Primarily for general aviation discussion, but other aviation topics are also welcome.
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#1664734
Straight Level wrote:
Ian Melville wrote:SkyEcho cannot receive OGN/R rebroadcasts. Also, Gaznav has clearly stated that they are ADS-B. OGN/R only rebroadcasts Mode-S so is not a factor.


OGN also rebroadcasts FLARM ;-)...but you knew that already :-)


You are correct, I wasn't thinking of that side of the system as the discussion is not about FLARM position accuracy. I will correct my post
gaznav, Straight Level liked this
User avatar
By gaznav
#1664744
I had another grand day out with a borrowed FLARM and formation with a mate in his Skybolt - both of us with SkyEcho 2s. He could see my FLARM at around 5nm most of the time - so, again, as aircraft to aircraft, that is good enough for me (and that is the normal detection range for FLARM to FLARM).

I had a look at the PA28’s stack and it looked like it has Garmin GTX ES transponder. The Ops Manager wasn’t about so I couldn’t see much more. However, I saw another couple of aircraft today that were of interest. The first was a Twin Commanche that had no red circle around it:

Image

Again I saw the aircraft and it was exactly where it was showing on SkyDemon.

Later on, whilst flying around with the Skybolt (SBOL) then I could see his SkyEcho 2 with no circle around it. But a 2nm circle around a Cessna 182 at Turweston (at first I thought they had their ATZ back!!!) sitting at the hold for Rwy 27.

Image

I then watched it take off with the same 2nm circle around it. Again, this is a certified EASA Cessna 182 and so I was surprised that it was not reporting a better position quality (just like the others that I had seen over the last few days).

Image

I still can’t see how this is a SkyEcho issue as I saw a Twin Commanche displaying normally, a Skybolt displaying its position normally via its SkyEcho 2 and now another certified aircraft displaying this red circle of uncertainty.

Finally, another first today. One of the Forumites asked how SkyEcho 2 performs during aerobatics. Well I watched the Skybolt fly a series of loops and rolls about 2nm from me and I could see his position and relative height displayed to my SkyDemon display accurately. Obviously, the sample rate is once or twice a second so it didn’t track everything, but I could certainly see there was an aircraft there doing things within a small piece of sky above and below relative to my own aircraft. :thumright:

Anyway, I’m kind of done with flying for the next couple of weeks now whilst the other part of the day job catches up. But I will certainly be keeping a weather eye on others’ experiences with these new ‘circle of uncertainity’ depictions.
Last edited by gaznav on Fri Jan 11, 2019 7:28 pm, edited 1 time in total.
User avatar
By GrahamB
#1664747
Just a thought.

Just because an aircraft is an EASA type doesn’t mean that the ADSB-out is approved. The owner could have just connected the wire between boxes that aren’t at the software levels for certification, and thought no one would notice!

A wild theory, but a possibility.
gaznav, Tim Dawson liked this
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By gaznav
#1664751
GrahamB wrote:Just a thought.

Just because an aircraft is an EASA type doesn’t mean that the ADSB-out is approved. The owner could have just connected the wire between boxes that aren’t at the software levels for certification, and thought no one would notice!

A wild theory, but a possibility.


I agree Graham B, but the previous HMCF 2nm circle, which is an approved mod through the LAA, would seem to point to it being better than connecting a ‘hooky’ wire to the back?

I still think there is something fishy going on with protocols either being transmitted or communicating between GPS/GNSS and transponder. I’m seeing this on a wide variety of types with no common denominator to point at. If I was seeing the circles on all ADS-B then it could point to my receiver and software choice - but I’m not, as I see some with circles and some without. If it was a particular set up - like a particular transponder or device - then I could pin it to that, but it appears to be from various set ups.

I’m kind of stumped by it all :?

It was much better when SkyDemon didn’t display them - the aircraft seemed to appear where they reported their position and everything was rosy!!! :lol:

PS. Just a thought. There was talk about an expanded GDL90 protocol, this isn’t the source of the issue is it?
User avatar
By gaznav
#1664766
Ian Melville wrote:Has there been a recent change to SD? I can see nothing in the change logs.


I couldn’t see that either. But I have a feeling I remember reading about some adaptations of the GDL90 protocol to allow other stuff to be done?
Ian Melville liked this
By patowalker
#1664779
leemoore1966 wrote:
patowalker wrote:But PAW must have been used to verify the accuracy of the position source, in order to get the mod approved by the LAA.

As far as I am aware the only parameters important for the MOD, are SIL and SDA.
Also NACp is not a static setup value, it is a dynamically derived value which changes over time

Thx
Lee


That just shows how tech-savvy I am. :)
User avatar
By Tim Dawson
#1664783
We probably didn’t bother announcing the presence of the circles in the version history. It was probably October ish last year. To be honest, I added them because Lee asked me to (he correctly pointed out the GDL90 protocol asks for us to display a degraded target somehow) and I never thought many people would see them. I find the 10nm uncertainty ring shown earlier in this thread quite worrying.
kanga, leemoore1966 liked this
#1664795
Is it just me or would the red circle thing not logically indicate danger and so proximity to me rather than whether or not its a good signal from the aeroplane concerned??

...have to say not sure I like this aspect, agree with those saying that ATC dont tell you with huge accuracy where other aeroplanes are, and that we should be using these traffic features defensively in the same way - not as a video game.

Regards, SD..

PS: All this tech-speak from some of you is making my head hurt, can we tone it down a little and explain a little more in general terms?
mick w liked this
User avatar
By GrahamB
#1664797
There seems to be a big disconnect here between the actual accuracy of the GPS sources and their reported integrity values, for these outlier targets,

For the most part, they are likely to be using the same source for their own navigation, yet if their own position on their own navigation kit, whether approved IFR navigator or PAW feeding an iPad, was jumping around by up to 10nm five percent of the time, their pilots would notice and take some action.

In a Mode S ES installation the NCAp value is calculated by the transponder based on values passed by the position source. In these installations, either something is getting garbled and it’s an incorrect NCAp value which is being squitted, or displaying the circles of uncertainty is actually misleading and inappropriate, because NCAp means something other than we are interpreting.
#1664798
skydriller wrote:
PS: All this tech-speak from some of you is making my head hurt, can we tone it down a little and explain a little more in general terms?


I was wondering if this should be discussed elsewhere by those with the skillset and tools to investigate this issue rather than a public forum? But on the other hand, you don't have to read it :D
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