Based on the principle of 'D-value', special observing conditions are adopted to make the accidental errors of light ranging vary regularly. The observing method varys at the same time to equalize the numbers of the plus and minus symbols of the system error in the observing values. The accidental error, system error and the remaining error of the two are offset or counteracted by 'D-value' and hence the measuring accuracy is raised. The invention can be used in geodetic survey, engineering measurement, deformation measurement, cadastral survey, and it can also be widely used in astronomy, 'GPS' and mechanical installations. |