First, the compass refers to the north and south poles of the earth, not the geographical north and south poles. Geographical north and south poles are due south, while geomagnetic north and south poles are not due south, but south. There is a magnetic declination between the geographical north and south poles and the geomagnetic north and south poles, and the angle is 1 1.5. That is to say, according to the geographical north and south poles, the north-south direction indicated by the compass is inherently "incorrect" and deviates from the geographical north and south poles themselves. According to the north-south direction indicated by the compass, there is of course a deviation from the east-west direction.

Second, relative to the orbital plane of the earth, the equatorial plane formed by the earth's rotation axis is also biased and "incorrect", which is more "serious" than the geomagnetic pole and geographical pole, reaching 23.5. This is also the reason why the earth will have different seasons at different positions in the orbit of revolution, and it is also the reason why the rising direction of the sun and the altitude angle at noon are different in different seasons. In the mid-latitude region (most of China is in the mid-latitude region), the sun rises from the southeast in winter and from the due east at the vernal equinox and autumnal equinox. In summer, the rising direction of the sun will turn to the northeast again. Moreover, these directions are all geographical directions and have nothing to do with the geomagnetic direction. Using a compass to determine the direction in which the sun rises every day must be biased.