Atmosphere Decomposition for VRS-Based Network-RTK System

The atmospheric delay is the main error source for medium-range relative GPS positioning, and therefore is the main challenge for Network-RTK systems. The double-differenced tropospheric and ionospheric delays are decomposed from the double differenced ionosphere-free and geometry-free combinations. However, for a Network-RTK system, the atmospheric delays are required to be expressed as single-differenced or zero-differenced values, it is necessary to decompose the atmospheric delays from double-differenced values to single-differences. As tropospheric delays are non-dispersive, they are calculated with long duration data series, and the zero-differenced tropospheric delays can be extracted using tropospheric mapping functions. In the case of the ionospheric delays, the single-differenced ionosphere delays are calculated using a constraint condition derived from the predicted total electron content information.