# Estimation of Inter-System Biases between BDS-3/GPS/Galileo and Its Application in RTK Positioning
## 3 Datasets and Experiments
### Datasets  
The datasets used in this article were obtained from four different stations from the International GNSS Service (IGS). To describe the information of the stations, Table 2 shows the location, position, and other information of the receivers. Station GODN is in the middle between GODS and GODE, which consists of one baseline, GODN-GODS, with the identical-receiver type of 65.16 m, and one baseline, GODN-GODE, with a different-receiver type of 76.02 m. Station USN7 forms a baseline of medium length of about 22.82 km with GODE. All the data were collected at a sampling interval of 30 s.  
In addition to the information about the stations, the visibility of satellites is equally important. The top of Figure 1 displays the sky plots of BDS-3, GPS, and Galileo. Due to the location restrictions, none of the IGSO or GEO satellites of BDS-3 can be tracked. The observed satellites include 24 BDS-3, 31 GPS, and 24 Galileo satellites. In addition, only 16 GPS satellites can transmit signals in the L5 band. The middle of Figure 1 depicts the time-series of the visible satellites of different GNSSs with a cutoff elevation angle of 10\({}^{\circ}\). The legend shows that the average number of visible satellites in BDS-3, GPS, and Galileo is 7.61, 8.71, and 6.57, respectively. The average number of visible satellites with a high cutoff elevation angle of 40\({}^{\circ}\) is 3.58, 3.90, and 3.23 satellites for BDS-3, GPS, and Galileo, respectively. To evaluate the configuration of the constellation, the position dilution of precision (PDOP) of different GNSS was introduced. The PDOP reflects not only the number of satellites, but also the performance of the distribution of the constellation. Generally, a \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Frequency (MHz)** & **Wavelength (cm)** & **BDS-3** & **GPS** & **Galileo** \\ \hline
1575.42 & 19.03 & B1C & L1 & E1 \\
1561.098 & 19.20 & B1I & - & - \\
1278.75 & 23.44 & - & - & E6 \\
1268.52 & 23.63 & B3I & - & - \\
1227.60 & 24.42 & - & L2 & - \\
1207.14 & 24.83 & B2b & - & E5b \\
1191.795 & 25.15 & - & - & E5 \\
1176.45 & 25.48 & B2a & L5 & E5a \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Frequency and wavelength of BDS-3/GPS/Galileo. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Station** & **Location** & **Receiver** & **Antenna** & **Longitude** & **Latitude** \\ \hline GODN 1  \\ GODS 1  \\ GODS 2  \\ GODS 2 [FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021. 2[FOOTNOTE:2]Footnote 2: The duration of the station GODN and GODS is from day-of-year (DOY) 29, 2020 to DOY 150, 2021. 2 The duration of the station GODE and USN7 is from DOY 36, 2021 to DOY 150, 2021.