Toward Instantaneous Network-Based Real-Time Kinematic GPS over 100 km Distance

Abstract

ABSTRACT: Instantaneous (single-epoch) ambiguity resolution may not always be possible because of the increasing noise and lack of sufficient redundancy to verify the integer selection in long-range real-time kinematic (RTK) GPS positioning. The algorithm proposed here is based on a single-baseline solution aided by double-difference (DD) ionospheric delay from the previous epoch (up to 60 s latency in DD ionospheric delay can be accepted), which supports the ambiguity resolution and provides a quality instantaneous kinematic position over long distances. However, obtaining the initial DD ionospheric delay requires atmospheric corrections provided by the reference network and some accumulation at the beginning of the session—i.e., on-the-fly (OTF) initialization is needed. Afterwards, instantaneous RTK positioning is assured. In this paper, a feasibility test of instantaneous real-time rover positioning is presented, and the effect of the latency of the DD ionospheric corrections on the instantaneous ambiguity resolution in long-range RTK is investigated. The positioning accuracy achieved in the tests, expressed as the differences between the resultant coordinates and the known “true” coordinates, is at millimeter-level accuracy for the horizontal components and centimeter-level for the vertical one for baselines over 100 km long.