PowerFlarm and ADS-B solution, can we find one?

In the spirit of technical discussion I must point out what seems to me
to be a basic flaw in logic.

The statement that you can gain or lose altitude at 10 m/s (~20 kt) is
certainly valid in the US southwest. However the supposition that two
gliders traveling in opposite directions with 200 meter vertical
separation would be at risk of collision due to one suddenly dropping
and the other suddenly climbing /_in the same airmass_/ does not appear
to be a serious risk. To do this would require one or both of the
gliders to pull up in sink or push over in lift. In reality both would
either pull up or push over thus keeping the vertical separation nearly
the same.

As to the stealth argument, if only ID and (claimed) climb rate are
masked, with position and relative altitude still displayed, where's the
loss in situational awareness? Remember that there are still right of
way rules to follow to avoid swapping paint.

Someone mentioned the danger of one glider pushing over to leave a
thermal as another is pulling up into the same thermal. This is a valid
concern, though a special case. Assuming both aircraft are equipped
with some sort of anti-collision device then a maintained situational
awareness should preclude any abrupt maneuvers in close proximity to
another glider. I realize that some folks have a "get out of my way"
philosophy and no device can be expected to keep them from doing
something unexpected.

On 1/5/2016 3:56 PM, Andrzej Kobus wrote:
On Tuesday, January 5, 2016 at 9:02:51 AM UTC-5, wrote:
On Monday, January 4, 2016 at 6:08:40 PM UTC-5, Andrzej Kobus wrote:
I think it is time to end this back and forth ping pong about restricting the use of PF. We have to agree to disagree and try to come up with a solution that could work for both groups.
Let's try to define some criteria that might be acceptable to all:
1) Should targets be visible on PowerFlarm display?
2) If (1) is "Yes" then what is the desired distance at which targets should be visible on PowerFlarm display?
3) Do we allow for displaying altitude of another glider on PowerFlarm display?
4) Do we allow for displaying information pertaining to climb rate or simply indicate if a glider is ascending or descending?
5) Do we need to be able to identify a conflicting glider?
6) What are the minimum requirements for identification of conflicting traffic?
7) Should we aim not to degrade PF functions for non-contest participating PF users in the area of a contest?
8) How do we deal with ADS-B in a glider? I have ADS-B out plus I have ADS-B in on both 1090 and 978.
9) Anything else?


In the interest of having a constructive discussion on the topic- THANK YOU ANDRZEJ!, I will provide my personal opinions.
1- Yes
2- I have suggested 5km previously
3- Relative altitude only, with limit of 200meters(admittedly somewhat arbitrary)
4 No
5- Yes if it is an identified conflict.
6- Provide whatever ID the other glider is using. With ID's suppressed for tactical purposes, I think more pilots would be likely to make them available for conflict resolution.
7- Yes. To me this is the greatest shortcoming of existing Stealth. This is a double sided problem to solve. Plus- it provides little if any degradation of safety for other stake holders. This factor was the principle reason why the BGA stopped the Stealth mandate over there. Negative- it is much harder to ensure that the new mode performs equally for all without hackers turning it wide open again. This would require use of flight displays running programs shown to be compliant. Nothing is without complication. The other negative is that it could enable ground tracking . Possibly the privacy settings could prevent this.
8- I don't have enough visibility into how effective ADSB information will be tactically compared to Flarm to have an opinion. From a tactical point of view, I'd love it to be not there at all. From a safety point of view, I'd like it to be effective.
Again- Thanks for fostering a constructive exchange.
UH
I think we can find a common ground on a number of points:
(1), (2), (4), (5), (6), (7)
In regards to (3) I would suggest we increase the 200 meters and this is why. Flying in Ely, NV I learned that I can gain or lose 200 meters is just 20 seconds flying straight. I almost busted class A once.
Let's consider this closely:
We have two gliders flying in opposite directions. One glider gains altitude the other loses altitude. The other glider may all of the sudden appear on your display say 1 km in front of you with 200 meters of vertical separation (very difficult to see). You would be left with just 10 seconds to avoid collision.

The 5 km of horizontal distance gives us about 37 seconds of warning. We need to come up with the same 37 seconds of warnings for vertical separation.

