Most Accurate Method

Every day, at a certain time the Qibla can be determined from the sun, either by facing it or by facing the shadow from it, or else there is a time when Qibla would be 90 degress left or right of the sun. This time can be calculated for everyday for any desired location. This is the most accurate method. Remember, the compass, cannot tell you the True North, because its needle points to Magnetic North, and there is no way to know exactly how many degrees it is away from Ture North. Estimated values of the difference between True North and Magnetic North can be used but they can have errors, because magnetic field is not only changing continuously, but also can be erratic due to other physical changes present inside the earth. Moreover, the presence of other magnetic fields or metallic objects can deflect compass needle pointing in the wrong direction.