Skyview!


#1

Hello all, I have seen that sometimes I can see that my feeder has detected an aircraft and I can even see a flag of the plane that is being detected but I don’t see its icon within the radius, Please clarify this to me, why?


#2

Not all aircraft broadcast their position.

So if an aircraft is not ADS-B equipped you will receive it’s altitude and maybe some other data but not its location.
You can still click on the row in the table to get some more details.

You can read
(https://en.wikipedia.org/wiki/Aviation_transponder_interrogation_modes)
or maybe a shorter and more relevant writeup
(https://shop.jetvision.de/Blog/What-actually-is-Mode-A/C-Mode-S-and-ADS-B)
if you are interested.


#3

Also, if in your receiving area would be 4 receivers, with MLAT enabled, that are seeing that plane simultaneously, then it would appear on the map, because FA will be able to triangulate the position.


#4

Not necessarily true.
For the receivers to be synchronized you need a few ADS-B aircraft also in range of all participating receivers to synchronize off their signals.
Maybe flightfeeders don’t need that though as they have a GPS clock i believe. Not sure.


#5

Yes, they need to have the location set (timing is derived individually from the ADS-B signal). Around him are all FlightFeeders (equipped with GPS in that world region), I have looked already in that on the other thread:


#6

Thank you, I am still new at understanding the way these stuffs work, I apologize if you find me a complete noob, but I will eventually get better some days :slight_smile:


#7

Yeah, you should apologize for being a noob, as opposed to us, geniuses, that where born knowing all this stuff :rofl:

Seriously now, it’s a learning experience for all of us on this forum, more or less. Only when you don’t know anything, you don’t realize that… you don’t know.
To me, the more I get informed in one domain, the more I realize how much is there to learn! That’s part of the fun!


#8

No that was not what i was saying.

As you can see in his screenshot there is only on plane being received.

Now even if there were 4 receivers receiving that plane they could not determine a position.
(Unless they all have GPS clocks and those are used to synchronize them but i’m not sure how if that is implemented)

Normally synchronization is achieved using ADS-B messages from planes broadcasting their position.


#9

They might be using GPS sync, regular piaware is not, it uses ntp servers.
However, as I understand the MLAT, the software has adaptive timing that allows for slightly different clocks, if the delta is stable.


#10

The regular system clock is synchronized with ntp to get in the right ballpark.
NTP is not precise enough for multilateration, neither is the system clock.

The actual synchronization is on the 12MHz dongle clock which the messages all get a sequential timestamp from.
This synchronization will only last a relatively short time, not sure exactly how long.
That’s the reason the mlat servers send out a selection of ADSB messages with known position which serve as a pseudo clock after the individual receiver check with timestamp those messages had on their clock.

Instead of this synchronization over common ADSB messages you can use the GPS clock but only if the GPS clock is integrated into the receiving device. A USB connected GPS clock for example would not help.

So without common ADSB signals MLAT won’t work without specialized receivers.


#11

Yeah… I don’t know how the GPS is connected in the FF that he has. I assume is not via USB.
My Orange FF doesn’t have GPS.
IMO the newer blue FlightFeeders use this BeastS board:

The Trimble 97975-05 is a GPS timing receiver:


#12

Yes i use newer feeder with this same board exactly