement.

I do not understand the value of plotting lift strength vs. geographical position as is done by some programs. In the thermals I fly, the thermal is at least drifting with the local wind, and often not in an orderly way. The last circle's track has little predictive value for the next (they may be displaced by half a diameter or more) unless the last circle's track is drifted with the predicted wind - and that is not reliable near a rough western thermal. This does have some value in ridge or wave flying, but not in thermals.

Your glider is drifting with the wind, too...


"jfitch" wrote in message
...
On Saturday, August 10, 2013 6:57:04 AM UTC-7, 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
approximation 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 into thinking that is the shape of the lift - but it is a polar
graph of strength around a fixed radius circle, not a map of the
thermal. Oh yeah they are different!



'fixed radius circle' implies to me that XCSoar's assistant is trying to
estimate 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 degree block, one of these points is continuously updated with
your instantaneous 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
heading are ignored on the plot. As an extreme example, imagine you're
flying a racetrack pattern between two cores. You've turned the first 180
degrees in the first core and have just completed the remaining 180
degrees in the second core. The top half of the thermal assistant would
show the lift encountered during your 180-degree turn in the first core,
and the bottom half would show the result of your 180-degree turn in the
second core. Any lift 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.

Thanks for clarifying my explanation, that is precisely how I thought it
(and Winpilot) works. A graph of lift as a function of angular (heading)
displacement.

I do not understand the value of plotting lift strength vs. geographical
position as is done by some programs. In the thermals I fly, the thermal is
at least drifting with the local wind, and often not in an orderly way. The
last circle's track has little predictive value for the next (they may be
displaced by half a diameter or more) unless the last circle's track is
drifted with the predicted wind - and that is not reliable near a rough
western thermal. This does have some value in ridge or wave flying, but not
in thermals.

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=
..

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=
..

On Monday, July 29, 2013 9:00:11 AM UTC-7, son_of_flubber wrote:
I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.

I find that the SeeYou Thermal assistant works very well. Why don't you think it works. The manual on page 30-31 of the Oudie manual explains how it works

Richard
www.craggyaero.com

On Monday, July 29, 2013 7:44:44 PM UTC-6, Richard wrote:
On Monday, July 29, 2013 9:00:11 AM UTC-7, son_of_flubber wrote:

I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.



I find that the SeeYou Thermal assistant works very well. Why don't you think it works. The manual on page 30-31 of the Oudie manual explains how it works



Richard

www.craggyaero.com

Jon, I was flying in Northern UT, Idaho and Wyoming but it sounds like the same air mass. I did get a god OLC score on 7/26 but it had nothing to do with my thermalling ability.

Richard,

SYM just doesn't seem to work well. I have read the manuals and tried many different settings. Here are a few observations:

1. The interface is not as intuitive and easy to understand as WP. I have tried both type of displays and neither is great. I use the circle system most of the time now. I wish the circle diameter was constant rather than relative to each other. WP graphic is so much better on a 1 to 10 scale the WP is a 9 and the SYM is about a 4.

2. The timing appear to be off by about 30 or more degrees with SYM. Very often if you open up in the direction of what should be stronger it is not correct.

3. The timing of it turning on and off is random at best and frustrating at worst. It usually takes two or three full turns to come on and sometimes longer. Those first few turns are when you need it the most. WP would come on about 90 to 120 degrees into a turn. SYM tends to come on when you are finally cored and don't need it as much. It also comes and goes randomly when still in a thermal.

4. You can not toggle it on and off easily. With WP I had a button to push to turn it off if I was thermalling and wanted to see other information. With SYM I added the button to the menu bar but is does not work well. It will turn off the Thermal circles graphic but leave you in the thermal window.

5. SYM lacks the thermal strength versus time graph. This is extremely useful to determine how you are doing over time and the shape of the curve helps to determine if you need to adjust the circle.

6. In weak conditions where you are looking for very small amounts of lift SYM is correct on the direction about 50% of the time, WP was more like 90%..

SYM has many strengths but the TM is not one of them. I wish they would listen to users and improve it to something close to what WP has. Just offer a WP like TM page for those that want it. On the flipside I wish WP would listen to users and fix the known issues rather than chasing iPhone apps that can not be seen in a cockpit. Too bad neither seem to care about making the best possible product. No real hard things to fix for either company..

TT

On Monday, July 29, 2013 7:44:44 PM UTC-6, Richard wrote:
On Monday, July 29, 2013 9:00:11 AM UTC-7, son_of_flubber wrote:

I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.



I find that the SeeYou Thermal assistant works very well. Why don't you think it works. The manual on page 30-31 of the Oudie manual explains how it works



Richard

www.craggyaero.com

Jon, I was flying in Northern UT, Idaho and Wyoming but it sounds like the same air mass. I did get a good OLC score on 7/26 but it had nothing to do with my thermalling ability.

Richard,

SYM just doesn't seem to work well. I have read the manuals and tried many different settings. Here are a few observations:

1. The interface is not as intuitive and easy to understand as WP. I have tried both type of displays in STM and neither is great. I use the circle system most of the time now. I wish the circle diameter was constant rather than relative to each other. WP graphic is so much better on a 1 to 10 scale the WP is a 9 and the SYM is about a 4.

