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fjxmlzn / FindMyHistory

Track your Apple devices and look up their past location, battery levels, and more
MIT License
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Does anyone know how to interpret location|horizontalAccuracy? #10

Open andysc opened 1 year ago

andysc commented 1 year ago

In the log files, there's a field location|horizontalAccuracy which one might infer the meaning of, but doesn't have units, doesn't seem to be a percentage, so I'm wondering if anyone has any insight into how to interpret it?

I've seen values between 15 and 410 in some recent data logs, but mostly it hovers around 50-ish.

We're trying to locate a lost AirTag in a complex postal sorting machine, and any clues to get us a more accurate fix would be very helpful!

emilyboda commented 1 year ago

I would also love to know the units on horizontal accuracy. I have to assume they're in meters. Basically if the accuracy number is 30 and the unit is meters, it's saying the object is within a 30 meter radius circle of the given location. It's used so that the reader knows if the GPS fix wasn't very strong or an inaccurate method of finding the location was used.

I have two reference points: for an AirTag the horizontal accuracy values are between 15-30 most of the time. There's a handful of data points over 30, some as high as 100.

Compare that with an iPhone, for which the values vary based on the method by which the location has been found. When the location is found by GPS the accuracy varies between 0-25 with just a handful of wild values up to 250. When the location is found by wifi the values are mostly between 35-45.