Improved positioning method for digital zenith camera

The original positioning method for digital zenith camera has the problems that its calculation process is complicated and during the process some errors are introduced. By changing the way of time compensation and optimizing the iteration core, an improved positioning method was proposed. The mean in tangent plane is calculated by this method, so it can eliminate the errors in original method. Besides, by this method, the positioning process can also be simplified by avoiding the repeated calculation of tangent transformation and inverse tangent transformation. The efficiency and accuracy of these two methods were compared through experiments. The result shows that, the efficiency of improved method is more than 6 times higher than the original one; the declination calculated by improved method is 1.05 m more accurate than the original 15 m. Therefore, compared with the original method, the positioning accuracy is improved with the improved method.