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Comment by photonbucket | Hacker News Reader

What's going on in that part of western australia? It's a very empty area

Grey areas: Few people live there and none have set up a public ADS receiver. And/or no planes flying in the area. https://gpsjam.org/faq/#why-arent-there-red-or-green

Red areas: Military experiments and exercises, probably. https://gpsjam.org/faq/#what-can-cause-aircraft-to-report-lo...

I'm not expert on it, but I suspect that two of them might somehow be related to the Transmit and Receive stations for Australia's JORN (over the horizon radar) that are located in Western Australia near Laverton.

Though if that were the case, I'd probably guess there should be more areas at the other site locations around northern Australia - so that might invalidate my guess.

https://en.wikipedia.org/wiki/Jindalee_Operational_Radar_Net...

https://www.google.com/maps/place/28%C2%B019'02.6%22S+122%C2...

https://www.google.com/maps/place/28%C2%B019'36.3%22S+122%C2...

> What's going on in that part of western australia? It's a very empty area

You answered your own question. Put 2+2 together.

Hint... https://www.flightradar24.com/apply-for-receiver/

I don't live in that country though

> I don't live in that country though

Exactly.

You don't live there.

Not many people live in the Australian desert.

Conclusion: No data or very limited data

Ok, but let's acknowledge the difference between no data (depicted as no colored cell in the map) and data which reports high interference (depicted as a red cell). In remote western Aus we see a few red cells to the west of a large area of empty cells. So they do have ADS-B receivers there, and at least some of them are reporting a troublesome NIC, and there are enough reports for FR24 to place a colored cell there rather than an empty cell. Why exactly do you think that a red cell comes from no data or very limited data, when the article does not indicate that no data / limited data results in a red cell?

"No data" cells are grey on that map, but western Australia has a couple of red ("high interference") cells.

> but western Australia has a couple of red ("high interference") cells.

Erm mate, have you tried looking at different days ? Those cells you find so suspicious in Australia are not there on other days !

Seriously, given the largely community-based nature of FR24 data I would not expect too much in term of accuracy.

> Erm mate, have you tried looking at different days ? Those cells you find so suspicious in Australia are not there on other days !

That kind of disproves the "no data" hypothesis though, no?

One explanation could be they have a simplistic algorithm like "if uncertainty > (something indicating more than 5 minutes of GNSS-to-INS fallback) on more than 50% of all flights of a day", and there's only one flight per day in that region.

> Seriously, given the largely community-based nature of FR24 data I would not expect too much in term of accuracy.

Flightradar24 data is accurate enough for some commercial entities to rely on it. Also, in case of a lack of ADS-B receiver data we'd also expect a grey square, not a red one, right?

I thought it might have been Square Kilometer Array interference but that's to the north of those spots.

If green or "no data" areas randomly turn red sometimes, I'd expect to see them elsewhere in the world sometimes on different days as well. But I've checked every day that's available and I never see them appear in e.g. that big empty space in eastern Russia.

I don't really see any other evidence that low data areas can turn into red areas when there's no actual interference.

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