# Precise Point Positioning Using Dual-Frequency GNSS Observations on Smartphone
## 3 Experiments and Results
### Static Data Collection  
A 24-h static data set was collected using Mi 8 and Hi-target iRTK-2 geodetic receiver with a data rate of 1 Hz on the roof top of the Geological Palace Museum of the Jilin University (43.8802\({}^{\circ}\) N, 125.3021\({}^{\circ}\) E), November 12, 2018 (DOY 316 09:20:00-DOY 317 09:20:00 UTC). Figure 2a depicts the experimental equipment and environment, and we measured the distance from the bottom of the receiver to the smartphone in vertical plane and corrected it to the antenna phase center of the receiver using antenna calibrated data from manufacturer. The height between the receiver antenna phase center and phone position was 1.6939 m, the distance from the bottom of the receiver to the smartphone was 1.5997 m and the calibrated data from the bottom of the receiver to the of the antenna phase center was 0.0942 m. To avoid disturbing the other sensors, WIFI and Bluetooth were turned off, and the accelerometer, gyroscope, magnetometer and pressure were disabled during the data collection. Geo++ RINEX Logger was used to receive RINEX 3.0 data because the smartphone cannot directly record data in RINEX format [29]. To illustrate the validity of the arrangement of the receiver and smartphone shown in Figure 2a, an experiment was performed to evaluate the multipath effects of smartphone in different cases. We put the smartphone on the edge of the roof (Figure 2b), and compared the collected data with those placed under the GNSS antenna at the same time in the adjacent days. \(MP_{1}\) and \(MP_{5}\) are employed to evaluate the multipath effects, and can be expressed as:  
\[MP_{1}=P_{1}-\left(1+\frac{2}{\alpha-1}\right)\wp_{1}+\left(\frac{2}{\alpha-1} \right)\wp_{5} \tag{35}\]  
\[MP_{5}=P_{5}-\left(1+\frac{2}{\alpha-1}\right)\wp_{1}+\left(\frac{2}{\alpha-1} \right)\wp_{5} \tag{36}\]  
where \(MP_{1}\), \(MP_{5}\) are linear combinations of pseudorange and phase observations, \(P_{1}\) and \(P_{5}\) are code measurements on L1 and L5, respectively, \(\wp_{1}\) and \(\wp_{5}\) are phase measurements on L1 and L5, \(\alpha=f_{1}^{2}/f_{5}^{2}\)  
Figure 1: The cycle slip rate of 30-minute observations before and after turning on “duty cycle” (data collected by Mi 8 on October 7 th, 2018 in the basketball court, Jilin University). is a constant. Figure 3 and Table 2 show the multipath of the two cases, and there were no obvious differences between the two cases. The possibilities of the existence of additional multipath and the signal received by the smartphone being corrupted by the antenna were quite low. Figure 3: Horizontal position errors of four data sets in PPP kinematic mode. Figure 2: View of data collection at roof of Geological Palace Museum ((**a**) under the GNSS antenna; (**b**) on the edge of the roof). The PDOP (Position Dilution of Precision) and the number of satellites recording L1 and L5 frequency data simultaneously viewed by smartphone are depicted in Figure 4. In the 24-h data collected by smartphone, the periods of more than 4 satellites were 13 h. 12 of the 31 GPS satellites and 18 Galileo satellites can transmit signals in the L5 band, and the geometric distribution of Galileo satellites are poor in the Asia-Pacific region, resulting in fewer than four satellites in many epochs. Considering the availability and continuity of data, the first six hours data (09:20-15:20 UTC) were selected for static PPP processing. In six-hour period, the number of satellites exceeded 4 in most of the time, but there were about 20 min at around 12 o'clock with fewer than 4 satellites. For the PDOP, the value was more than 4 at around 10 o'clock and 15 o'clock, and the duration of the two periods was about 40 min. The number of satellites was maintained at more than 4, and the PDOP was smaller than 4 for 4.5 h approximately.