Let's consider an edge case both gliders change altitude 10 m/s each, quite possible in western conditions. This gives you 20 m/s combined vertical closure speed. If you want to obtain reaction time of 37 seconds (same as for the 5 km distance) you need 720 meters of separation. That means you need to be able to see traffic that is either 2000 feet above you or below you (I rounded the number down). Of course any lower number would be problematic. I hope you agree with this reasoning.

Now the hard part (8), the information that ADS-B provides can be utilized to show whatever one wants with the right smart phone software. The only way to restrict that would be to run approved displays. In the USA however all ADS-B in solutions that are useful are provided by companies that have nothing to do with gliding.

One option I see is that PowerFlarm upgrades software of their unit to ensure proper reception of ground station information (if there is enough processing power within the unit to deal with both ground station broadcast and Flarm functions). Then display manufacturers could filter traffic the same way as they would do for gliders. With the exception of traffic moving faster than e.g. 150 kts where no filtering would take place. That leaves us with a case where there is not enough ground station coverage (west) and where 978 Mhz band is useful to identify traffic equipped with ADS-B out UAT. Maybe PF units could be upgraded, difficult to say.

Maybe a better solution would be for someone e.g. LXNav or Flarm to create a receiver for both 1090 Mhz and 978 Mhz frequencies that could be configured to restrict output in the same way as with the new mode that we described above.

This is a tough nut to crack and it also limits choices for buyers so a solution would need to be very well priced. An open source project is another opportunity but it would require someone to start it and push forward. The hardware is there but there is still a problem integrating the devices to common display. This is doable but not simple, especially for the market of our size. Although ADS-B In solution that is well priced might be something that many more pilots could get interested in.

Let's keep this thread technical.



--
Dan, 5J

On Wednesday, January 6, 2016 at 7:36:27 AM UTC-8, Dan Marotta wrote:
In the spirit of technical discussion I must point out what seems to
me to be a basic flaw in logic.



The statement that you can gain or lose altitude at 10 m/s (~20 kt)
is certainly valid in the US southwest.* However the supposition
that two gliders traveling in opposite directions with 200 meter
vertical separation would be at risk of collision due to one
suddenly dropping and the other suddenly climbing in the same
airmass does not appear to be a serious risk.* To do
this would require one or both of the gliders to pull up in sink or
push over in lift.* In reality both would either pull up or push
over thus keeping the vertical separation nearly the same.



As to the stealth argument, if only ID and (claimed) climb rate are
masked, with position and relative altitude still displayed, where's
the loss in situational awareness?* Remember that there are still
right of way rules to follow to avoid swapping paint.



Someone mentioned the danger of one glider pushing over to leave a
thermal as another is pulling up into the same thermal.* This is a
valid concern, though a special case.* Assuming both aircraft are
equipped with some sort of anti-collision device then a maintained
situational awareness should preclude any abrupt maneuvers in close
proximity to another glider.* I realize that some folks have a "get
out of my way" philosophy and no device can be expected to keep them
from doing something unexpected.




On 1/5/2016 3:56 PM, Andrzej Kobus
wrote:



On Tuesday, January 5, 2016 at 9:02:51 AM UTC-5, wrote:


On Monday, January 4, 2016 at 6:08:40 PM UTC-5, Andrzej Kobus wrote:


I think it is time to end this back and forth ping pong about restricting the use of PF. We have to agree to disagree and try to come up with a solution that could work for both groups.
Let's try to define some criteria that might be acceptable to all:
1) Should targets be visible on PowerFlarm display?
2) If (1) is "Yes" then what is the desired distance at which targets should be visible on PowerFlarm display?
3) Do we allow for displaying altitude of another glider on PowerFlarm display?
4) Do we allow for displaying information pertaining to climb rate or simply indicate if a glider is ascending or descending?
5) Do we need to be able to identify a conflicting glider?
6) What are the minimum requirements for identification of conflicting traffic?
7) Should we aim not to degrade PF functions for non-contest participating PF users in the area of a contest?
8) How do we deal with ADS-B in a glider? I have ADS-B out plus I have ADS-B in on both 1090 and 978.
9) Anything else?




