Ideas on iOS GPS tracking needed

[Bob Sneidar]

Seems to me if you are tracking linear movement, you need to average the trending values, say the last 5 or 10 reads, against a time base, and reject the ones outside an acceptable tolerance. You may reject some good data here and there, but something grossly outside tolerance should be pretty easy to grok.

Sounds easy, huh? :-) But it really is. For a car moving at 60mph, obviously the trend is going to be greater than a person walking, and slower than a small airplane. For an alien spacecraft traveling at insane speeds and making wild maneuvers, I’m afraid you are on your own. The tolerance can be a percentage of the average of the last x reads or the last x seconds. Seconds makes more sense to me since if you drop 2 or 3 reads it will skew the averages significantly. That is likely how Google Maps does it.

Bob S


On Nov 3, 2020, at 2:39 PM, Alan Stenhouse via use-livecode <use-livecode at lists.runrev.com<mailto:use-livecode at lists.runrev.com>> wrote:

Hi Graham

Are you checking the horizontal accuracy of each reading? (It's part of the array of data with your lat-longs, as well as speed, etc - though not on every phone).

If not, try that and see if the anomalous readings are hugely out. From my experience, that's normally the case. If so, the easiest thing is to drop them in the short term, unless you get too many and then you may need to be a bit fancier. If you do, would love to hear the solution that you come up with.

HTH, cheers

Alan