## 2 Materials and Methods
### GNSS > Sonar > Phone System Implementation
#### 2.2.1 Devices and Apps
Two files were produced from the file containing the GNSS raw data (in *.ubx format): the first file was produced via U-center (in *.csv format) and contained mainly the coordinates of latitude and longitude, ellipsoid height and GPS Time of the positioning performed by the device in SPP in real time; the second file was produced with RTKLIB: demo5_b34f.1 (version of RTKLIB [32] developed by rklibexplorer [33] for working with the ZED-F9P and downloadable from [[https://github.com/rtklibexplorer/RTKLIB/releases/tag/b34f](https://github.com/rtklibexplorer/RTKLIB/releases/tag/b34f)]([https://github.com/rtklibexplorer/RTKLIB/releases/tag/b34f](https://github.com/rtklibexplorer/RTKLIB/releases/tag/b34f)) (accessed on 8 January 2023)) and consisted of a RINEX (Receiver INdependent EXchange) file of the observables for subsequent post-processing. The post-processed file mainly contained latitude, longitude, ellipsoidal height and GPS Time. Table 2 shows the technical features of the SimpleRTK2B. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Device** & **Deeper Smart Sonar Pro+ 2** & **Deeper Smart Sonar CHIRP+** \\ \hline Image & & \\ Beam cone & 47\({}^{\circ}\)-20\({}^{\circ}\)-7\({}^{\circ}\) & 47\({}^{\circ}\)-20\({}^{\circ}\)-7\({}^{\circ}\) \\ Frequency & 100-240-675 kHz & 100-240-675 kHz \\ GNSS & GPS, GLONASS, Galileo, & GPS, GLONASS, Galileo, \\ BeiDou, QZSS & BeiDou, QZSS & BeiDou, QZSS \\ Wi-Fi connection range & 100 m & 100 m \\ Sonar scan rate & 15x/s & 15x/s \\ Depth range min/max & 0.15–100 m & 0.15–100 m \\ Weight & 90 g & 90 g \\ Dimensions & \(\mathcal{O}\) 65 mm & \(\mathcal{O}\) 65 mm \\ Operating temperature & \(-\)20 \({}^{\circ}\)C/40 \({}^{\circ}\)C & \(-\)20 \({}^{\circ}\)C/40 \({}^{\circ}\)C \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Technical features of the Deeper Smart Sonar Pro+ 2 and the Deeper Smart Sonar CHIRP+. \begin{table}
\begin{tabular}{c c} \hline \hline
**Device** & **SimpleRTK2B** \\ \hline Image & \\ GNSS Module & ZED-F9P \\ Constellation & GPS, GLONASS, Galileo, Beidou \\ Frequency & L1C/A L2C, L1 OF L2 OF, E1-B/C E5b, B1I B2I \\ Bluetooth connection module & AS-XBEE-BT-2.4-INT-00 \\ Antenna & Lightweight helical for multiband GNSS (IP67) \\ Weight & 20 g \\ Dimensions & 69 \(\times\) 53 mm \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Technical features of the SimpleRTK2B. In this case study, a Huawei P30 Pro smartphone was used to synchronise the Deeper Smart Sonars and the SimpleRTK2B. For the implementation of the G > S > P Sys, the model of the smartphone is not particularly relevant. However, it is important that the smartphone has a good chipset and good RAM (Random Access Memory) to manage several apps at the same time in the background, an Android OS, the possibility of activating the \"mock location\" and finally the possibility of receiving data via USB OTG connection. The Huawei P30 Pro matches these features, it has a Huawei HiSilicon Kirin 980 chipset, 8 GB of RAM, the EMUI 12.0 OS, USB OTG connection and \"mock location\". The apps constituting the software part were: GPS Connector v1.0.1.7 (PilaBlu -Apps, Stuttgart, Germany), SW Maps GIS & Data Collector v2.9.1.1 (Softwet Pvt. Ltd., Kathmandu, Nepal) and Fish Deeper--Fishing App v1.22.0.3259 (Deeper UAB, Vilnius, Lithuania). GPS Connector (developed by PilaBlu) allows an external GNSS receiver to be connected to the smartphone via Bluetooth or a USB connection. GPS Connector provides the external GNSS position data to other apps that use navigation data on the smartphone via the \"mock location\" and consequently improves the GNSS positioning performance of the other apps on the device. The app was used to improve the real-time SPP positioning of the Fish Deeper--Fishing App and consequently the sonar. For this app Android 4.1 or later is required. SW Maps (developed by Softwel) has many functions related to the world of GIS (Geographic Information System) and allows an external GNSS receiver to be connected to the smartphone via Bluetooth or USB.