Study on automated gyrotheodolite based on unified north-finding algorithm

Gyrotheodolite is a measuring instrument to determine precise true azimuth. During the course of measurement, rough north-finding and precise north-finding are two necessary steps. The two steps used to adopt different methods to carry out, which increases the complexity and difficulty for automated north-finding and also extends the measuring time. Here, we evaluate a novel approach that unifies rough north-finding and precise north-finding in one algorithm. The cursor data of gyro motion can not be collected for enough period of oscillation in any initial azimuth of gyrotheodolite. Based on gyro characteristics of motion, the trend projection method is put forward to predict the whole period of movement data with a small or enough part of captured cursor data by using nonlinear regression. With this method, the north-finding result can be calculated in any initial azimuth for fixed collimation of gyrotheodolite. By automated design of the system, the gyrotheodolite will automatically approach true north gradually in terms of north-finding results until it reaches precise true north. This method provides a new idea for automated gyrotheodolite with a unified and quick north-finding algorithm.