Compass Accuracy

Question

Level 1

7 points

Compass Accuracy

Just got my 3Gs and playing with the compass app and it doesn't always seem consistent that North is in the same place. Its always fairly close maybe only a 5 to 10 deg out. Anyone else noticed it?

Also are there any good apps that make use of the compass otherthan the built in one and maps?

Shouldn't google street view also use the compass and when you turn when viewing the street this automatically turn like it does on the G1 Android phone???

Thanks

Dell XPS 420, Windows Vista

Posted on Jun 23, 2009 1:04 PM

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Answer 1

MobileDev

Level 3

565 points

Jun 23, 2009 1:17 PM in response to mdavenport

It's not meant to be a super accurate compass. Are you near any metal or magnets? Apple says that even having your earbuds nearby can throw it off.

Did you set up whether you want Magnetic or True North using its "i" setting? For True North it'll need to know your basic location for calculating declination (aka variation).

Apps that use the compass are coming. The first ones will probably be ports from Android, which has some neat ones like the tourist guide and star almanac.

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Answer 2

Jun 26, 2009 6:44 PM in response to MobileDev

My compass is constantly looking about 20 degrees in the wrong direction on google maps. When I am looking down a street, it will be looking to the right 20 degrees off the road. It does this wherever I go. In the car, the compass on google maps looks to the right 20 degrees off the road. I try re-calibrating, but it doesn't change. Anyone know what might be causing this?

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Answer 3

Jun 27, 2009 6:44 AM in response to mdavenport

Is it set for true north? Press the "i" at the bottom-right to get to the settings.

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Answer 4

Jun 27, 2009 6:53 AM in response to akakyliente

I have had similar issues. Also when laying flat on the table and standing it up (without changing direction) it changes direction by many degrees. I am waiting for a replacement to come in today for this and a screen issue.

The first phone did not have this issue. It was pretty accurate...

If you have some time to spare you could make an appointment at the genius bar and have them look at it/ compare it to other phones...

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Answer 5

mdavenport Author

Level 1

7 points

Jun 30, 2009 10:07 AM in response to mdavenport

Mine is set for True North. I have set this to magnetic north and the compass is more eratic especially near computer objects like wireless mice and keyboards.

Is it best to have it set on True or Magnetic?

Since my original post I have tried my wifes and a colleagues at work and both give similar strange results. One minute it can be point where I thought was north and the next (only after moving centimeters to the left) does north appear about 20 deg out... odd...

Could this simply be the nature of the compass or is it a fault or just down to the amount of intaference around?

I am sure I used the compass in my car before, however the other day driving to work it was 180deg out. It said I was going north and I know for a fact I was going south and also east at different times. I switched to maps and enabled compass as it looked as it I was driving sideways down the road..

All feedback welcome as I don't believe I am alone on this one...

Thanks
Mark

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Answer 6

LenH

Level 2

395 points

Jun 30, 2009 11:16 AM in response to mdavenport

Automobiles have all kinds of sources of magnetic fields -- car radio speakers, coils on the engine and solenoids. I wouldn't expect a compass to work well in a car.

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Answer 7

kenm2474

Level 1

7 points

Jun 30, 2009 11:27 AM in response to LenH

+Automobiles have all kinds of sources of magnetic fields -- car radio speakers, coils on the engine and solenoids. I wouldn't expect a compass to work well in a car.+

Thats the whole point of haveing a GPS Compass on the iPhone. Thats like making a Soccer Ball that cant be kicked or a Basketball that cant be bounced.

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Answer 8

Jun 30, 2009 12:15 PM in response to mdavenport

Any electronic compass needs to be calibrated. Hold it out at arms length away from any magnetic or large metal objects and slowly make a series of circle 8's for about a minute. I found this on Apple's website and followed the instructions and now my compass is accurate.

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Answer 9

LenH

Level 2

395 points

Jun 30, 2009 12:34 PM in response to kenm2474

kenm2474 wrote:
Thats the whole point of haveing a GPS Compass on the iPhone.

Do you have a reference for this?

You seem to be dismissing physics.

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Answer 10

paulcb

Level 6

19,239 points

Jun 30, 2009 12:39 PM in response to kenm2474

GPS does not need the Compass to work. GPS determines direction based upon movement, not based upon the Compass. It may use the Compass to determine heading when not moving but I'm not sure. I'm not even sure if the iPhone's GPS uses the Compass as all. Anyone?

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Answer 11

LenH

Level 2

395 points

Jun 30, 2009 12:48 PM in response to paulcb

Compass shows which direction the phone is facing based on electromagnetic fields generated by the earth. If there is interference, it will not be accurate.

GPS on the iPhone uses tower location data to approximate the location of the phone and then uses satellite reception to calculate a more exact location of the phone. If the satellites are obscured (by a roof, trees or tall buildings), the GPS will not be very accurate, but the cell tower data will get you close.

Neither the GPS nor the compass rely on each other, as they have different purposes.

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Answer 12

paulcb

Level 6

19,239 points

Jun 30, 2009 12:59 PM in response to LenH

Agreed on all points. I don't have a 3GS and wasn't sure if Apple somehow integrated the compass with the GPS. Considering the problems of using a compass like this in a car, likely not.

One flaw of all GPS systems, including my Nuvi, is that your heading is usually off when stopped or traveling very slow. This is usually not an issue but when you're in a city with lots of stoplights spaced close together and lots of turn options, following the GPS can be a bit tricky because you're heading is often off. I know this from experience. Using a compass to maintain heading when stopped or moving very slowly would be a nice GPS feature.

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Answer 13

kenm2474

Level 1

7 points

Jun 30, 2009 1:00 PM in response to paulcb

Reference??? Look at your iPhone. Your reference is right there. Why would you have a double tap location button so you face in 1 direction on the MAP if that wasnt the case.

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Answer 14

LenH

Level 2

395 points

Jun 30, 2009 1:09 PM in response to kenm2474

Do you have a reference that the compass must work in a car?

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Answer 15

kayjh

Level 1

140 points

Jun 30, 2009 1:34 PM in response to MobileDev

That's for magnetic north. Magnetic variation for a specific location can be looked up. For true north, you need to look at a map and determine the direction of north from the indicator on the map.

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