Compass interference

Question

Level 1

45 points

Compass interference

I tried using the google maps app in the car and clicked the compass in the bottom right so it always showed me facing forward and no matter where I hold this in either of my cars the compass goes all nutty. It never shows me facing in the right direction and changes all the time. As soon as I get out of the car it's fine.

Any idea what is interfering inside the car?? This is going to be DEATH for GPS apps if this is a universal problem.

Macbook Pro 15" 2.4GHz, Mac OS X (10.5.5)

Posted on Jun 25, 2009 11:04 AM

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Answer 1

LenH

Level 2

395 points

Jun 25, 2009 11:25 AM in response to Kevin Berube

The compass doesn't use the GPS to operate and maps doesn't need the compass to navigate. So GPS will work fine with Google Maps while in the car if the iPhone has a clear view of the sky.

As for the interference, speaker magnets, the engine coils, alternator, etc....

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Answer 2

Jun 25, 2009 1:05 PM in response to Ray Golob

Ya I would think anything magnetic would be the biggest issue since thats what compasses use to determine where north is. I can usually get a minute or so of accurate use out of mine before having to redo the figure 8 motion it suggests. I probably look like a huge tard in my car swinging my phone around

The figure 8 movement is not for use in a car. Instead, drive in a figure 8 pattern (watching out for other cars, of course), or just wait until you have made enough turns.
<http://support.apple.com/kb/TS2767>

(During a figure 8 movement, don't keep the phone in the same orientation. It should be turned to follow the direction of movement.)

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Answer 3

Ray Golob

Level 1

105 points

Jun 25, 2009 11:31 AM in response to LenH

Ya I would think anything magnetic would be the biggest issue since thats what compasses use to determine where north is. I can usually get a minute or so of accurate use out of mine before having to redo the figure 8 motion it suggests. I probably look like a huge tard in my car swinging my phone around 🙂

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Answer 4

Kevin Berube Author

Level 1

45 points

Jun 25, 2009 11:31 AM in response to LenH

The GPS may not use the compass to navigate but Google Maps uses the compass to more accurately assess your position. You don't NEED a compass to navigate by GPS but it definitely affects the level of accuracy.

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Answer 5

LenH

Level 2

395 points

Jun 25, 2009 11:56 AM in response to Kevin Berube

I kinda doubt that.

The phone uses cell tower data to approximate location within a ring of certainty, then the GPS is able to get a fix on the location more exactly and more quickly. This is how A-GPS works. http://en.wikipedia.org/wiki/GPS_Phone

The compass just tells you what direction your facing, which has no bearing on your longitude and latitude.

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Answer 6

LenH

Level 2

395 points

Jun 25, 2009 11:56 AM in response to Ray Golob

THAT is funny. 🙂

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