Measuring velocity via iPhone SDK

Question

I need to implement a native iPhone app to measure the velocity of the phone (basically a speedometer). I know that you can do so via the CoreLocation API fairly easily, bu

Answer 1

While I don't know the iPhone API, I do know something about GPS and inertial navigation. It might be useful.

The GPS receivers I have worked with can all provide a direct measurement of velocity from the GPS signals they receive. These measurements are more accurate than position data even. I don't know if the Apple API provides access, or even if apple has configured their receiver to provide this data. This would be the more efficient route to getting a velocity measurement.

The next path, given that you have accelerometer data and GPS data is to combine them as mentioned earlier by other posters and comments. Using the GPS to periodically correct the accumulated intertial measurement from the accelerometer data works very well in practice. It provides the benefit of more frequent accelerometer measurements, and the accuracy of the GPS measurements. A Kalman filter is commonly used. But given the accuracy and timing limits of your chosen platform a kalman filter may be overkill and something simpler to implement and run should work fine.

Anyway, just some things to think about.