In the interest of having a constructive discussion on the topic- THANK YOU ANDRZEJ!, I will provide my personal opinions.
1- Yes
2- I have suggested 5km previously
3- Relative altitude only, with limit of 200meters(admittedly somewhat arbitrary)
4 No
5- Yes if it is an identified conflict.
6- Provide whatever ID the other glider is using. With ID's suppressed for tactical purposes, I think more pilots would be likely to make them available for conflict resolution.
7- Yes. To me this is the greatest shortcoming of existing Stealth. This is a double sided problem to solve. Plus- it provides little if any degradation of safety for other stake holders. This factor was the principle reason why the BGA stopped the Stealth mandate over there. Negative- it is much harder to ensure that the new mode performs equally for all without hackers turning it wide open again. This would require use of flight displays running programs shown to be compliant. Nothing is without complication. The other negative is that it could enable ground tracking . Possibly the privacy settings could prevent this.
8- I don't have enough visibility into how effective ADSB information will be tactically compared to Flarm to have an opinion. From a tactical point of view, I'd love it to be not there at all. From a safety point of view, I'd like it to be effective.
Again- Thanks for fostering a constructive exchange.
UH


I think we can find a common ground on a number of points:
(1), (2), (4), (5), (6), (7)
In regards to (3) I would suggest we increase the 200 meters and this is why. Flying in Ely, NV I learned that I can gain or lose 200 meters is just 20 seconds flying straight. I almost busted class A once.
Let's consider this closely:
We have two gliders flying in opposite directions. One glider gains altitude the other loses altitude. The other glider may all of the sudden appear on your display say 1 km in front of you with 200 meters of vertical separation (very difficult to see). You would be left with just 10 seconds to avoid collision.

The 5 km of horizontal distance gives us about 37 seconds of warning. We need to come up with the same 37 seconds of warnings for vertical separation.

Protocol - it's there for a reason. I understand coordinating in a
thermal, e.g., "BD, I'm inside your turn at 5 o'clock low", but calling
someone almost a mile away and suggesting that he make a turn so as not
to collide with me when I can simply make my own turn doesn't make sense.

Do you really need information on another aircraft within 300 meters
vertical spacing from you? That's almost 1000 feet! IFR and VFR
traffic routinely pass each other head on, over taking, and at oblique
angles with only 152 meters (500') vertical separation. I can
understand your concerns in and around thermals, but not in cruise.


On 1/6/2016 10:13 AM, jfitch wrote:
On Wednesday, January 6, 2016 at 7:36:27 AM UTC-8, Dan Marotta wrote:
In the spirit of technical discussion I must point out what seems to
me to be a basic flaw in logic.



The statement that you can gain or lose altitude at 10 m/s (~20 kt)
is certainly valid in the US southwest. However the supposition
that two gliders traveling in opposite directions with 200 meter
vertical separation would be at risk of collision due to one
suddenly dropping and the other suddenly climbing in the same
airmass does not appear to be a serious risk. To do
this would require one or both of the gliders to pull up in sink or
push over in lift. In reality both would either pull up or push
over thus keeping the vertical separation nearly the same.



As to the stealth argument, if only ID and (claimed) climb rate are
masked, with position and relative altitude still displayed, where's
the loss in situational awareness? Remember that there are still
right of way rules to follow to avoid swapping paint.



Someone mentioned the danger of one glider pushing over to leave a
thermal as another is pulling up into the same thermal. This is a
valid concern, though a special case. Assuming both aircraft are
equipped with some sort of anti-collision device then a maintained
situational awareness should preclude any abrupt maneuvers in close
proximity to another glider. I realize that some folks have a "get
out of my way" philosophy and no device can be expected to keep them
from doing something unexpected.




