Improve accuracy in this IOS App

[sriharsha48]

I have downloaded this project and tried to build it.

I want to know the following things:

any method or improvisations in the code, which can improve the accuracy.
In General, when is the accuracy in measurement fine. Does that completely depend upon the feature points or is there any other factor which influences them?
If you have already conducted real life experiments with measurement,then it would be really great if you can share your experiences.

Thanks in advance!