How to find deceleration in android using either GPS data or accelerometer?

Question

I am working on android app where I need to find hard breaks with threshold -3 meter/sec2. Can it be done using speed variation or accelerometer?

Answer 1

Speed variation would work if you would move for a long time at the same speed, so that the phone can recognize that you do so. And then the phone should be able to know when you start slowing down, and when you stop. And I don't think that it is accurate enough with GPS to do so.

The accelerometer would work, but it depends on how accurate that one is. I know that the iPhone would be enough accurate, but I doubt that a lot of Android phones can do this too.

Answer 2

I think you should use gps data, find the speed and then calculate acceleration. But I am not sure how to process the data because if you calculate only with two consecutive entries it will not be enough to find the accurate acceleration.