On 1/5/2016 3:56 PM, Andrzej Kobus
wrote:



On Tuesday, January 5, 2016 at 9:02:51 AM UTC-5, wrote:


On Monday, January 4, 2016 at 6:08:40 PM UTC-5, Andrzej Kobus wrote:


I think it is time to end this back and forth ping pong about restricting the use of PF. We have to agree to disagree and try to come up with a solution that could work for both groups.
Let's try to define some criteria that might be acceptable to all:
1) Should targets be visible on PowerFlarm display?
2) If (1) is "Yes" then what is the desired distance at which targets should be visible on PowerFlarm display?
3) Do we allow for displaying altitude of another glider on PowerFlarm display?
4) Do we allow for displaying information pertaining to climb rate or simply indicate if a glider is ascending or descending?
5) Do we need to be able to identify a conflicting glider?
6) What are the minimum requirements for identification of conflicting traffic?
7) Should we aim not to degrade PF functions for non-contest participating PF users in the area of a contest?
8) How do we deal with ADS-B in a glider? I have ADS-B out plus I have ADS-B in on both 1090 and 978.
9) Anything else?




In the interest of having a constructive discussion on the topic- THANK YOU ANDRZEJ!, I will provide my personal opinions.
1- Yes
2- I have suggested 5km previously
3- Relative altitude only, with limit of 200meters(admittedly somewhat arbitrary)
4 No
5- Yes if it is an identified conflict.
6- Provide whatever ID the other glider is using. With ID's suppressed for tactical purposes, I think more pilots would be likely to make them available for conflict resolution.
7- Yes. To me this is the greatest shortcoming of existing Stealth. This is a double sided problem to solve. Plus- it provides little if any degradation of safety for other stake holders. This factor was the principle reason why the BGA stopped the Stealth mandate over there. Negative- it is much harder to ensure that the new mode performs equally for all without hackers turning it wide open again. This would require use of flight displays running programs shown to be compliant. Nothing is without complication. The other negative is that it could enable ground tracking . Possibly the privacy settings could prevent this.
8- I don't have enough visibility into how effective ADSB information will be tactically compared to Flarm to have an opinion. From a tactical point of view, I'd love it to be not there at all. From a safety point of view, I'd like it to be effective.
Again- Thanks for fostering a constructive exchange.
UH


I think we can find a common ground on a number of points:
(1), (2), (4), (5), (6), (7)
In regards to (3) I would suggest we increase the 200 meters and this is why. Flying in Ely, NV I learned that I can gain or lose 200 meters is just 20 seconds flying straight. I almost busted class A once.
Let's consider this closely:
We have two gliders flying in opposite directions. One glider gains altitude the other loses altitude. The other glider may all of the sudden appear on your display say 1 km in front of you with 200 meters of vertical separation (very difficult to see). You would be left with just 10 seconds to avoid collision.

The 5 km of horizontal distance gives us about 37 seconds of warning. We need to come up with the same 37 seconds of warnings for vertical separation.

Let's consider an edge case both gliders change altitude 10 m/s each, quite possible in western conditions. This gives you 20 m/s combined vertical closure speed. If you want to obtain reaction time of 37 seconds (same as for the 5 km distance) you need 720 meters of separation. That means you need to be able to see traffic that is either 2000 feet above you or below you (I rounded the number down). Of course any lower number would be problematic. I hope you agree with this reasoning.

Now the hard part (8), the information that ADS-B provides can be utilized to show whatever one wants with the right smart phone software. The only way to restrict that would be to run approved displays. In the USA however all ADS-B in solutions that are useful are provided by companies that have nothing to do with gliding.

One option I see is that PowerFlarm upgrades software of their unit to ensure proper reception of ground station information (if there is enough processing power within the unit to deal with both ground station broadcast and Flarm functions). Then display manufacturers could filter traffic the same way as they would do for gliders. With the exception of traffic moving faster than e.g. 150 kts where no filtering would take place. That leaves us with a case where there is not enough ground station coverage (west) and where 978 Mhz band is useful to identify traffic equipped with ADS-B out UAT. Maybe PF units could be upgraded, difficult to say.

Maybe a better solution would be for someone e.g. LXNav or Flarm to create a receiver for both 1090 Mhz and 978 Mhz frequencies that could be configured to restrict output in the same way as with the new mode that we described above.

