GNSS Vector Networks in a Local Conventional Reference Frame

The paper presents a proposal for a simple method of transforming initial GNSS vectors into a spatial local conventional reference frame. This transformation can serve as an alternative to the complex traditional procedure, which involves projecting coordinates onto a reference ellipsoid, mapping them onto a plane of an official local reference frame, and converting ellipsoidal heights into a system of orthometric heights. Local vectors (increments in horizontal coordinates and height differences) are often used in land surveying to analyse relative ground displacement, for example. The article offers a detailed definition of a local conventional reference frame and discusses its potential value for surveying practice. The proposed computation procedure was verified using a control network established to monitor displacement in a mining area. The calculated values of vector components in the local conventional reference frame were compared with the results of the traditional method for transforming GNSS vectors into official local reference frames (the PL-2000 coordinate system and the PL-EVRF2007-NH vertical reference frame). The results of both methods were verified against reference values from typical terrestrial surveys (electronic distance measurement and high-precision geometric levelling). The analysis demonstrates that the proposed numerical procedure is appropriate for control networks with certain areal limitations (up to about 300 m).