On the Role of GNSS Receivers for Antenna Patterns and Parameter Estimations

The precise processing of data derived by several global navigation satellite systems (GNSS) for global and regional networks relies on high-quality and calibrated equipment. Currently, an intensively discussed question in the IGS antenna working group is the best practice for publishing and distributing calibration values for receiver antennas for different systems and frequencies. There is the question of frequency band specific output of calibration values or system specific output, the magnitude of their differences and their impact the estimation parameters that are not yet assessed. We will address these points in our contribution.

Several studies performed and evaluated at our calibration facility demonstrate a systematic impact of the receiver and the implemented signal tracking concept. The expected magnitudes in GNSS processing lead to differences on the coordinate domain of a few millimetres on a short and well-controlled baseline for original observations or frequencies. These effects are superimposed and amplified when forming linear combinations of independent signals and frequencies, which, however, are essential for global GNSS processing tasks such as ionosphere-free linear combination in global GNSS networks.  These amplifications are critical as apparent biases in the coordinate and troposphere estimates are introduced with different magnitudes.

For this reason, we present a quality assessment for different antenna-receiver combinations and provide an in-depth analysis and comparison for the majority of available and existing systems, signals, frequencies and linear combinations. The data were recorded under well-controlled conditions and include GNSS data of more than one week for each of the analysed number of four geodetic and reference station grade antennas. The analysis of the different combinations of antenna-receiver configurations provides metrics for assessing the impact of the receivers on the multi-system GNSS processing and the determination of the geodetic estimates. Consequently, validation with theoretical and expected metrics derived through multiple linear combinations is investigated, with additional focus on coordinate and troposphere estimates. The analysis uses the concepts of relative (baseline processing) and absolute (precise point positioning, PPP) GNSS processing.