This is a tough nut to crack and it also limits choices for buyers so a solution would need to be very well priced. An open source project is another opportunity but it would require someone to start it and push forward. The hardware is there but there is still a problem integrating the devices to common display. This is doable but not simple, especially for the market of our size. Although ADS-B In solution that is well priced might be something that many more pilots could get interested in.

Let's keep this thread technical.







--

Dan, 5J
Climb rate is already effectively masked by Flarm, since it is so wildly inaccurate as to be fantasy. ID masking eliminates the possibility of calling the other glider, and this is most useful at longer range. You are not going to reliably call another glider, receive a response, negotiate a passing protocol, then execute it in 10 seconds. But if something has to be done, then in my view climb rates could go easily (they do not really exist now, so that is a no op). The next thing I would miss least is relative altitude, if greater than (pick a number). That potentially carries tactical information. If they are within 300 meters altitude or so I would like to know, for situational awareness. Contest ID, is useful at 60+ seconds out to discuss intentions (though I do this rarely with good situational awareness) ID is useful close in to match alerts/warnings with sailplanes, when the sky is crowded. For example flying in a thermal with 3 other gliders I may get (expected) alerts about them. If a 4th joins, I might mistake an alert from it for an expected one (the false positive test problem) - but would not if all are displayed and identified on screen. Still I would see 4 gliders instead of the previous 3, so to a great extent SA is preserved.

--
Dan, 5J

On Wednesday, January 6, 2016 at 7:36:27 AM UTC-8, Dan Marotta wrote:
In the spirit of technical discussion I must point out what seems to
me to be a basic flaw in logic.



The statement that you can gain or lose altitude at 10 m/s (~20 kt)
is certainly valid in the US southwest.* However the supposition
that two gliders traveling in opposite directions with 200 meter
vertical separation would be at risk of collision due to one
suddenly dropping and the other suddenly climbing in the same
airmass does not appear to be a serious risk.*

I think the idea is that they'd be in *different*, adjacent airmasses. Where you have strong lift you tend to have similar sink adjacent to the lift, this is true for wave, convergence and thermals. It's one reason why it's common to push over when exiting a thermal, so you can quickly traverse the sinking air surrounding the thermal (what goes up comes down somewhere nearby - that way all the air doesn't end up above the boundary layer). I've gained 1,000' pulling up in strong lift and I've seen similar opposite situations thunderstorm shelf-running. The climbing and descending gliders would not be maneuvering in the same thermal to be sure as it's hard to imagine in that case the pushing over into sink glider and the pulling up in lift glider doing anything other than diverging, but one glider pushing over to get through a veil of rain and sink while another glider is just pulling up into the strong lift under the shelf just beyond. You'd like to see that guy coming rather then letting him sneak in below the Stealth invisibility cloak and pop up into a conflict. Maybe it's just me, but I don't like surprises.

Part of the challenge with selectively degrading a device like Flarm is making sure you haven't made an assumption about the scenarios that can (or can't) come up.

9B

On Thursday, January 7, 2016 at 6:20:32 PM UTC-8, Andy Blackburn wrote:
On Wednesday, January 6, 2016 at 7:36:27 AM UTC-8, Dan Marotta wrote:
In the spirit of technical discussion I must point out what seems to
me to be a basic flaw in logic.



The statement that you can gain or lose altitude at 10 m/s (~20 kt)
is certainly valid in the US southwest.* However the supposition
that two gliders traveling in opposite directions with 200 meter
vertical separation would be at risk of collision due to one
suddenly dropping and the other suddenly climbing in the same
airmass does not appear to be a serious risk.*

I think the idea is that they'd be in *different*, adjacent airmasses. Where you have strong lift you tend to have similar sink adjacent to the lift, this is true for wave, convergence and thermals. It's one reason why it's common to push over when exiting a thermal, so you can quickly traverse the sinking air surrounding the thermal (what goes up comes down somewhere nearby - that way all the air doesn't end up above the boundary layer). I've gained 1,000' pulling up in strong lift and I've seen similar opposite situations thunderstorm shelf-running. The climbing and descending gliders would not be maneuvering in the same thermal to be sure as it's hard to imagine in that case the pushing over into sink glider and the pulling up in lift glider doing anything other than diverging, but one glider pushing over to get through a veil of rain and sink while another glider is just pulling up into the strong lift under the shelf just beyond. You'd like to see that guy coming rather then letting him sneak in below the Stealth invisibility cloak and pop up into a conflict. Maybe it's just me, but I don't like surprises.

