Bathymetry estimation from satellite geodetic missions using gravity geologic method

Bathymetry information is essential in understanding the physics of the Earth and the ocean process. However, the bathymetry data are difficult to obtain at the restricted, complex and vast area. The conventional bathymetry surveys which used single beam echo sounder and multibeam echo sounder required high expenditure, consumed much time and the bathymetry data obtained were sparse. This study aims to map the bathymetry over the Malaysian seas by using the space-based approach. Six satellite missions namely Jason-1, Envisat1, ERS-2, Jason-2, Cryosat2 and Saral covering 11-year data period (2005-2015) have been used. Gravsoft software was utilised in the derivation of free air gravity anomaly (FAGA), using Fast Fourier Transform technique. Next, the derived FAGA was validated against the marine FAGA model developed by the Department of Survey and Mapping Malaysia. The Gravity-Geologic Method (G-G method) was then performed for the estimation of bathymetry and a density contrast of 1.67 g/cm3 was used. Area of the estimated bathymetry was along the latitude and longitude of 5ºN – 10ºN and 107ºE – 114.6ºE, respectively. National Geophysical Data Center shipborne data was used utilizing 12362 bathymetry data points. 6584 points were used in the G-G method process while 5778 points as the validation points (check points). Minimum curvature interpolation was utilized in establishing the regional FAGA surfaces. The assessment on the accuracy of the results obtained was made using Root Mean Square Error (RMSE) and correlation coefficient analysis. The mean sea surface height (MSSH) obtained shows a strong correlation with Technical University of Denmark 2015 MSSH model with values of 0.9980. The RMSE for the computed FAGA achieved ±11.52606 mGal, with the use of EGM2008 (full degree and order) Global Geopotential Model and with this value, it gives a reliable derived FAGA information. The final estimated bathymetry produced the RMSE value of ±96.949 m, which is estimated to be large, perhaps due to the dynamic of the ocean and the depth variations. However, this estimated bathymetry can improve the depth accuracy by approximately 69% and 38% based on the comparison made with Earth Topography 1-minute and Technical University of Denmark 2010 global bathymetry model respectively. The final estimated bathymetry is known as Universiti Teknologi Malaysia 2018 bathymetry model. The study confirms that the estimation of bathymetry using the space-based approach is reliable and the mapping of the bathymetry is more effective and time-saving as it can cover non-accessible and restricted area in a mesoscale. The information collected from satellite altimeter can be delivered to the Malaysian Bathymetry Database System as the product from this study

Generating Water Quality Maps of Klang River Based on Geographic Information System (GIS) and Water Quality Index (WQI)

Water quality index (WQI) and Geographic Information Systems (GIS) play a critical role in managing and modelling a variety of water resource issues, including urban drainage, point and non-point source pollution. Historically, the evaluation of water quality has been a domain reserved for experts, necessitating laborious and time-consuming in situ sampling and laboratory analysis. However, the integration of WQI and GIS has democratized this information, making it accessible to non-experts, thereby enhancing the comprehension of Klang River's water quality. The objective is to employ WQI and GIS to create comprehensive water quality maps. While WQI offers a straightforward numerical evaluation, the incorporation of graphical data provides a nuanced understanding of river pollution. Therefore, hourly WQI data observed at every week in 2 months from October to November 2021 over four stations (Kampung Medan, Kampung Lombong, Taman Pengkalan Batu and Jeti Sungai Udang) in Malaysia was acquired from the Selangor Maritime Gateway (SMG) website and the Malaysian National Water Quality Standard (NWQS). Adopting Inverse Distance Weighting (IDW) interpolation method, WQI parameters at unsampled locations were estimated based on values of nearby sampled points. Database was built to depict the water quality of the Klang River, particularly during the two-month monitoring. Mapping provides a clear indication of the river's water quality. The WQI mapping outcome fall between class II and class IV. The findings indicate varying water quality classes along the Klang River, revealing potential pollution sources in industrial and development areas. It was concluded from the study that the water pollution may be due to its proximity to industrial and development regions

Rerouting Framework for Sustainable Management in Elephant Conservation

: Human-Elephant Conflict (HEC) has been identified as one of the major threats to wild elephants through its range in thirteen countries including Malaysia. With development encroaching into the elephant’s natural territories, the number of HEC cases has increased. The aim of this study is focusing on developing a framework of elephant rerouting and causeway using geomatics technology and 3D Geo-visualisation as strategy to conserve elephant in sustainable way for Taman Negara Rompin. The framework was used to propose alternative pathway based on rational model. Four main elements strongly highlighted in the rerouting framework are elephant diet’s sources, tracking trail, fencing and deterrents and the corridors monitoring. With the integration of Geographical Information system, the knowledge to protect elephants from HEC can be enhanced

Contemporary sea level rise rates around Malaysia: Altimeter data optimization for assessing coastal impact

The increase of anthropogenic activities has triggered global sea level rise to threaten many low-lying and unprotected coastal areas. Without measures, global sea levels will continue to rise at an accelerating rate in the 21st century. This paper quantifies sea level trends around the Malaysian seas using measurements from multiple altimeter missions over 1993–2015. Sea level anomalies (SLAs) are determined using data from the Radar Altimeter Database System (RADS) covering 8 altimeter missions. We use an enhanced processing strategy to optimize sea surface heights from RADS for the derivation of SLAs, including filtering, data gridding and moving average. Tidal height measurements at eight tide gauge stations around Peninsular Malaysia and East Malaysia are used to assess SLAs from altimetry. Our assessment results in similar patterns of SLAs, high correlation coefficients (>0.9) and small (few cm) root mean square differences (RMSE) between SLAs from altimetry and tide gauges over the same period. Sea level trends are determined by the robust fit regression analysis for the SLA time series. Our result shows that sea level rise trends around Malaysia range from 3.27 ± 0.12 mm yr−1 off eastern Malaysia to 4.95 ± 0.15 mm yr−1 west of Malaysia. Over 1993–2015, the mean rising rate around Malaysia is 4.22 ± 0.12 mm yr−1, and the cumulative sea level rise is 0.05 m. This paper predicts the impact of such rising sea levels on environment, urban planning and climatology in the coastal areas of Malaysia