Aircraft Reported v Hourly Received


#1

Folks,

On my ads-b data page my ‘Aircraft Reported’ total is considerably less than the Hourly Received Reports showing aircraft.

Maybe I am interpreting this wrong but why the discrepancy?

Geffers


#2

Yes, now you mention it, adding the hourly for the day reveals a much greater number that the total reported in the other graph.

It is indeed odd, and requires quite a bit of explaining. Nice catch.

Let’s hope we get to hear the explanation some time soon.

I do hope that explanation won’t drift too far into the subjunctive mood too. I mean, it can be mildly amusing, but it is not helpful.

Cheers,
Ian


#3

An aircraft is count only once per UTC day(for the daily totals).
The same aircraft is counted only once in the hourly totals.

Say you have a tourist helo(I have dozens). One aircraft will be counted in the hourly totals for each hour it is seen. It will only be counted once in the daily totals.

The same for aircraft that visit daily. I see QF11/12 three or four times a week. In comes in close to the end of the UTC day. I can still see it when it leaves and often that is close to the end of the UTC day. If I see it leave, after the start of the UTC day, it won’t be counted again, for that UTC day, when it returns in the afternoon/ next calendar day for me.


#4

Exactly - the reason that the sum-of-hourly-aircraft is much higher than the daily aircraft total is because you may see the same aircraft during several different hours of the UTC day.


#5

OK, understand the reasoning but I currently have an indoor unit, range not very far, generally see around 1800 aircraft daily.The difference is currently 1400 on today’s (5th September) count, Surely I’m not going to see 1400 aircraft twice or am I totally misunderstanding this?

With my indoor aerial I generally see aircraft approaching London Heathrow but signal poor at that distance.

Geffers


#6

Well, if you are close to Heathrow, each plane that lands will take off again.

A Boeing 737 has a turnaround time of about half an hour, maybe longer until it actually takes off again so chances are high that it will be counted in two different hour segments.

Also, a plane aproaching Heathrow at 13.59 will be counted in the hour from 13:00 to 14:00, two minutes later again in the hour from 14:00 to 15:00. For the whole day it will count as just one unique plane.


#7

Thank you, becoming clearer now.

Really didn’t think the turnaround time was so quick, thought it’d take quite some time to refuel and clean.

The aircraft over my location then I assume will be counted twice at 59 minutes past the hour; this obviously would account for a substantial increase over actual aircraft seen.

Thanks for explanation, learning all the time :slight_smile:

Geffers


#8

Domestic aircraft or budget aircraft (few drinks, meals, pillows and blankets) could probably be turned around fairly quickly. The longer range aircraft (US, Qantas, South american etc) would take longer.
A 30 minute puddle jumper could be counted almost every hour of the day(Depending on use and curfews). Certainly from 6AM-11PM.

Don’t forget we are counting individual transponder codes(unique to aircraft, not routes)
Look at how many times per day you should see this AC