Part of the challenge with selectively degrading a device like Flarm is making sure you haven't made an assumption about the scenarios that can (or can't) come up.

9B

Some people do push over in lift, and nearly everybody pulls up in lift. If you are near cloud base in a thermal and you expect sink in the ring around it (very common), a correct strategy is to turn sharply 180 degrees from the intended departure direction and dive through the core so that you have maximum speed gain with minimum loss to traverse the sink. This is exactly when a glider entering is pulling up. 1000 ft is nothing in this scenario.

On Tuesday, January 5, 2016 at 6:02:51 AM UTC-8, wrote:
On Monday, January 4, 2016 at 6:08:40 PM UTC-5, Andrzej Kobus wrote:
I think it is time to end this back and forth ping pong about restricting the use of PF. We have to agree to disagree and try to come up with a solution that could work for both groups.
Let's try to define some criteria that might be acceptable to all:
1) Should targets be visible on PowerFlarm display?
2) If (1) is "Yes" then what is the desired distance at which targets should be visible on PowerFlarm display?
3) Do we allow for displaying altitude of another glider on PowerFlarm display?
4) Do we allow for displaying information pertaining to climb rate or simply indicate if a glider is ascending or descending?
5) Do we need to be able to identify a conflicting glider?
6) What are the minimum requirements for identification of conflicting traffic?
7) Should we aim not to degrade PF functions for non-contest participating PF users in the area of a contest?
8) How do we deal with ADS-B in a glider? I have ADS-B out plus I have ADS-B in on both 1090 and 978.
9) Anything else?


In the interest of having a constructive discussion on the topic- THANK YOU ANDRZEJ!, I will provide my personal opinions.
1- Yes
2- I have suggested 5km previously
3- Relative altitude only, with limit of 200meters(admittedly somewhat arbitrary)
4 No
5- Yes if it is an identified conflict.
6- Provide whatever ID the other glider is using. With ID's suppressed for tactical purposes, I think more pilots would be likely to make them available for conflict resolution.
7- Yes. To me this is the greatest shortcoming of existing Stealth. This is a double sided problem to solve. Plus- it provides little if any degradation of safety for other stake holders. This factor was the principle reason why the BGA stopped the Stealth mandate over there. Negative- it is much harder to ensure that the new mode performs equally for all without hackers turning it wide open again. This would require use of flight displays running programs shown to be compliant. Nothing is without complication. The other negative is that it could enable ground tracking . Possibly the privacy settings could prevent this.
8- I don't have enough visibility into how effective ADSB information will be tactically compared to Flarm to have an opinion. From a tactical point of view, I'd love it to be not there at all. From a safety point of view, I'd like it to be effective.
Again- Thanks for fostering a constructive exchange.
UH

Andrzej must build bridges for a living.

Replying to two different topics raised in this thread.

1) Yes
2) I'd consider 5km bare minimum as the "Situational Awareness Crowd" out west will be heads down more frequently street-running with as little as 35-40 seconds of forward visibility - scanning the screen every 20 seconds is a bit high. It would be preferable to have a bit more.
3,4) Relative altitude +/-750 meters - high altitude zooms and pushes are a lot more than 200m when done in opposition - plus opposite lift/sink. Having someone pop into your SA zone from below right when you are rolling out of a thermal and pushing over - hard to deal with.
5,6) Flarm ID plus FlarmNet ID if available for conflicts. Flam ID is next to useless for making contact for converging multi-ship situations - if having stealth allow us to require FlarmNet for safety reasons, so much the better.
7) This can't be allowed in any future incarnation of stealth - too much other traffic want 5 mile separation and can be coming in a lot hotter than glider speeds if it gets deployed in jets (mostly a European/UK issue for now - but it's one code base). Also, subjecting the uninitiated to Stealth mode without their knowledge or any briefing is a really bad idea - among other things it makes it harder to stay out of the way of the gaggle, etc.
8) Honestly I think ADS-B is hopeless in terms of implementing any kind of stealth mode. It would involve trying to coordinate the efforts of too many OEMs, may have regulatory implications if the glider exemption falls (as it seems likely to), won't deal with TIS-B Mode C traffic at all and might require burdensome racing-only approved equipment lists. Plus unless the exact Flarm algorithm is used on a combined dataset of ADS-B plus Flarm traffic you'll never be able to dedup the traffic leading to ghosting, multiple alarms - makes my head spin. Ultimately, ADS-B puts an end to any practical stealth implementation without draconian equipment restrictions and intractable technical difficulties - and is even more certain with an end to the glider exemption for transponders and/or ADS-B Out.

