Absolute GNSS Antenna Phase Center Calibration with a Robot

Abstract

GNSS antennas suffer from errors, dependent on the direction of the incoming GNSS signal. These errors can be calibrated. We present an absolute field calibration method based on a 6-axis industrial robot. The antenna to be calibrated is set-up on the robot at one end of a short baseline. The robot brings the antenna into 1440 different orientations without changing its coordinates, every orientation lasting for 1 second. The data is analyzed in a triple-difference approach. The estimated GPS L1 phase center corrections show a repeatability better than a millimeter (0.6 mm RMS). We belief that this new method is of interest to the scientific community, as only a few independent field calibration systems exits.