YBBN Something Coming Up At Fire Station

[avostirfry]

Hey Guys,
I think I Have worked out what is coming up at http://fr24.com/-27.39,153.13/17
I think it is the fire Stations Radar dish thingy.

~AvoStirFry

[Oblivian]

We have one that sits ontop of the tower in AKL. And more recently down the south island. Here they are Airways Corp MLAT towers for ATC use.

[Kemistry]

Not sure what you saw and a simple map reference does not allow further investigation (better to post a small screen snip).
Most likely ground vehicles with ADS-B transponders (maybe including firetrucks near their building at YBBN)?
I did request that a different icon be used for ground vehicles so that they are not confused with aircraft - but heard nothing from FR24 guys about this.
See http://forum.flightradar24.com/threa...-traffic-icons

[avostirfry]

I dont think it was a truck, because it was spinning like the radar.

[Kemistry]

I have noticed that spinning symbols are quite common for aircraft (and ground vehicles) when they are on the ground. This rarely happens in the air. I am not sure what sensors are used for heading detection but I believe GPS accuracy is different once the nose wheel is down so suspect heading information on the ground is derived in a different way as well. I also understand that the accuracy of bearing data derived from GPS depends on satellite positions over the vehicle at the time. This has led me to think that heading data in the air is derived from magnetic compass instruments and from GPS calculation when on the ground. Can anyone in the avionics field help clarify this?

Ground vehicles at YBBN seem to have Hex codes 7CF3Dx where I have seen x as 6,7,A and C but there may be others. If you see this again, check the Hex code to see if it’s in this series and let us know.

Incidentally, YBBN does have 4 ADB-B continuous broadcasts that have no positional data so do not get processed by FR24. These Hex codes for these are 7CF7Bx where x is 8,9,A and B. They all send Flight# data of “TEST1234”. Maybe these are the broadcasts that Oblivion has described?

[Traveller]

I note there is a new radar operating near Dunk Island with the alias YDKI-1