Position plots after MLAT data stops

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Martin
Posts: 24
Joined: Wed Jan 14, 2015 9:04 pm
Location: Churchdown, Gloucester

Position plots after MLAT data stops

Post by Martin » Thu Aug 20, 2015 4:30 pm

Hi,

I am working very well with the preview version using merged MLAT data. However, I am very close to a EGBJ and I get a lot of MLAT fixes for flights that approach high and then descend to an altitude where no further MLAT fixes can be made. The last MLAT position then stays on my map until one of three things happens. a) The aircraft flies out of my receiver range, b) The aircraft lands and (eventually) switches off or c) The aircraft climbs back to an altitude where MLAT positions are once again available.

Is it possible to time out the map presentation of an aircraft where no position has been received for a pre-defined period?

Martin

Bhaal
Posts: 37
Joined: Wed Aug 12, 2015 10:20 am

Re: Position plots after MLAT data stops

Post by Bhaal » Sat Aug 22, 2015 3:23 pm

I'd like this also, it's kind of odd seeing one plane fly over another :)

agw
Posts: 2239
Joined: Fri Feb 17, 2012 3:20 am

Re: Position plots after MLAT data stops

Post by agw » Sun Aug 23, 2015 7:41 pm

I uploaded a preview version today that should address this problem - let me know if it doesn't.

Today's preview will stop the web admin plugin from loading. I hadn't bothered to rebuild the web admin plugin as I'm not intending to finish it for the upcoming release, but if you're using it then let me know and I can rebuild it.

Martin
Posts: 24
Joined: Wed Jan 14, 2015 9:04 pm
Location: Churchdown, Gloucester

Re: Position plots after MLAT data stops

Post by Martin » Sun Aug 23, 2015 9:36 pm

Hi Andrew,

I am running the latest preview. Helicopter G-POLA at 1600' over Birmingham was briefly located by MLAT and popped up on the map. Shortly afterwards it disappeared from the map again. Despite not being on the map, the last known position remained populated in the list which is very useful. I am very happy with this.

Thanks,
Martin

Martin
Posts: 24
Joined: Wed Jan 14, 2015 9:04 pm
Location: Churchdown, Gloucester

Re: Position plots after MLAT data stops

Post by Martin » Mon Aug 24, 2015 8:35 am

Just watched OK-RDA coming into GLO from IOM. They appeared with an MLAT position and then a little later dropped off the map as, I presume, MLAT lost it. Then, even though MLAT had picked it up again, I got no new merged positions for this aircraft. Not so happy after all.

Bhaal
Posts: 37
Joined: Wed Aug 12, 2015 10:20 am

Re: Position plots after MLAT data stops

Post by Bhaal » Mon Aug 24, 2015 8:41 am

I am running the new preview, but for me, when my merged feed stops receiving MLAT positions and the timeout on the MLAT feed is reached the plane no longer has the MLAT flag set, but it still stays on the map until the mode-s signal goes out of range from my receiver...

Bhaal
Posts: 37
Joined: Wed Aug 12, 2015 10:20 am

Re: Position plots after MLAT data stops

Post by Bhaal » Mon Aug 24, 2015 9:08 am

Was just thinking a little further about this, if the last position stays in the list it would be really good if when clicked on in the list it could show the plane and it's track to it's last position.. Possible?

Again, Thanks!

Bhaal
Posts: 37
Joined: Wed Aug 12, 2015 10:20 am

Re: Position plots after MLAT data stops

Post by Bhaal » Mon Aug 24, 2015 11:46 am

Alright, weird, I've had MLAT planes drop off, come back, or switch to not being MLAT planes, but still moving etc.. Also, ADS-B planes are falling off before their "position lost" timeout is reached...

agw
Posts: 2239
Joined: Fri Feb 17, 2012 3:20 am

Re: Position plots after MLAT data stops

Post by agw » Sun Aug 30, 2015 6:50 pm

The MLAT value toggling on and off is normal. If you want it to always stay on for MLAT aircraft then you need to get the MLAT source to flag calculated positions as such. The only MLAT message markers that VRS knows about are those added by Oliver Jowett's MLAT server, if you're using Flight Aware's MLAT stuff then I think they used his code. The preview knows about the "00 FF MLAT" magic number timestamp and the "Extended BaseStation" MLAT flags.

If the MLAT source is not flagging calculated positions then the MLAT flag will switch off when the MLAT source becomes the nominated receiver for an aircraft in a merged feed. As far as VRS can tell the nominated feed has positions, and as they're not marked by the source as calculated then it assumes they've been transmitted by the aircraft so the MLAT flag gets switched off.

Martin & Bhaal - what do you have in your configuration for the display timeout (seconds) value and tracking timeout (seconds) values?

Bhaal
Posts: 37
Joined: Wed Aug 12, 2015 10:20 am

Re: Position plots after MLAT data stops

Post by Bhaal » Sat Sep 05, 2015 2:00 am

agw wrote:Martin & Bhaal - what do you have in your configuration for the display timeout (seconds) value and tracking timeout (seconds) values?
My display timeout is 60 seconds, and my tracking timeout is 600 seconds.. I am trying the new version now to see how it goes, sorry for the extended delay in getting back to this.

Regards,
Bhaal

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