GPS code phase variations (CPV) for GNSS receiver antennas and their effect on geodetic parameters and ambiguity resolution

Abstract

Precise navigation and geodetic coordinate determination rely on accurate GNSS signal reception. Thus, the receiver antenna properties play a crucial role in the GNSS error budget. For carrier phase observations, a spherical radiation pattern represents an ideal receiver antenna behaviour. Deviations are known as phase centre corrections. Due to synergy of carrier and code phase, similar effects on the code exist named code phase variations (CPV). They are mainly attributed to electromagnetic interactions of several active and passive elements of the receiver antenna. Consequently, a calibration and estimation strategy is necessary to determine the shape and magnitudes of the CPV. Such a concept was proposed, implemented and tested at the Institut fur Erdmessung. The applied methodology and the obtained results are reported and discussed in this paper. We show that the azimuthal and elevation-dependent CPV can reach maximum magnitudes of 0.2–0.3 m for geodetic antennas and up to maximum values of 1.8 m for small navigation antennas. The obtained values are validated by dedicated tests in the observation and coordinate domain. As a result, CPV are identified to be antenna- related properties that are independent from location and time of calibration. Even for geodetic antennas when forming linear combinations the CPV effect can be amplified to values of 0.4–0.6 m. Thus, a significant fractional of the Melbourne–Wubbena linear combination. A case study highlights that incorrect ambiguity resolution can occur due to neglecting CPV corrections. The impact on the coordinates which may reach up to the dm level is illustrated.