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View Full Version : iPhone GPS - any way to access speed/direction?




imrtt
Jul 19, 2008, 06:02 PM
Posted this in Mac programming forums first by mistake, my bad.

Am I missing something, or is there no way to get speed/heading from CLLocation / CLLocationManager? I can't believe Apple would leave those attributes out.



ayasin
Jul 19, 2008, 11:00 PM
Given 2 position readings it's not hard to calculate. There's already a distance calculation. Given distance and time calculating speed is trivial. Calculating direction is a bit more involved and requires some trig, but even that's not that difficult.

jasonbrennan
Jul 21, 2008, 12:52 PM
And there's always the accelerometer, so long as you aren't moving at a constant velocity...

psingh01
Jul 21, 2008, 03:20 PM
I don't have an iPhone 3G, but I have a wireless 3G modem with built in GPS. From OSX I can read the gps data directly from the serial port (i.e. just a file in the /dev/... directory). Maybe this is possible with iPhone OS with it's built-in gps? If you can figure out what the device file is.

chrisesposito
Dec 9, 2008, 10:06 PM
I believe that the 2.2 update has added direction and speed to CoreLocation

cpatch
Dec 10, 2008, 12:43 PM
2.2 adds the following to CoreLocation:

CLLocation.course
CLLocation.speed
CLLocationDirection
CLLocationSpeed

Craig

firewood
Dec 10, 2008, 04:01 PM
I can read the gps data directly from the serial port

The SDK provides no access to raw NMEA data. Instead you have to use Core Location.

Prior to 2.2, you have to use some spherical trigonometry formulas and subtract coordinates to get direction, and DSP filtered numerical differentiation to get a good estimate for speed.

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