In an old map, line PQ was drawn to a magnetic bearing of 6°32', the magnetic declination at that time being 1° East. The present magnetic declination is 9°42' East. The magnetic bearing to which the line is set at present is

Based on the Gaussian law of distribution of random errors, the number of errors that are expected to exceed the limit of ± a, where 0 represents the standard deviation, out of 1000 observations is

In a trigonometric levelling, the height of the signal used is 4.62 m and the instrument height is 1.25 m. If the horizontal distance of the target from the instrument is 5780 m, then the axis-signal correction is