## 4 Dataset Description
### Sensors Summary  
Multiple sensor types were logged during the surveys and are listed below:  
* GNSS measurements that can be associated with multiple line entries in the log file: (1) **location measurements** (latitude, longitude, altitude) provided by the phone, from different providers; (2) **raw GNSS measurements**, as described in [11; 44]; (3) **navigation messages**, as provided by the Android API and decoded by the GNSS receiver (i.e., not from another network channel).
* INS measurements, composed of two type of sensors: **accelerometers**, providing linear acceleration measurements, and **gyroscopes**, providing rotational acceleration measurements. In total, we have on each mobile device three accelerometers and three  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Scenario** & **Date** & **Device** & **GNSS** & **INS** & **Magnetometer** & **Barometer** \\ \hline \multirow{6}{*}{S1} & 17.02.2023 & GP7 & ✓ & ✓ & ✓ & ✗ \\  & 03.03.2023 & ON2 & ✓ & ✓ & ✓ & ✗ \\  & 03.03.2023 & X11 & ✓ & ✓ & ✓ & ✗ \\  & 17.03.2023 & A52 & ✓ & ✓ & ✓ & ✗ \\  & 14.08.2023 & GPW & ✓ & ✓ & ✓ & ✓ \\ \hline \multirow{6}{*}{S2} & 01.08.2023 & GP7 & ✓ & ✓ & ✓ & ✓ \\  & 01.08.2023 & GPW & ✓ & ✓ & ✓ & ✓ \\  & 01.08.2023 & X11 & ✓ & ✓ & ✓ & ✓ \\  & 11.08.2023 & A52 & ✓ & ✓ & ✓ & ✓ \\  & 11.08.2023 & ON2 & ✓ & ✓ & ✓ & ✓ \\ \hline \multirow{6}{*}{S3} & \multirow{6}{*}{11.08.2023} & GP7 & ✓ & ✓ & ✓ & ✓ \\  & & ON2 & ✓ & ✓ & ✓ & ✓ \\  & 11.08.2023 & X11 & ✓ & ✓ & ✓ & ✓ \\  & & A52 & ✓ & ✓ & ✓ & ✓ \\  & & GPW & ✓ & ✗ & ✗ & ✗ \\ \hline \multirow{6}{*}{S4} & \multirow{6}{*}{11.08.2023} & GP7 & ✓ & ✓ & ✓ & ✓ \\  & & ON2 & ✓ & ✓ & ✓ & ✓ \\ \cline{1-1}  & & ON2 & ✓ & ✓ & ✓ & ✓ \\ \cline{1-1}  & & A52 & ✓ & ✓ & ✓ & ✓ \\ \cline{1-1}  & & GPW & ✓ & ✓ & ✓ & ✓ \\ \hline \hline \end{tabular}
\end{table}
Table 3: Summary of the surveys performed and sensors logged.  
gyroscopes, placed on the three orthogonal axes (X, Y, Z), allowing re-composition of a relative motion in three dimensions.  
Additionally, an INS often include **magnetometers**, which measures the magnetic field (similar to a magnetic compass). The magnetometer enables the absolute orientation and estimation of the INS drifts [45]. Similarly to the INS measurements, three magnetometers allow the measurement of the magnetic field in three dimensions. All this information can be put together to form a low-grade INS system to be combined with GNSS measurements [1; 2; 45]. In the Android documentation, these sensors are regrouped under the term \"motion sensors\".
* Barometer measurements, related to the **atmospheric pressure** can be converted into altitude. As GNSS is known to have low precision in the up/vertical direction due to the geometry of a GNSS system, a fusion of GNSS/Barometer measurements is often seen in positioning applications [46].  
All sensor entries are located in the same file, the first column containing the tag identifying the measurement type. The entry order follows the timeline of the sensor event reception. As different sensors provide different data, a header at the beginning of the files recalls the CSV columns for each sensor type. Motion sensors can also be retrieved \"uncalibrated\", with their biases provided but not applied. In total, there are 10 different possible tags in the file. Table 11 in Appendix A provides a summary of each logged sensor measurement; additional details can be found directly in the Android developer documentation [43].