Real-time Cycle Slip Detection and Repair for Network Multi-GNSS, Multi-frequency data processing

The GNSS community is experiencing a new era with the development of the multi-GNSS and multi-frequency industry. For high-precision GNSS data processing with the use of carrier phase measurements, quality control steps, such as, cycle slip detection and repair, are essential. With the correct detection and repair of the cycle slips, the carrier phase measurements will not be lumped by the unknown integer jumps. Therefore repeated integer ambiguity resolution in RTK or long convergence time in PPP, or PPP-RTK, will be avoided, especially in the extreme case of full loss of all the signals. In this contribution, a cycle slip detection and repair procedure, which has been implemented into our real-time Analysis Centre Software (ACS) preprocessing and data editing (PDE) function, is presented. At first, the noise levels of Hatch-Melbourne-Wübbena (MW) and Extra MW (EMW) linear combinations are investigated. The cycle slip detection approaches based on linear combinations and quality control theory under statistical hypothesis testing are then comparatively studied with multi-GNSS and multi-frequency data. As soon as the cycle slips are detected, mathematical and stochastic models for cycle slip repair are established. These models rely on timedifferenced code and carrier phase measurements, as well as prior knowledge of the time-differenced ionosphere residual. The least-squares estimation is used to estimate the unknown parameters and their variancecovariance matrix. The float cycle slips and their variance covariance matrix are then used to reliably repair the cycle slips based on Integer Least-squares (ILS) estimation. Overall, the numerical results indicate the effectiveness of the implemented method for real-time network multi-GNSS and multifrequency data processing. Moreover, the benefits of the triple-frequency cycle slip detection and repair algorithm are demonstrated.