GPS Alignment Surveys and Meridian Convergence

Abstract

Since the advent of the Global Positioning System (GPS), geodetic azimuths can be accurately computed by simple implementation of well-known 3D concepts. However, when GPS alignment surveys involving azimuths are designed in advance, and later observed and reduced (e.g., during kinematic GPS work), corrections due to the convergence of the meridians should be kept in mind and not ignored. In this study a practical algorithm was used to compare accurately determined “meridian convergence” against the classical formalism available in standard textbooks. The typical approximate formulation available in the open literature was found adequate for GPS engineering surveys such as airport runway profiles, alignment of power lines or conveyor belts, stake positioning in highway construction, etc. A practical GPS survey was used to corroborate the results. Finally, a new 3D alternative to computing meridian convergence, which is equivalent to the rigorous formalism, is presented.