Combined non-contact coordinate measurement system and calibration method

• The non-contact system is proposed for measuring coordinates of the hidden zones.
• The system based on non-diffracting beam attitude angle sensor and rangefinder.
• The laser rangefinder and the angle encoder expand the scope of measurement.
• Combined measurement system satisfied the requirements in large-scale spaces.
• The weighted least squares method is superior to the ordinary least square method.

A combined non-contact measurement system comprising attitude angle sensor, angle encoder, laser rangefinder, and total station is adopted to measure the spatial coordinate of the hidden zones in large-scale space. The laser from the total station is aimed at the optical system of the attitude angle sensor to obtain the spatial coordinate and the spatial attitude angles. Then, the angle encoder driven by a stepping motor is rotated to drive the laser rangefinder to direct at the measured point. This approach is used to obtain the distance from the rangefinder to the measured point and the angle of the angle encoder. Finally, the spatial coordinates of the measured point can be calculated by using these measured parameters. For the measurement system, we propose a weighted least squares (WLS) calibration method, in which weights are determined for the angular distribution density. Experimental results show that the measurement system could expand the scale and achieve reliable precision during combined measurement and the measurement error of the weighted least squares method is less than that of the ordinary least square (OLS) method.