ACCURACY IMPROVEMENT ON SEA SURFACE HEIGHT ESTIMATION BASED ON WAVEFORM RETRACKING ANALYSES OF JASON 2 SATELLITE IN JAVA SEA
A waveform created by the reflected signal from altimeter satellite in offshore is generally in ideal shape (Brown waveform) and produces an accurate sea surface height (SSH) estimation. However, over coastal waters, the waveform shape becomes complex due to a disruption by reflected signal from land, resulting inaccurate SSH estimation. The objective of this research was to improve the accuracy of SSH estimation employing waveform retracking analyses of Jason 2 altimeter satellite data in the Java Sea during the years of 2012 2014. This study used data from the Sensor Geophysical Data Record type D (SGDR D) from Jason 2 satellite (cycle 129 239) and global geoid undulation data of Earth Gravitational Model 2008 (EGM08) Waveform retracking analyses were conducted using several retracker methods The performance of the all retrackers were examined using a world reference undulation geoid of EGM08. The results showed that the waveform retracking analyses were able to improve the accuracy of SSH estimation approximately 29.7% in the north coast and 56.4% in the south coast of total non Brown waveform in each region. Higher improvement percentage (IMP) of SSH estimation found in the southern coastal areas was due to a relatively smooth coastline formation in this region than in northern coastal region. There was no specific retracker that produce dominant IMP of SSH estimation. However, the threshold 10% retracker produced better SSH estimation than the other retrackers with dominant IMP values of 57.1% (pass 051) 48.1% (pass 064) and 25.7% (pass 127) OCOG retracker the worst retracker to estimate SSH in the Java Sea. Keywords: EGM08, waveform retracking, SSH, Jason 2, ocean retracker, threshold retracker