5:15 PM - 7:15 PM
[SCG55-P29] Searching for optimal parameter settings in kinematic GNSS analysis for GNSS-A geodesy.
Keywords:GNSS-A, Seafloor crustal deformation, RTKLIB
In the GNSS-Acoustic (GNSS-A) seafloor geodesy, where positioning of seafloor benchmark is performed by acoustic ranging between an onboard transducer and the seafloor transponders, errors in the kinematic GNSS analysis that determines the position of the onboard transducer are a major cause of the errors in the benchmark positioning. For kinematic GNSS analysis in this study, RTKLIB (Takasu 2009) and RTKLIB Explorer (Tim Everett; https://rtkexplorer.com/) which is a modified version of RTKLIB for low-cost GNSS receivers, we used for kinematic GNSS analysis in repeated GNSS-A campaigns conducted in Suruga Bay, Japan.
We analyzed actual data from GNSS-A measurements in Suruga Bay, where a total of 15 GNSS-A campaigns were conducted from April 2023 to January 2025, with GNSS data consisting of only GPS satellites obtained for 2-5 hours for each campaign at 5 Hz sampling interval. Kinematic and Precise Point Positioning-Kinematic (PPP-Kinematic) analyses were conducted to the GNSS data. For the Kinematic analysis, the baseline length to the on-land reference site was approximately 30 km. The antennas used were an HX-CSX601A (Harxon) on the observation vessel and a choke ring (Trimble) on the on-land reference station, while the receivers used were a Net-R8 (Trimble) on the observation vessel and a 5700 (Trimble) on the reference station. The results of the analysis were evaluated by comparing the one-minute average of the antenna's ellipsoidal height with the theoretical sea level from the astronomical tide, as the actual 3D coordinates of the antenna were unknown.
The analysis was carried out by changing the parameter settings in the two software. The option setting which results in the best agreement between the theoretical sea level and the antenna altitude were realized with the RTKLIB Explorer with specific parameter settings; receiver dynamics turned “ON” from the default “OFF” and ionospheric delay correction changed from the previously used “Iono-Free LC” to “Estimate TEC”. In this case, the actual altitude follows the theoretical sea level variation well, with a maximum variation of about 40 cm during a total of 15 observations of about 60 hours.
The results of the seafloor benchmark positions at the Suruga Bay from April 2023 to January 2025 which was estimated with the best GNSS solutions will also be shown in the presentation (additional observations will also be carried out in February and March 2025).
We analyzed actual data from GNSS-A measurements in Suruga Bay, where a total of 15 GNSS-A campaigns were conducted from April 2023 to January 2025, with GNSS data consisting of only GPS satellites obtained for 2-5 hours for each campaign at 5 Hz sampling interval. Kinematic and Precise Point Positioning-Kinematic (PPP-Kinematic) analyses were conducted to the GNSS data. For the Kinematic analysis, the baseline length to the on-land reference site was approximately 30 km. The antennas used were an HX-CSX601A (Harxon) on the observation vessel and a choke ring (Trimble) on the on-land reference station, while the receivers used were a Net-R8 (Trimble) on the observation vessel and a 5700 (Trimble) on the reference station. The results of the analysis were evaluated by comparing the one-minute average of the antenna's ellipsoidal height with the theoretical sea level from the astronomical tide, as the actual 3D coordinates of the antenna were unknown.
The analysis was carried out by changing the parameter settings in the two software. The option setting which results in the best agreement between the theoretical sea level and the antenna altitude were realized with the RTKLIB Explorer with specific parameter settings; receiver dynamics turned “ON” from the default “OFF” and ionospheric delay correction changed from the previously used “Iono-Free LC” to “Estimate TEC”. In this case, the actual altitude follows the theoretical sea level variation well, with a maximum variation of about 40 cm during a total of 15 observations of about 60 hours.
The results of the seafloor benchmark positions at the Suruga Bay from April 2023 to January 2025 which was estimated with the best GNSS solutions will also be shown in the presentation (additional observations will also be carried out in February and March 2025).