## 2 Experimental Setup  
A series of short baseline experiments, utilizing a u-blox ZED-F9P receiver connected to different quality and type antennas (rover) together with the IGS station DLF1 (base station, IGb14 XYZ[m] coordinates at epoch 001/2010: 3924697.776, 301125.106, 5001905.251), was conducted at the rooftop of the Netherlands Metrology Institute (NMi) in Delft. The rover antennas were installed consecutively on the pillar DOMES 13502M003 (GPS Mark 15), which is 10.404 m East, 6.928 m North, and 1.468 m Down (with a standard deviation of 1-2 mm) from the base station antenna. The installation situation is characterized by an almost unobstructed view over the full horizon and, compared to a real-life environment, the ground multipath caused by reflections of other objects and near-field effects (scattering caused by surfaces in the near field, e.g., the pillar) can be regarded as relatively clean. Nevertheless, these effects will be included in the estimated residuals. With a baseline length of approximately 10 m, delays caused by the troposphere and ionosphere can be regarded as equal for base and rover. These effects are considered as canceled in the differential processing.  
The base station consists of a Trimble NetR9 receiver connected to a Leica AR25.R3 (LEIAR) antenna with LEIT radome. The investigated rover antennas are the low-price antenna u-blox ANN-MB-00 (ANN-MB), the medium-priced antennas Trimble AV28 (AV28) and Trimble GA530 (GA530), and the geodetic-quality antennas Trimble TRM55971.00 NONE, also known as Zephyr 2 Geodetic (TRM5), and Leica AR25.R3 LEIT (same model as base station antenna). Because of the ANN-MB (antenna without screw mount) and Trimble AV28 (screw-in hole mount) antenna designs, antenna mounting adaptors were constructed. One is a metallic, rectangular bracket, and the second one is a plastic bracket with a metallic circular disk of 10 cm diameter on top. Since these are two different recording sessions using two different mounting brackets, two different datasets exist for the AV28 and ANN-MB antennas. The information is summarized in Table 1.  
The antennas cover a price range from low (<100 Euros) to high cost (>1000 Euros). All rover antennas are connected to a u-blox ZED-F9P receiver. Official IGS ANTEX type mean antenna calibrations exist for the highest-quality rover antennas (LEIAR and TRM5) as references. The LEIAR antenna calibration is used in the calibration step (see Section 3).  
The rover and base logging interval is set to 1 Hz. Using a lower frequency, with a 10- or 30-s sample rate, is possible, but will decrease the precision of the estimated PCVs slightly. Base station data are obtained from the Dutch Permanent GNSS Array (DPGA) in 15-min high-rate (1 Hz) RINEX (Receiver Independent Exchange Format) files. These are merged to daily 1 Hz data observation files. Rover data are logged on a local SD card and converted to daily RINEX files for post-processing. Since not all antennas use the same antenna adaptor, the heights from the GPS mark to the antenna ARPs are measured manually. With the exception of the circular adaptor (used by AV28 and ANN-MB), which is off by 10 mm North and 8 mm East, only height offsets are introduced by the antenna adaptor. Though measured with care, the manual measurements have a precision error of approximately 1 mm.