## 5 Impacts of the Microwave Absorption: Observation Results
The computation of the pseudorange multipath combinations within each GNSS constellation assumes that the biases are held constant only when there are no cycle slips while tracking the GNSS signals, so in practice, the mean component of the multipath combination is removed; as a result, only the RMS variations are reported [20]. Figure 5 shows the code multipath for the two GNSS stations KBG1 (top) with Eccosorb and KBG2 without Eccosorb (bottom) for all possible linear combinations. The RINEX 3.04 format is used to produce this analysis employing all the available frequency bands for January-May 2021. In general, the code multipath shows a steady estimate with some small minor variabilities in GPSM1X and on all BeiDou multipath linear combinations. In general, BeiDou signals performed the worst for both stations and GLONASS M1C, and M2C showed the next worst performance, followed by GPS M1C. Galileo signals showed the best performance with a particular best performance from Galileo M8X for both stations due to a wide-band alternate binary-offset-carrier (AltBOC) modulation [32]. A slight variation exists with the other multipath linear combinations within the Galileo frequency bands, with slightly M1X multipath linear combination lower performance, again depending on the modulation used. The station KBG1 with Eccosorb material shows a much better performance than the KBG2 with no Eccosorb material. The performance of Galileo stations is much better for station KBG1 with Eccosorb compared to KBG2 station. On average for Galileo, the signal performs more than 60% better for the station with Eccosorb, KBG1. For GLONASS, particularly for M3X and M1P multipath combinations, the performance improved up to 50%. For BeiDou, the improvement is more than 30%; for GPS the improvement reaches 40 %; see Figure 6 for the relative improvement. For high-precision positioning applications, detecting cycle slip is crucial. Carrier-phase measurements are susceptible to cycle slips, causing a bias in GNSS observables and, if undetected (and uncorrected), affecting the estimated station coordinates. For real-time kinematic solutions, cycle slips must first be identified and repaired to aid faster ambiguity resolution and improve positioning accuracy. Typically, a multipath causes the degradation of receiver tracking capabilities and potentially introduces cycle slips in the recorded GNSS observables. Figure 7 depicts the number of identified carrier-phase cycle-slips during a continuous phase tracking for colocated stations for the period January 2021 until the 5 th of May 2021 using the Trimble Alloy reference receiver. Figure 7a shows the cycle slips for the four GNSS constellations, i.e., BeiDou, Galileo, GLONASS and GPS, for carrier-phase  
Figure 5: Pseudorange (Code) multipath estimated for all possible linear combinations as recorded at stations KBG1 (**a**) and KBG2 (**b**) during January–May 2021. Figure 6: Improvement of pseudorange (Code) multipath estimated for all possible linear combinations as observed at station KBG1 with Eccosorb with respect to KBG2 without Eccosorb averaged over the period January–May 2021.  
observables. Clearly, the carrier-phase tracking shows very few cycle slips for the two close-by stations under investigation, with BeiDou and GLONASS performing worse. Galileo and GPS perform much better. The carrier phase cycle slips for BeiDou L1X and L5X and GLONASS L3X show very few cycle slips, as does the Galileo carrier phase signals; L1X (E1), L5X (E5a), L6X (E6), L7X (E5b) and L8X (E5a + b) and the GPS carrier phase signals; and L1X, and L2X as recorded by Trimble Alloy reference receivers. While the cycle slips for GPS carrier phase signals for L2X, L1C and L2W are relatively small, less than 50, the small number of cycle slips using Eccosorb material is appreciable. Figure 8 shows an improvement in percentage using Eccosorb material compared to the station without the Eccosorb. The Galileo carrier phases show no change.