Technique to measure distance from android app (between 0-60 mts)

Question

I want to measure distance travelled in a moving car from an android app. The distance is typically between (0-60 metres). How can I calculate the distance using sensors on an android device.
Thanks.

Answer 1

Your best bet is GPS. Get the location of the start and finish and use Location.distanceTo.

If you mean you want to try and calculate when you start and stop as well- I'd look for a siginificant acceleration event and correlate with GPS position at those times.

If you mean you want to not use GPS at all- give up now. The sensors are far too noisy to try and solve using acceleration equations.

Answer 2

You could (try) to integrate accelerometer values, but as Gabe Sechan said, it'll be mostly hopeless. If you spend some time analyzing your accelerometer and calibrating it manually (by this I mean compensating by your measured bias and scaling errors) you can reduce the error, but you're still stuck with a (significant) growing error that gets worse quicker over time.

As a side note, if you're constantly turning (say, in a spiral ramp), you can get the velocity directly from a combination of gyroscope and accelerometer (basically combining equations of centripetal motion "a = v^2 / r" and angular velocity "v = w * r" to get "v^2 = a^2 / w^2"). I've tried doing this with an Android device, and as long as the angular velocity "w" is high enough, the values returned are very consistent and fairly accurate (and the error doesn't grow exponentially with time as when integrating acceleration data twice).