Reported speed

[milairuk]

Does VR data show indicated airspeed or ground speed ? Whenever I hear A/C reporting their speed it never agrees with my display, whereas the FL and heading is normally almost spot on ?

John

[jonfear]

Hi John

I think it is ground speed but I am sure Andrew will correct me if I am wrong!

Jon

[milairuk]

Thanks Jon,

Still a bit strange as A/C inbound to EGLL via LAM seem to vary the speed difference reported in VRS even when close to each others altitude and location. I appreciate that at high altitude the IAS will not be correct, but in the descent it should be more accurate. But I'm guessing the ADSB data is GPS derived ??

John

[milairuk]

Yep, it's Ground Speed, been studying the LAM hold and with the strong westerly wind the downwind legs are certainly gaining speed !!

[agw]

It's usually ground speed, although some aircraft will transmit IAS or TAS. I detect the speed type transmitted if you're using a raw feed format and that gets sent to the web site - but I don't actually show it I'll add the display of the speed type to the list of things to do.

[milairuk]

Thanks Andrew, just another one on the list then !! Probably been asked before but could you add the VOR's and possibly NDB's locations to the map ??

Thanks

John