Zero-baseline Analysis of GPS/BeiDou/Galileo Between-Receiver Differential Code Biases (BR-DCBs): Time-wise Retrieval and Preliminary Characterization

Abstract

When sensing the Earth’s ionosphere using multiple Global Navigation Satellite Systems (GNSSs) special care needs to be taken of the receiver Differential Code Bias (DCB) contributions to the error budget. For this reason timely and accurate retrieval of multi-GNSS receiver DCBs with the goal of gaining insight into their characteristics would be of relevance. In this contribution we propose a method able to time-wisely retrieve the Between-Receiver DCBs (BR-DCBs) from code measurements collected by a zero-baseline setup, thereby eliminating most common error sources. We base our investigations on dual-frequency GPS (L1+L2), BeiDou (B1+B2) and Galileo (E1+E5a) measurements collected in 2013 with a 30 second sampling rate by four geodetic grade receivers (two Trimble NETR9s, one Septentrio POLARX4 and one Javad TRE-G3TH) connected to one common antenna. For each receiver-pair, we process the GPS/GEO/IGSO/MEO/Galileo measurements separately and then obtain the time-wise estimates of five groups of BR-DCBs. With the use of statistical hypothesis testing schemes, we confirm that: (1). the time-wise estimates of BR-DCBs for all tested receiver-pairs exhibit good intraday stability; and (2). the daily weighted average (DWA) estimates of GEO/IGSO/MEO BR-DCBs are inconsistent for receiver-pairs of mixed type, due to the presence of BeiDou code Inter-Satellite-Type-Biases (ISTBs). We also identify likely factors accounting for the variability in the DWA estimates of BR-DCBs over a 1-year interval as: (1). receiver firmware upgrades; and (2). daily maximum temperature variations at receiver sites.