You need to re-calibrate your tablet's compass regularly. The easiest way to do this is to rotate the tablet 2 or 3 times around each of its 3 axes or to draw figure 8s with your tablet, as illustrated below:
You can also use certain applications. E.i: GPS Status & Toolbox that contains a compass calibration tool.
Don't hesitate to contact us if you have any questions directly via the form.
Happy Boating