## 2 Signal Analysis
Using the strong baseline-known model [28], the DD ambiguities \(N_{j}^{\text{ls}}\) are resolved with the search-and-shrink least-squares ambiguity decorrelation adjustment (LAMBDA) method using the integer least-squares (ILS) estimator [29; 30; 31]. The ambiguities are only considered as successfully resolved when the ratio \(\mu=R_{2}/R_{1}\) is higher than 3 [32; 33]. The \(R_{1}\) and \(R_{2}\) represent here the squared norm of the ambiguity residuals measured in the metric of the variance-covariance matrix of the float ambiguities for the best and the second best integer ambiguity candidates, respectively. The resolved ambiguities are assumed fixed until cycle slips or large data gaps are detected, and the unresolved ambiguities are treated as pseudo-observations and constrained as constant in time. To resolve possible large ambiguity sets under different elevation angles and C/N\({}_{0}\), so that possibly many phase residuals (Equation (7)) can be utilised in the data analysis, a sequential exclusion algorithm is developed and applied to exclude suspected observations that may hamper the ambiguity resolution. The detailed procedure is described in Appendix A. With the baseline coordinates and the ambiguities corrected in Equations (7) and (8), the DD residuals should contain the noise, the multipath, and the DD atmospheric residuals. The data analysis is performed using GPS dual-frequency data with 1 Hz sampling rate collected on L1C and L2W channels. To simulate different measurement scenarios, the continuously operating reference station (CORS) UWA0 located at the University of Western Australia is used as the reference station, and the station CUT0 located on the roof of a building in the Curtin University (left panel of Figure 1), which is about 8 km away from UWA0, is used as the rover station to simulate the open-sky scenario. With similar baseline length, another rover receiver mounted on the roof of a lower building, which is surrounded by trees and metal structures (middle and right panels of Figure 1), is used to simulate the suburban scenario. The station is denoted as SUB0. The receiver and antenna types of both baselines are given in Table 1. The data collected from 6:34:45 to 23:59:59 in GPS time (GPST) on 15 October 2019 were analysed for both baselines. The data were collected under quiet ionosphere conditions. Based on the Australian total electron content (TEC) maps provided by the Australian Bureau of Meteorology/Space Weather Branch (IPS) [34], during the test time periods, the test region had TEC values lower than 20 TEC unit (TECU). For the troposphere, the daily rainfall amount is 0 mm [35]. In this study, the lower bound of the C/N\({}_{0}\) in the contribution is set to 12 dBHz, which is recognised as the minimal possible signal strength [36]. The satellite having the maximum mean elevation angles for the baseline is used as the reference satellite. It remains the reference satellite until its mean elevation angle is reduced to below 30 degrees. The elevation mask is set to 10 degrees in this study. It is noted that the reference station of RTK processing is assumed to be located under good measurement environment and broadcasts its data in a continuous manner.