Description: The fundamental issue with various altimetry satellite tidal analysis is the unusual temporal resolution, as the satellites' repeating cycles span from a few to tens of days. The accuracy of tidal estimations over the Indonesian sea using multi-source altimetry data was studied in this research. The evaluation was carried out by studying and comparing the internal and external accuracy of each altimetry satellite mission based on the tide analysis results, allowing the best satellite combination to be selected. Tidal analysis was performed utilizing response methods over the Indonesian sea on 12 major tidal harmonic constants, including diurnal (K〈sub〉1〈/sub〉, O〈sub〉1〈/sub〉, P〈sub〉1〈/sub〉, Q〈sub〉1〈/sub〉), semi-diurnal (M〈sub〉2〈/sub〉, S〈sub〉2〈/sub〉, K〈sub〉2〈/sub〉, N〈sub〉2〈/sub〉), and long period (S〈sub〉A〈/sub〉, S〈sub〉SA〈/sub〉, M〈sub〉M〈/sub〉, M〈sub〉F〈/sub〉).ERM (Exact Repeat Mission) TOPEX/Jason series altimetry satellites (i.e. TOPEX, Jason-1, Jason-2, Jason-3, and SENTINEL-6A) covering the period (1993-2022), SENTINEL-3A (2016-2021), SENTINEL-3B (2018-2022), ENVISAT (2002-2010), GFO (2000-2008), and ERS-2 (1995-2011), were used in this research. These satellites' along-track altimetry was utilized for tidal analysis and modeling. The findings of this study indicate that the incorporation of ENVISAT, SENTINEL-3A, and SENTINEL-3B satellites in the construction of tidal models contributes significantly to internal and external errors of 6-30 cm and 1-10 cm, respectively. Before developing the Indonesian tidal models, the key findings of this research can be used as a guideline and a consideration in selecting the best multi-source altimetry data.

Description: The Geospatial Information Agency (Badan Informasi Geospasial) has released INAGEOID2020 as a vertical reference framework in Indonesia in 2020. INAGEOID2020 has been developed using airborne gravity and terrestrial gravity data since 2008. A Residual Terrain Model (RTM) was used to resolve the topographic effects and the Remove-Compute-Restore (RCR) method was applied in the geoid computation. The accuracy of INAGEOID2020 was evaluated by using GNSS/leveling observations. Standard deviations between 5 to 28 cm were obtained at several big islands in Indonesia. To achieve 5 cm accuracy throughout Indonesia, densification of airborne gravity data is required. Additional airborne gravity surveys were performed on Kalimantan Island in 2021 and 2022 with an interval sampling of 2Hz using GT-2A gravimeter. The line space was set to 10 NM for the main line and about 100 NM for the cross line. The flight lines were located between the lines of previous surveys (2009 and 2010). The gravity values resulted from the cross-over evaluation between the main lines and the cross line in 2021 were average of 2.03 mGal and standard deviation of 1.50 mGal Measurements in 2022 showed average of 1.25 mGal and standard deviation of 0.74 mGal. The geoid was then remodeled using the new gravity dataset, and the performance of the refined geoid model was reanalyzed. The mean differences between the refined geoid model and GNSS/leveling observations were 3.11 and 5.05 cm for the West and East Kalimantan. The result of updating geoid model indicates that there is an improvement of current model.