TIDE OBSERVATION USING GNSS REFLECTOMETRY METHOD

• Main Author: Syetiawan, Agung
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/70754
• Institution: Institut Teknologi Bandung

In defining the vertical datum, tide observation is used to obtain height by referring to mean sea level. Hitherto, tide observation can be carried out using two methods: 1) in-situ using tide gauge; and 2) satellite-based using altimeter satellite. However, implementation of these two methods in coastal areas is still considered not optimal. This is due to the inadequate resolutions, both spatial and temporal, for complex and rapidly changing sea level observation. Currently, another alternative method is being developed to observe the sea level by utilizing the GNSS multipath signal. This method is known as GNSS Reflectometry. Unfortunately, there are still problems related to the accuracy and temporal resolution of the tides produced. Implementing quality control and adding satellite segments can improve accuracy and temporal resolution. The purpose of this research is to observe the sea level height from the reflected GNSS signal. GNSS Reflectometry technique utilizes multipath signals that have been considered as noise in precise GNSS measurements. The signal reflected by the sea is then analyzed using the Lomb- Scargle Periodogram (LSP) method. LSP calculates the vertical distance of the reflected plane surface based on the dominant frequency of the multipath signal from the peak value of the wave. Statistically, the estimated peak from one LSP shall not be considered as the accurate value. Therefore, the quality control process is used to increase the quality of the estimated reflector height. The results showed that the sensitivity of quality control greatly determines the final result of the tidal signal. Furthermore, the combination of GPS and GLONASS at the L1 and L2 frequencies produces a tide with an RMSe value of 8cm and a correlation of up to 97% when compared using tide gauge observations. Finally, the use of GNSS iii antenna installation at tidal stations provides another alternative in sea level monitoring. The GNSS-Reflectometry technique can be used as a complement to tide observations at the Geospatial Information Agency.