Comments on: iPhone 3.0 Beta 5: Digital Compass Settings Found in Debug Menu

By: sulimon

sulimon — Sun, 09 Aug 2009 18:42:32 +0000

they use accelerometer in conjunction with compasses in two directions, giving you three angles: horizontal, vertical, rotational. NOW i understand how wikitude does it. that stuff isn't as hard as people think; pretty soon there will be libraries so that any developer can make augmented reality apps.

By: James

James — Mon, 27 Jul 2009 09:00:40 +0000

@icebike

Google is your friend. Use http://www.magneticsensors.com/landnav.html if you want to know how digital comps. work.

Cheers, http://www.realityinfo.org/news http://www.youtube.com/realityinfodotorg

By: edwald

edwald — Wed, 08 Jul 2009 07:55:14 +0000

One way it could be done, is to use GPS to establish the directions, whenever the device "sees" a satellite, while in motion (any GPS device can do this) and then maintain the orientation (as of last GPS "fix") with an internal electronic gyroscope. Such things exist, I don't know if Apple used any. Just guessing.

By: frank_rizzo

frank_rizzo — Mon, 06 Jul 2009 21:55:27 +0000

No, i don't think that the compass is using magnetism to detect north. A magnetic compass does not need to be re calibrated periodically by waving in a figure 8 motion, also the 3gs compass is less accurate than a typical magnetic compass. Im pretty sure they are using some other trick than magnetism to do it.

By: thekevinmonster

thekevinmonster — Fri, 08 May 2009 18:46:29 +0000

@icebike: oh, I was responding to the bit about where you said you didn't know why it would be useful.

I assumed wikipedia would explain it but the answer was vague, although apparently it's a multi-axis sensor. I guess the assumption is, if it detects a magnetic field going "this way", that way is pointing to magnetic north. I think you hold a regular needle compass flat so it can spin - if you made the sensor part a sphere, it could float in something and point towards north even if it was upside down.

You could probably also use the accelerometer to tell which way the device was oriented with respect to gravity, unless you were accelerating some other direction.

By: icebike

icebike — Fri, 08 May 2009 17:22:19 +0000

@thekevinmonster:

I understand the difference between a GPS and a Compass, as a reading of my post would have revealed.

What I don't understand is HOW a digital compass works. A magnetic compass (spinning needle) needs to be held flat. How does a Digital compass physically work.

By: thekevinmonster

thekevinmonster — Fri, 08 May 2009 13:17:51 +0000

Wow, somehow I totally butchered my comment.

By: thekevinmonster

thekevinmonster — Fri, 08 May 2009 13:17:34 +0000

Video capture, digital compass, GPS support. Can you say augmented reality?

@icebike: You need a digital compass to tell which direction the device is oriented. Accelerometers can tell which way it's moving and how fast it's accelerating (although I've heard the iPhone's is odd in that it always operates with respect to gravity so if you move it strictly in one plane left to right it doesn't know anything happened.) A GPS will tell you where the device is on Earth. But if you want to know which direction you're facing, if you've turned around in a circle, etc? You need a magnetometer.

If you combine video capture capability, GPS, accelerometer, and magnetometer, you now know where you are in space and can overlay graphics on the camera input. Tada! Augmented reality.

By: icebike

icebike — Fri, 08 May 2009 05:30:40 +0000

Google's G2 Android phones will let you jump into screet view and then swing the phone around your head to change your view direction. Face North, you are looking North in street view.

When you are moving, the GPS can calculate which way you are heading, but when standing still the compass would be useful, especially if you want to know which way to go without actually moving. Finding North on a perfect gray day can be a challenge unless you move far enough for the GPS to calculate your direction.

Still I'm hard pressed to see this as terribly useful for other than map applications.

Maybe photo tagging, so you know location and bearing on your snaps would be cool.

How does a digital compass work anyway?

By: Wesley

Wesley — Fri, 08 May 2009 05:05:30 +0000

It could be used to rotate the map from Maps to north, so it would be even easier to follow it, as it would behave like the hud map on many games like GTA, hehe.