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#61
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When are thermals not circular and do thermal helpers assume that they are?
Thanks - now I see what you mean. My confusion was because XCSoar does a
pretty good job of predicting the wind drift (due to getting good information from my CAI302) and so the flight track (rather than ground track) is displayed while circling. This makes it pretty easy to get back to the lift if, due to inattention or poor decisions, you get out of it. Slightly off topic, but IIRC I can set up the software so that it accounts for wind drift while circling and not in straight flight. I say this because I use the track to stay in the best lift while wave flying. "jfitch" wrote in message ... On Sunday, August 11, 2013 10:19:40 AM UTC-7, Dan Marotta wrote: What are you trying to say. Seems to me that the airmass is carrying the thermal along and the glider with it. With that premise, circling in calm air or in a wind makes no difference. I've thermalled straight up and with a 20+ kt drift down wind. I never had to hold heading into a wind to maintain center in a thermal. Or do I misunderstand what you're saying? If that's the case, please elaborate. ... On Saturday, August 10, 2013 8:43:05 AM UTC-7, Dan Marotta wrote: Your glider is drifting with the wind, too... Unfortunately, the earth, and the GPS system that tracks with it, is not..... It makes a difference if you are trying to relate your thermaling track to a track projected to the ground. Some thermal assistants (like SYM) draw a track on the ground color coded by climb rate. If you are drifting with the wind, this track quickly drifts upwind relative to you and the airmass (which are drifting downwind). Therefore the next time around your circle, the track will not have much relevance. The only thing that matters (as you have said) is the glider relative to the airmass, which the GPS cannot accurately track and plot. That relationship has to be inertially derived, or simple inferred to be static. The GPS plot is relative to the earth, which can be thought of as moving underneath you at the speed of the wind. Such a plot is of little value when thermaling though they can be useful for ridge and wave, which are effectively anchored to the earth. There have been some attempts to guess the drift of the thermal from an assumed or calculated wind speed, but most thermals where I fly are not so well behaved. |
#62
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When are thermals not circular and do thermal helpers assume thatthey are?
On Monday, August 12, 2013 8:49:40 AM UTC-7, Dan Marotta wrote:
Thanks - now I see what you mean. My confusion was because XCSoar does a pretty good job of predicting the wind drift (due to getting good information from my CAI302) and so the flight track (rather than ground track) is displayed while circling. This makes it pretty easy to get back to the lift if, due to inattention or poor decisions, you get out of it. Slightly off topic, but IIRC I can set up the software so that it accounts for wind drift while circling and not in straight flight. I say this because I use the track to stay in the best lift while wave flying. ... On Sunday, August 11, 2013 10:19:40 AM UTC-7, Dan Marotta wrote: What are you trying to say. Seems to me that the airmass is carrying the thermal along and the glider with it. With that premise, circling in calm air or in a wind makes no difference. I've thermalled straight up and with a 20+ kt drift down wind. I never had to hold heading into a wind to maintain center in a thermal. Or do I misunderstand what you're saying? If that's the case, please elaborate. ... On Saturday, August 10, 2013 8:43:05 AM UTC-7, Dan Marotta wrote: Your glider is drifting with the wind, too... Unfortunately, the earth, and the GPS system that tracks with it, is not..... It makes a difference if you are trying to relate your thermaling track to a track projected to the ground. Some thermal assistants (like SYM) draw a track on the ground color coded by climb rate. If you are drifting with the wind, this track quickly drifts upwind relative to you and the airmass (which are drifting downwind). Therefore the next time around your circle, the track will not have much relevance. The only thing that matters (as you have said) is the glider relative to the airmass, which the GPS cannot accurately track and plot. That relationship has to be inertially derived, or simple inferred to be static. The GPS plot is relative to the earth, which can be thought of as moving underneath you at the speed of the wind.. Such a plot is of little value when thermaling though they can be useful for ridge and wave, which are effectively anchored to the earth. There have been some attempts to guess the drift of the thermal from an assumed or calculated wind speed, but most thermals where I fly are not so well behaved. XCSoar does have the option to drift your track at the assumed wind speed to account for this problem. I have found it not to be accurate enough to make it usable (may depend on where you fly). The XCSoar thermal assistant does about the same thing as Winpilot, but the presentation is not as good: the correction arrow is inusfficiently scaled, the polar graph very blocky (if it is really plotting every 10 deg), no other information presented such as average or graphed climb, flarm targets, etc. |
#63
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When are thermals not circular and do thermal helpers assume thatthey are?
