I'm excited about the concept of augmented reality (AR) apps, and am curious what kinds of AR apps are *practical* with the state of the art iPhone 3GS and its accelerometer, GPS, and Compass sensors. I decided to do some field tests to see how accurate the GPS and Compass sensors are on the device. In this post, I'll describe my tests, show you the data, and offer some conclusions…
Setup
Data
Below are screenshots of my iPhone using Maps, showing its measured location and course, along with a red arrow indicating where I was actually standing and pointing. I also took photos, which are not included here.
And here is a view of some GPS tracking data as I walked around the Concourse. As you can imagine, I wasn't actually staggering thru the park, but rather was walking very specific center and edge lines.
Observations
- An iPhone in motion *appears* to be more accurate than an iPhone in place, probably because a directional vector can be computed using all of the sensor data. On the other hand, standing perfectly still leads to readings that can "wiggle".
- GPS data appears accurate to within several meters, and can be useful in a variety of AR situations.
- Compass data accuracy is well within the "stated" (graphical) range, but for AR apps, that accuracy is too low to provide a satisfying experience. For instance, if I pointed at this large statue, where would an AR app display information about it?
- Is there any reason to believe that other iPhones have similar or better accuracy?
Conclusion
The current state of the art will allow us cutting-edge types to explore AR apps, but more technology advances will be needed to bring this mainstream.
Technical Details
According to this teardown, the GPS chip inside the iPhone 3GS is rumored to be an Infineon Hammerhead II and the Compass chip is rumored to be an Asahi Kasei – AK8973
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