I am 99.9% certain that it is impossible for Flarm Stealth to be implemented on the transmit side. IIRC, part of the collision algorithm involves projected position estimates performed on the transmit side and sent to all receivers for comparison with each internal projected position. You can't perform collision warning without this information and stealth would cut it out if done pre-transmission. Without a way to estimate whether a target is a collision conflict to pass it through to the collision display you need both received and local position estimates. Since the Flarm documentation clearly states that alarms can be generated outside the stealth 2km traffic radius it's just logically impossible for this to happen based on data that is cut off before being transmitted.

If you want to chase your tail logically, ask yourself if position data could be transmitted only for collision threats but not for non-threats. Answer: What if everybody did that?

BTW, someone needs to confirm how far out Flarm projects future position for collision warning - I thought I remembered 15 seconds from some conversation. If so, that would presumably be the maximum collision threat advanced warning you'd get under stealth unless you had more range on the traffic display side.

9B

Since the paranoia seems to surround the theoretical possibility of Flarm leeching, here is a suggestion: I believe you may be able to determine leeching (provided someone can define it) by using the Flarm IGC file. In it are comment lines which enumerate each Flarm contact. I'm not sure if I am decoding these correctly but it seems as though the received Flarm is identified uniquely. To leech in the way that is the source of the paranoia, one would need to keep in Flarm contact throughout the day. This should be quite apparent from an analysis of the contact comments, perhaps in combination with the position reports to see who is leading and who trailing. Some definition of leeching would need to be proposed based on leading/following, % time in contact, etc. There is no information there that is not already contained in the relevant IGC position data, but it is easier to process, and adds proof that the target of the leech was in Flarm contact (which must be part of any Flarm leeching by definition).

Note that the same thing can be done for ADS-B, at least with Mode S transponders and a PowerFlarm log. It would flag visual leeching as well, since visual leeching is a subset of Flarm leeching.

All this appears to be technically feasible, except perhaps for the definition of leeching which has so far been elusive. The log checking can be an automated part of the scoring process, or applied in the event of a protest.

On Tuesday, January 5, 2016 at 12:36:54 PM UTC-5, jfitch wrote:
Since the paranoia[...]

Can we please have just one flarm-in-competition thread that is constructive? Enough of the loaded comments, goading and scare mongering!

UH: all filtering occurs on receiving end. It has to be this way, else anti-collision warning performance would be compromised.

T8

On Tuesday, January 5, 2016 at 3:21:30 PM UTC-5, Tango Eight wrote:
On Tuesday, January 5, 2016 at 12:36:54 PM UTC-5, jfitch wrote:
Since the paranoia[...]

Can we please have just one flarm-in-competition thread that is constructive? Enough of the loaded comments, goading and scare mongering!

UH: all filtering occurs on receiving end. It has to be this way, else anti-collision warning performance would be compromised.

T8

Does the Flarm info I showed above not disagree with what you just stated?, and if not, please help me understand why.
Additionally, if info out is not changed, why does my use of Stealth affect what others not using Stealth see related to me?
Thx
UH

Additionally, if info out is not changed, why does my use of Stealth affect what others not using Stealth see related to me?


If your FLARM is set to STEALTH it will not show all the info it receives on your display regardless of source. The STEALTH FLARM sends a message out telling other FLARM units that you are in STEALTH. When another unit sees this as part of the message it will not display your information on their own display.

Luke Szczepaniak