Regional mean sea surface and mean dynamic topography models around Malaysian seas developed from 27 years of along-track multi-mission satellite altimetry data

Contemporary Universiti Teknologi Malaysia 2020 Mean Sea Surface (UTM20 MSS) and Mean Dynamic Topography (UTM20 MDT) models around Malaysian seas are introduced in this study. These regional models are computed via scrutinizing along-track sea surface height (SSH) points and specific interpolation methods. A 1.5-min resolution of UTM20 MSS is established by integrating 27 years of along-track multi-mission satellite altimetry covering 1993–2019 and considering the 19-year moving average technique. The Exact Repeat Mission (ERM) collinear analysis, reduction of sea level variability of geodetic mission (GM) data, crossover adjustment, and data gridding are presented as part of the MSS computation. The UTM20 MDT is derived using a pointwise approach from the differences between UTM20 MSS and the local gravimetric geoid. UTM20 MSS and MDT reliability are validated with the latest Technical University of Denmark (DTU) and Collecte Localisation Services (CLS) models along with coastal tide gauges. The findings presented that the UTM20, CLS15, and DTU18 MSS models exhibit good agreement. Besides, UTM20 MDT is also in good agreement with CLS18 and DTU15 MDT models with an accuracy of 5.1 and 5.5 cm, respectively. The results also indicate that UTM20 MDT statistically achieves better accuracy than global models compared to tide gauges. Meanwhile, the UTM20 MSS accuracy is within 7.5 cm. These outcomes prove that UTM20 MSS and MDT models yield significant improvement compared to the previous regional models developed by UTM, denoted as MSS1 and MSS2 in this study

Accuracy assessment of quasi-seamless hydrographic separation models in Malaysian waters

The hydrographic survey reduction using ellipsoid has been available since the advent of the global navigation satellite system (GNSS), with a potential to streamline operation and enhance bathymetric output. Spatially continuous separation surfaces connecting a chart datum (CD) to a geodetic ellipsoid is required for this technique. Universiti Teknologi Malaysia (UTM) has invented a new quasi-seamless separation model for Malaysian waters, known as the Malaysian Vertical Separation (MyVSEP) model, through semi-empirical models to capture the spatial variability of a tidal datum between coastal and offshore areas. A continuous vertical datum is established to develop MyVSEP models by combining the coastal and offshore datasets. The coastal datasets referred to the vertical reference point computed from coastal tide gauges, while the offshore datasets referred to the vertical reference surfaces derived from satellite altimetry. Mean sea level (MSL) or mean sea surface (MSS), mean dynamic topography (MDT), lowest astronomical tide (LAT), and highest astronomical tide (HAT) are the vertical datums involved in developing the continuous MyVSEP model. However, the integration of the vertical datum has only been conducted over the Peninsular Malaysia region. For Sabah and Sarawak, datum integration cannot be implemented due to the limitation of coastal datasets. The assessment of the integrated vertical datum with coastal tide gauges is discussed in this study. The finding shows that the root mean square error (RMSE) agreement between the integrated Universiti Teknologi Malaysia 2020 (iUTM20) model and coastal tide gauges yields below 2.0 cm. The iUTM20 lowest astronomical tide and highest astronomical tide models also show significant improvement compared to the altimetric-derived tidal models, which recorded the root mean square error agreement with coastal tide gauges of 1.8 cm and 2.0 cm, respectively. The development of a continuous vertical separation model for the Ellipsoidally Referenced Surveying technique indirectly optimizes marine geospatial information resources, especially for the National Hydrographic Centre in Malaysia

Derivation of sea level anomaly based on the best range and geophysical corrections for Malaysian seas using radar altimeter database system (RADS)

The utilization of satellite altimeter data sets from previous and present satellite altimeter missions is imperative to both oceanographic and geodetic applications. The important parameter that can be derived from satellite altimeter is sea level anomaly, while it is also fundamental for sea level monitoring, geoid determination and current circulations study. This paper presents an effort to determine sea level anomaly for Malaysian seas from six satellite altimeter missions; TOPEX, JASON1, JASON2, ERS1, ERS2 and ENVISAT. The best range and geophysical corrections for Malaysian seas were also investigated in this study by evaluating two state of the art corrections available for 9 years of TOPEX satellite altimeter (from January 1993 to December 2001). Sea level data retrieval and reduction were carried out using the Radar Altimeter Database System (RADS). The comparison of near-simultaneous altimeter and tide gauges observations showed good agreement with the correlations are higher than 0.87 at Tioman Island, Langkawi Island and Kota Kinabalu. This paper introduces RADS and deals with determination of sea level anomaly using the best range and geophysical corrections in Malaysian sea

