Two Dimensional Vector from Accelerometer

Question

I'm trying to make an Android application that uses a smartphone moved along on a flat surface (e.g. a desk) as a mouse. Since I want to emulate a mouse, I ignore the z-axis, and figure that the best way to utilize the accelerometer data would be to construct a two dimensional vector that I could then scale to the size of the screen.

I've read other answers on SO and I see that the integration method has a large error as t increases, but I'm not sure if this error is a factor considering the short duration and position change of mouse movements (How long is the average mouse movement? I'd assume less than 2 sec.).

How would I go about designing an algorithm that meets my needs? Is an integration-based algorithm sufficient?

Answer 1

• Yes, an accelerometer data have high mistake, that would create a large errors if we'll try to get absolute coordinates out of them. But a mouse needs no absolute coordinates. Relative ones are absolutely enough. Use your integration, not a doubt in it.

• "the integration method has a large error as t increases" - correct, but a user is really interested in the last movement only. So, it will work as a mouse, and it will be felt as a normal mouse. How good the mouse will be, is up to the concrete device and the task. I am not at all sure about serious gaming, for example. You will have to do your own survey about it. But it will do really a very bad tablet/pen simulator.

• Be careful about ignoring the Z axis, for notice, even for placing a point on the map GPS uses all three coordinates - for better precision. Often movements will not have Z change equal to 0. And simply ignoring one of the coordinates, instead of recounting all three of them into two you really need, will cause greater mistakes. I am not sure you can allow it. And you simply needn't - it is NOT a heavy algorithm, devouring much time and battery. And for a user the possibility to move the device in the air could bring much convenience - not everybody wants to scratch his device against a table. So, COUNT two coordinates from three source ones, but not simply GET two of the source ones, ignoring the third.

• The problem will be elsewhere. When you use mouse and an error collected, you can raise the mouse up and move it to another point and start from it anew. You should realize something similar, too, for your device will collect errors in time as well.