2. The timing appear to be off by about 30 or more degrees with SYM. Very often if you open up in the direction of what should be stronger it is not correct.

3. The timing of it turning on and off is random at best and frustrating at worst. It usually takes two or three full turns to come on and sometimes longer. Those first few turns are when you need it the most. WP would come on about 90 to 120 degrees into a turn. SYM tends to come on when you are finally cored and don't need it as much. It also comes and goes randomly when still in a thermal.

4. You can not toggle it on and off easily. With WP I had a button to push to turn it off if I was thermalling and wanted to see other information. With SYM I added the button to the menu bar but is does not work well. It will turn off the Thermal circles graphic but leave you in the thermal window.

5. SYM lacks the thermal strength versus time graph. This is extremely useful to determine how you are doing over time and the shape of the curve helps to determine if you need to adjust the circle.

6. In weak conditions where you are looking for very small amounts of lift SYM is correct on the direction about 50% of the time, WP was more like 90%..

SYM has many strengths but the Thermal Assistant is not one of them. I wish they would listen to users and improve it to something close to what WP has. Just offer a WP like TM page for those that want it. On the flipside I wish WP would listen to users and fix the known issues rather than chasing iPhone apps that can not be seen in a cockpit. Too bad neither seem to care about making the best possible product. No real hard things to fix for either company.

TT

On Monday, July 29, 2013 7:48:05 PM UTC-7, Tim Taylor wrote:
On Monday, July 29, 2013 7:44:44 PM UTC-6, Richard wrote:

On Monday, July 29, 2013 9:00:11 AM UTC-7, son_of_flubber wrote:



I'm starting to think that the textbook circular thermal is primarily a flatland phenomena.







I find that the SeeYou Thermal assistant works very well. Why don't you think it works. The manual on page 30-31 of the Oudie manual explains how it works







Richard



www.craggyaero.com



Jon, I was flying in Northern UT, Idaho and Wyoming but it sounds like the same air mass. I did get a good OLC score on 7/26 but it had nothing to do with my thermalling ability.



Richard,



SYM just doesn't seem to work well. I have read the manuals and tried many different settings. Here are a few observations:



1. The interface is not as intuitive and easy to understand as WP. I have tried both type of displays in STM and neither is great. I use the circle system most of the time now. I wish the circle diameter was constant rather than relative to each other. WP graphic is so much better on a 1 to 10 scale the WP is a 9 and the SYM is about a 4.



2. The timing appear to be off by about 30 or more degrees with SYM. Very often if you open up in the direction of what should be stronger it is not correct.



3. The timing of it turning on and off is random at best and frustrating at worst. It usually takes two or three full turns to come on and sometimes longer. Those first few turns are when you need it the most. WP would come on about 90 to 120 degrees into a turn. SYM tends to come on when you are finally cored and don't need it as much. It also comes and goes randomly when still in a thermal.



4. You can not toggle it on and off easily. With WP I had a button to push to turn it off if I was thermalling and wanted to see other information. With SYM I added the button to the menu bar but is does not work well. It will turn off the Thermal circles graphic but leave you in the thermal window.



5. SYM lacks the thermal strength versus time graph. This is extremely useful to determine how you are doing over time and the shape of the curve helps to determine if you need to adjust the circle.



6. In weak conditions where you are looking for very small amounts of lift SYM is correct on the direction about 50% of the time, WP was more like 90%.



SYM has many strengths but the Thermal Assistant is not one of them. I wish they would listen to users and improve it to something close to what WP has. Just offer a WP like TM page for those that want it. On the flipside I wish WP would listen to users and fix the known issues rather than chasing iPhone apps that can not be seen in a cockpit. Too bad neither seem to care about making the best possible product. No real hard things to fix for either company.



TT

Pretty much what he said. I would add that the depiction of all Flarm contacts, with associated information on the Thermal Assistant page is at the very least entertaining and very good for situational awareness.

On Tuesday, July 30, 2013 7:42:18 AM UTC+2, jfitch wrote:

Pretty much what he said. I would add that the depiction of all Flarm contacts, with associated information on the Thermal Assistant page is at the very least entertaining and very good for situational awareness.

The trouble with all these graphic displays is that they require a certain amount of time to look at and analyze the data presented prior to using it to center the thermal. We use audio varios to get away from looking at a needle, and now we have pretty pictures!

I use SYM but not the climb page - instead I have a Themi that consistently reminds me to move towards the stronger part of the circle (wind corrected). Usually I've already decided to move my circle when the Themi lights up, but sometimes it does a better job of remembering where the surge is.

SYM has a provision for an aural cue to suggest when to roll out to move the circle, but haven't tried it.

Considering the age of Themi, and the fact that it uses (as far as I know) only GPS to track the thermal, I'm surprised there hasn't been a second generation Themi2 that would use better sensors to map the thermal, but still keep the simple visual cues (LEDs on the glareshield).

Kirk
66