I bit the bullet and purchased an Oudie 2. New system worked great and was very visible in somewhat darkened skies due to overcast. Thermal assistant seemed to be much improved with version 4.50.003. So long WinPilot/PDA. Thanks to Craggy Aero for their prompt service.
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#64
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When are thermals not circular and do thermal helpers assume thatthey are?
On Thursday, August 1, 2013 3:20:49 PM UTC-7, Naviter Info wrote:
I dare to say that accurate thermal assistants are a myth and that head down time during circling is a waste unless you are consciously learning a particular technique. At the same time - I do keep the "ding ding" thermal assistant active most of the time. Mainly because at times I become useless when I am talking on the radio, looking at my landing options or become plain old tired. That's when the thermal assistant's "ding ding" is usually right and very useful. Regards, Andrej Kolar Thanks for the reworked thermal assistant Andrej. I do like the zoom/tracking feature as it allows me to explore a spread out area of lift and still return to the hotspot(s) with some reliability. It also allows me to account for wind drift a bit better. I do think the arrow and beep in the climb optimization is still a bit irregular as it is sometimes seems 180-degrees out of sync from where the stronger lift turns out to be. I'm not sure how you are integrating the climb rates around 360 degrees, but it feels as though the arrow points to the strongest single 20- or 30-degree sector of lift rather than the direction to move the circle to maximize the rate of climb around the entire circle. I realize that with a choppy thermal it is easy to confuse any estimation algorithm, but there is something my brain does (and WinPilot seems to do) that still nets this out a bit better. I wonder if there are more parameters you could expose to allow some tuning to individual preferences. Lastly, an average climb line graph over the past 5-7 circles would also be welcome - I make due today with the 20 second averager versus the climb for the thermal, but a trend line would be more intuitive. Again, nice improvements - I agree it is very useful in those cases where I have gone brain dead for a moment, but I also use it to speed coring thermals any time when I am unable to core on the first turn and a half - which is most of the time. 9B |
#65
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When are thermals not circular and do thermal helpers assumethat they are?
jfitch wrote, On 8/11/2013 9:59 PM:
It makes a difference if you are trying to relate your thermaling track to a track projected to the ground. Some thermal assistants (like SYM) draw a track on the ground color coded by climb rate. If you are drifting with the wind, this track quickly drifts upwind relative to you and the airmass (which are drifting downwind). The Thermal Assistant in my version of SYM does not draw a track on the ground (of course, the map shows the ground track); instead, it opens it's own window with no map info on it, and uses about 20 or so small circles ("bubbles") arranged uniformly in a large circle to display the thermal. Each bubble is sized and colored to depict the lift at that point: bigger bubble, bigger lift; red is stronger, blue is weaker (the actual colors can be selected) In essence, your circles do overlay each other, no matter how much the glider drifts with the wind. I never had trouble with wind drift when using the Assistant. ClearNav, what I am now using, does use a ground track, and it's hard for me to make sense of the the thermal is doing from it's depiction. I'm nagging them about this, and I hope it will be improved soon. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl |
#66
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When are thermals not circular and do thermal helpers assume thatthey are?
On Tuesday, August 20, 2013 1:55:53 PM UTC-7, Eric Greenwell wrote:
jfitch wrote, On 8/11/2013 9:59 PM: It makes a difference if you are trying to relate your thermaling track to a track projected to the ground. Some thermal assistants (like SYM) draw a track on the ground color coded by climb rate. If you are drifting with the wind, this track quickly drifts upwind relative to you and the airmass (which are drifting downwind). The Thermal Assistant in my version of SYM does not draw a track on the ground (of course, the map shows the ground track); instead, it opens it's own window with no map info on it, and uses about 20 or so small circles ("bubbles") arranged uniformly in a large circle to display the thermal. Each bubble is sized and colored to depict the lift at that point: bigger bubble, bigger lift; red is stronger, blue is weaker (the actual colors can be selected) In essence, your circles do overlay each other, no matter how much the glider drifts with the wind. I never had trouble with wind drift when using the Assistant. ClearNav, what I am now using, does use a ground track, and it's hard for me to make sense of the the thermal is doing from it's depiction. I'm nagging them about this, and I hope it will be improved soon. -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl The latest version of SYM draws a color coded ground track, as well as the bubbles. Still has quite a ways to go to catch up with what Winpilot had in 2005.... |
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