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TCAS registers reporting dupes when range 'limited'


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Hi Peter!

I'm working on a AI smoothing process that evaluates incoming flights into "my" arrival ICAO. While successfully retrieving information from the F080-FF7E TCAS registers, I noticed that these registers report "duplicate" AI flights (i.e. looking a the Flight#) when the FSUIPC TCAS range is set to 'some' limit. However, when it is set to 'unlimited' it no longer reports dupes.

I verified this using FSInterrogate2. Obviously we can work around the problem by setting the range to unlimited, but I thought you should be made aware of this issue if you have not already.

Also, these dupes aren't exact dupes, the Longitude and Latitude, as well as other flight atritbutes, of the apparent duplicate Flight#s differ. Would seem to indicate that 'some' other flight is being detected, but the incorrect Flight# is being assigned to that register. (Just some extra info that might help)

Great product Peter!!! Thanks for all your hard work!

Cheers,

Phil (registered user)

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I noticed that these registers report "duplicate" AI flights (i.e. looking a the Flight#) when the FSUIPC TCAS range is set to 'some' limit. However, when it is set to 'unlimited' it no longer reports dupes.

I've not seen this, nor do I know how it is possible. The range check merely determines whether an entry will be made or not.

I verified this using FSInterrogate2.

Can you show me? Don't go by Flight#, please check only the IDs. Slots where the ID is zero are free -- you must then ignore the rest of the data.

If you want to send me some evidence do so via petedowson@btconnect.com, but please double check these things first. The TCAS data provided is actually range limited by default and has been provided, virtually unchanged now, for well over three years, and I've never seen a duplicate in, for instance, TrafficLook, which simply displays everything it sees.

It really does sound as if you are not checking the main "slot used" indicator, the ID, the first entry in the structure.

Maybe what is happening with a range set is that some aircraft are going in and out of range, therefore appearing and disappearing and reappearing. They will likely get different slots each time they reappear.

Regards

Pete

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Peter,

Very strange... I rebooted FS2004 and restarted all the periperal apps that integrate with it and I can't get this issue to reappear.

I've been working on this application for AI smoothing for a couple of days now and this was the first shutdown of FS that I've done -- mostly because I've been developing this eventual freeware app and testing it. I hadn't needed to shutdown FS.

I'm wondering if, by aggressively restarting different "flights" to try different aiport scenarios as well as different traffic densities, that I tripped some condition that causes this situation.

Funny how it appeared last night and stayed consistent this morning. Once I removed the range limitation and solved the 'alleged' problem, I was contented, then posted to your forum what I found... then shutdown the application to take a break. There went the evidence! Grrrrr

Obviously, if I tripped it in my aggressive switching between flights or any other way, the chances are extremely remote that anyone will see this in a regular user environment.

Frustrating when I spent sooo many hours trying to understand the issue so I could let you know... and try to find a work-around.

If I see any strange behavior like this again, I will be more congnizant of what I may have done to introduce it and let you know.

Best to you Peter! And Happy New Year!

Phil

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I'm wondering if, by aggressively restarting different "flights" to try different aiport scenarios as well as different traffic densities, that I tripped some condition that causes this situation.

Well obviously that will make AI aircraft come and go a lot more, so the slots will get used, freed, used again and so on, but then yje 'range' business wouldn't have any beneficial effect.

Can you please confirm that you are checking the "id" field", not just the flight number as you mentioned. It is the Id field which defines a slot's usage -- you must not use information in a slot with a zero id.

Regards

Pete

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Yes, I am using the "id" field.

When I witnessed the strange behavior even valid airborne flights (visible in FS) were showing up in FSInterrogate with the id field as 0x00000000. In some duplication cases both flights had 0x00000000, and some cases both had apparently valid (and duplicate) id's, while still some times flights that were duplicated had 0x00000000 while it's alter-ego (same Flight#) had an apparently valid id.

As you can see, I started losing trust in the "id" field (and losing my mind!). Too many possible id combinations, with no logical way to know which one was right/wrong, valid or invalid. I simply used the Flight# as a visual queue when Interrogating the registers because of this id dilemma.

So far, since my last post... I did have dupes show up again, but failed to re-enact the chain of events that caused it.

If I can come up with a predictable, reconstructable chain of events, with some supporting evidence, I will let you know. I'd rather not just give you just the Interrogated data that shows duplicates, I'd like to give you the events that cause it because I don't want to waste your time any more than I already have.

Thanks again!

Phil

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When I witnessed the strange behavior even valid airborne flights (visible in FS) were showing up in FSInterrogate with the id field as 0x00000000. In some duplication cases both flights had 0x00000000, and some cases both had apparently valid (and duplicate) id's, while still some times flights that were duplicated had 0x00000000 while it's alter-ego (same Flight#) had an apparently valid id.

A zero ID field most definitely means that slot is now unused -- I simply don't bother to clear the rest of the structure as it is a waste of processing when the ID is the 'key'.

As you can see, I started losing trust in the "id" field (and losing my mind!). Too many possible id combinations, with no logical way to know which one was right/wrong, valid or invalid.

The logical way is to stick to the documented rules -- zero in the Id field means that slot is not used. Always, no exceptions.

I'd rather not just give you just the Interrogated data that shows duplicates, I'd like to give you the events that cause it because I don't want to waste your time any more than I already have.

I do not want to see anything showing zero Ids being treated as valid slots. They are not. Please change your methods.

Regards

Pete

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Pete,

Understood... totally!

I'm just telling you that I "witnessed" airplanes flying in the sky that had invalid id's (0's) in the TCAS structure. :shock: During this time it was very frustrating to see that I was not getting those planes in my list of AI flights... because I *was* ignoring '0' value id's. That's what started this whole chase last night. It baffled me that I saw planes flying (captioned in red, by FS) less than 10nm from me... but those planes were not in my list. But they were in FSInterrogate with 0 id's -- which confused me. It clarified for me "why" I don't put them in my list (I followed you rules!), but now I needed to know "why" they are still flying out there with a "0" id. That's when I started seeing duplicate entries of the nature I previously described.

As I said... when I restarted FS all that confusion went away.

Be certain... I have a very STRICT check so that I do ignore '0' value id's. You made that perfectly clear in your detailed AI section of the programmer's doc.

There's nothing wrong with my methods, I'm just sharing what I'm seeing. Things that aren't consistent with what you documented... but things that are likely caused by conditions of constantly switching between different flight scenarios over the course of time. I think that under "normal" use this problem would never be seen.

Phil

p.s. I am traveling on business Monday and won't be back until Friday to work on this project. I will check the forum, but won't have access to my cockpit until next week. My apologies that I might vanish for a day or so.

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