*4.1. Residual Analysis*

The presented residual analysis provides elevation- and azimuth-elevation phase patterns on both frequencies for each rover antenna. The analysis proves that antenna dependent residual phase patterns are present, and certain anomalies, for example, multipath signals presumably caused by the rectangular plate (AV28 and ANN-MB-00), can be exposed. The phase patterns can be modelled to provide corrections and/or a relative antenna calibration for our further investigations. The relative calibrations can be turned into absolute antenna calibrations in the international ANTEX format by averaging over 5 degree elevation and azimuth bins, and adding the relative calibration to the absolute calibration of the reference antenna. An important point of discussion is whether the full azimuth-elevation pattern should be used, or the elevation only pattern. The elevation only pattern is more robust and less sensitive to possible outliers than the azimuth-elevation pattern, it is also computationally less expensive to compute. Three days of data is enough to compute the elevation only pattern. To compute the azimuth-elevation pattern we advise to use more days, and/or rotate the antenna, to fill the gaps in the azimuth patterns. Additional satellite tracks over the horizon can also be obtained by utilizing multiple satellite constellations sharing the same center frequency (e.g., Galileo E1 and GPS L1). However, it introduces additional unknowns (i.e., estimation of an additional clock term) and, in the latitude of the executed experiment, still leaves the gap in the North. Consequently, a carefully conducted rotation of the antenna and accounting for it during the processing can be used to fill gaps in the azimuth pattern and at the same time average potential multipath effects. The result we obtained for the elevation only patterns were comparable to our limited azimuth-elevation patters, thus, for three days calibration time, we recommend to use the elevation only patterns. The procedure for azimuth-elevation patterns needs some further investigation.
