| Popis: |
A total pointing error correction model was built to correct the pointing errors of a level mounting theodolite.Based on the opto-mechanical structure of the level mounting theodolite,a geodetic coordinate system and a pointing coordinate system were built.Then,according to the location relationship between the two coordinate systems,the target coordinate in the geodetic coordinate system was expressed.After a total differential for the target coordinate,an equation was obtained to describe the relation between target coordinate error and longitude latitude errors of the level mounting theodolite.By considering the three shafting errors to be the major ones of the system,5 linear coordinate transformations were performed to deduce a total coordinate error equation for three shafting errors.Combined with the total differential equation,a unitive compensation model of pointing error on the three shafting errors was obtained. By linear superposition with the pointing error caused by encoder errors,the total pointing error of the level mounting theodolite was gained.Finally,46 stars scattered in sky space uniformly were selected to be measured,and the discrete values of the 46 stars' pointing errors were gained in longitude and latitude dimensions,respectively.After least square fitting,the undetermined coefficients in the total pointing error model were obtained.Experimental results indicate that the total pointing accuracy can rise from 40.1″ to 3.4″ after correction,which meets the accuracy request in a general design. |