Refinement of gravimetric geoid model by incorporating terrestrial, marine, and airborne gravity using KTH method

We compute a new gravimetric geoid model for Peninsular Malaysia (PMGG2020) based on the Royal Institute of Technology (KTH) method. The PMGG2020 was computed from 8474 terrestrial gravity points, satellite altimetry-derived gravity anomaly (DTU17), 24,855 airborne gravity data, and the TanDEM-X Digital Elevation Model. All the gravity datasets were combined and gridded onto a 1-min resolution using the 3D Least Square Collocation (LSC) method with EIGEN-6C4 as the reference field. GO_CONS_GCF_2_SPW_R4 was used to provide long wavelengths of gravity field up to 130 maximum degrees and order in the geoid computation. Based on an evaluation using 173 Global Navigation Satellite System (GNSS)-levelling points distributed over Peninsular Malaysia, the precision of the PMGG2020 was 0.058 m. It is almost identical to the accuracy of the official Peninsular Malaysia gravimetric geoid, WMG03A. Using airborne gravity, the precision of PMGG2020 showed a significant improvement of ~4 cm over the existing KTH-derived geoid model, PMSGM2014. These results highlight the significant effect of airborne gravity data on the accuracy of the geoid model

Public understanding of rip current and beach safety at Teluk Cempedak Recreational Beach in Pahang, Malaysia

Rip currents are known to be a global public health issue and have been extensively contributed to the coastguard rescues and drowning cases at recreational beaches. Most studies in Malaysia have focused on the physical control of rip currents, with little emphasis on social factors. This study aims to assess the public knowledge of rip currents and beach safety at Teluk Cempedak Recreational Beach (TRCB) in Pahang, Malaysia. A convenience sampling technique was used to conduct a cross-sectional study among 300 beachgoers in TCRB. All data was collected using a self-administered questionnaire. Bivariable and multivariable logistic analyses were computed to identify factors associated with satisfactory knowledge of rip current and beach safety. More than half of the respondents were females (51%) and residents of Kuantan (62%). Out of 300 respondents, 160 (53.3%) had a satisfactory knowledge of rip currents, while a higher number of respondents (n = 221, 73.7%) had an unsatisfactory knowledge of beach safety. Those aged 35 and up, females, and those who had never had difficulty with water activities at the beach were more likely to have satisfactory knowledge of rip currents. The only factor found to be significantly related to satisfactory beach safety knowledge was age (35 years old). In conclusion, the respondents were concerned about rip currents, but they had inadequate knowledge of beach safety. Therefore, the development of effective beach safety education programmes is needed in Malaysia

DataSheet1_Accuracy assessment of quasi-seamless hydrographic separation models in Malaysian waters.pdf

The hydrographic survey reduction using ellipsoid has been available since the advent of the global navigation satellite system (GNSS), with a potential to streamline operation and enhance bathymetric output. Spatially continuous separation surfaces connecting a chart datum (CD) to a geodetic ellipsoid is required for this technique. Universiti Teknologi Malaysia (UTM) has invented a new quasi-seamless separation model for Malaysian waters, known as the Malaysian Vertical Separation (MyVSEP) model, through semi-empirical models to capture the spatial variability of a tidal datum between coastal and offshore areas. A continuous vertical datum is established to develop MyVSEP models by combining the coastal and offshore datasets. The coastal datasets referred to the vertical reference point computed from coastal tide gauges, while the offshore datasets referred to the vertical reference surfaces derived from satellite altimetry. Mean sea level (MSL) or mean sea surface (MSS), mean dynamic topography (MDT), lowest astronomical tide (LAT), and highest astronomical tide (HAT) are the vertical datums involved in developing the continuous MyVSEP model. However, the integration of the vertical datum has only been conducted over the Peninsular Malaysia region. For Sabah and Sarawak, datum integration cannot be implemented due to the limitation of coastal datasets. The assessment of the integrated vertical datum with coastal tide gauges is discussed in this study. The finding shows that the root mean square error (RMSE) agreement between the integrated Universiti Teknologi Malaysia 2020 (iUTM20) model and coastal tide gauges yields below 2.0 cm. The iUTM20 lowest astronomical tide and highest astronomical tide models also show significant improvement compared to the altimetric-derived tidal models, which recorded the root mean square error agreement with coastal tide gauges of 1.8 cm and 2.0 cm, respectively. The development of a continuous vertical separation model for the Ellipsoidally Referenced Surveying technique indirectly optimizes marine geospatial information resources, especially for the National Hydrographic Centre in Malaysia.</p