In Apple Developer API, The horizontal location accuracy does not specify a confidence of accuracy.
https://developer.apple.com/documentation/corelocation/cllocation/1423599-horizontalaccuracy
In Android document, it says the accuracy is stated with 68% certainty. https://developer.android.com/reference/android/location/Location#getAccuracy()
Can someone clarify if Apple's accuracy is with 68% or maybe 95% confidence?
Thanks.
You probably read this already: https://stackoverflow.com/questions/30673627/location-accuracy-defined-ios/31129449#31129449
According to someone who seems to have some knowledge about it, it would be 95-98%
Excellent question! The short answer is that a circle with radius horizontalAccuracy centered on the associated latitude and longitude is expected to contain the true latitude and longitude somewhere between roughly 63% and 68% of the time.
In greater detail, the horizontalAccuracy field should be interpreted as an estimated two-dimensional root mean square error, calculated from a scaled Chi distribution with two degrees of freedom. In other words, if sigma_e and sigma_n are the one-dimensional standard deviations of location errors in the east and north directions at the associated location, then horizontalAccuracy for that location will be reported as sqrt(sigma_e^2 + sigma_n^2). Valid values of horizontalAccuracy are 0 < horizontalAccuracy <= Inf. horizontalAccuracy == 0 specifies a perfectly-known location and is unexpected. Negative values indicate the associated location is invalid.
Under ideal circumstances, a circle centered on the associated latitude and longitude with radius horizontalAccuracy contains the true latitude and longitude somewhere between roughly 63.2% and 68.3% of the time. If the actual distribution of location errors is roughly equal in each of the east and north directions at the associated location, then the circle contains the true latitude and longitude roughly 63.2% of the time. If the actual distribution of location errors is much larger in one direction than in another, then the circle contains the true latitude and longitude roughly 68.3% of the time.
Similarly, a circle centered on the associated latitude and longitude with radius 1.73 * horizontalAccuracy contains the true latitude and longitude roughly 95% of the time. A circle centered on the associated latitude and longitude with radius 2.15 * horizontalAccuracy contains the true latitude and longitude roughly 99% of the time.
The circles described above approximate the horizontal error characteristics for the corresponding location estimate under ideal circumstances. Actual error characteristics may vary considerably in practice.
