Iphone GPS Refresh Rate & accelerometer augmentation

Fiberoptic · 09-01-2009, 10:30 AM

According to some developer forums, the Iphone refreshes apparently every 5 seconds. From reading around, it looks like the refresh rate is so bad, we can't even use the Hz measurement.

I have been testing the iphone app motionX GPS on my Wednesday night racing and comparing it to a 1Hz Garmin marine GPS. The knot meter fluctuates by 4 knots and our VMG and bearing aren't accurate either.

The average readings are accurate, but this isn't good enough to allow us to make tactical decision on a several mile long race course.

A refresh every 5 seconds might be perfect for highway driving, but this is going to be terrible for quick sequential turns.

Maybe developers can make the GPS readouts better by artificially simulating 1-10hz gps through the use of accelerometer data.

meagain · 09-07-2009, 10:32 PM

Fiber - which iPhone has this refresh rate? All? Doesn't the 3GS handle this better? I would think it should?

Fiberoptic · 09-08-2009, 04:54 PM

Quote: Originally Posted by meagain

Fiber - which iPhone has this refresh rate? All? Doesn't the 3GS handle this better? I would think it should?

I don't have a scientific way to test the refresh rate, but the rate is very poor in comparison to an inespensive 1hz marine gps receiver. My guess is that there is some power save mode that is being used which lowers the refresh rate. Maybe some other iphone developers know how this works.

Bugbyte · 09-08-2009, 11:00 PM

I've noticed the same thing. On average it works fine, but from update to update you get a pretty wide fluctuation. That, plus GPS MotionX did something to make the reception way worse than normal!

I've used the app "Speedometer" and put it on the dash in the car to compare with the regular speedo. Again, lots of fluctuations and generally on average it is accurate.

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