Papers by Muhammad Faiz (PhD) Pa'suya
The vertical height system in Kenya is anchored on a single levelling-based tidal gauge, which is... more The vertical height system in Kenya is anchored on a single levelling-based tidal gauge, which is referred to as mean sea level. The fusion of existing height systems into the world height system is one of the primary objectives of the International Height Reference System (IHRS) implementation. Computing the datum offset with regard to the global IHRS datum and the zero-height geopotential value can help achieve this goal in part. This paper studies the approach of using a Global Geopotential model (GGM) with the GNSS-levelling as a convenient method for vertical datum offsets' computation that may connect two or more vertical datums. To reduce the geoid omission error of the GGMs, an optimized GGM is developed and utilized up to a maximum of 3600 • and order. For the first time, the numerical analyses of this work reveal the zero-height geopotential and its associated standard error of the Kenyan vertical datum, from which the datum offsets with the IHRS were estimated. Values of 62636850.996 ± 0.104m 2 s − 2 and − 24.5 ± 1.04cm were obtained as the geopotential of the zero-height and vertical datum offset with respect to the global value, respectively.
Dìqiú kēxué jíkān, Feb 9, 2022
Marine gravity anomalies are crucial parameters and elements for determining coastal and ocean ge... more Marine gravity anomalies are crucial parameters and elements for determining coastal and ocean geoid, tectonics and crustal structures, as well as offshore studies. This study aims to derive and develop a marine gravity anomaly model over Malaysian seas from multi-mission altimetry data. Universiti Teknologi Malaysia 2020 Mean Sea Surface Model is computed based on along-track data from nine satellite missions, incorporating TOPEX, Jason-1, Jason-2, ERS-2, Geosat Follow on (GFO), Envisat-1, CryoSat-2, SARAL/AltiKa, and Sentinel-3A. The data exploited are from 1993 to 2019 (27 years). Residual gravity anomaly is computed using Gravity Software, and two-dimensional planar Fast Fourier Transformation method is applied. The evaluation, selection, blunder detection, combination, and re-gridding of the altimetry-derived gravity anomalies and Global Geopotential Model data are demonstrated. Cross-validation procedure is employed for data cleaning and quality control using the Kriging interpolation method. Then, cross-validation procedure is applied to the tapering window width 200, which adopting the GECO model denotes the optimum gravity anomaly with root mean square errors in the range of ± 4.2472 mGal to ± 6.0202 mGal. The findings suggest that the estimated marine gravity anomaly is acceptable to be implemented in the marine geoid determination and bathymetry estimation over Malaysian seas. In addition, the results of this study are valuable for geodetic and geophysical applications in marine areas. Key points • Along-track altimetry data are used for mean sea surface derivation. • Mean sea surface model is utilised in the estimation of marine gravity anomalies. • Global Geopotential Model is crucial in the marine gravity estimation of a region.
A combined regional Geopotential Model using optimized global Gravity Field Solutions
IOP conference series, Jul 1, 2022
To develop a gravimetric geoid, a Global Geopotential Model (GGM) is required to minimise the tru... more To develop a gravimetric geoid, a Global Geopotential Model (GGM) is required to minimise the truncation error arising from using the Stokes integral with a limited number of gravity data points. The choice of a best-fitting GGM determines the accuracy of a gravimetric geoid solution. Selecting a suitable GGM is a rigorous process, requiring both internal and external evaluation of all GGMs available at the International Center for Globa Earth Models (ICGEM). Moreover, GGMs perform differently depending on the wavelength, and it is difficult to obtain a GGM that performs best across the full harmonic spectrum. In this study, a combined GGM is developed from a selection of the most recent and high-resolution GGMs covering Peninsular Malaysia. The selected models are first synthesized harmonically to obtain geoid undulations at collocated GNSS-levelled points, and free air anomalies at randomly sampled points across the study area. These quantities are compared with the observed geoid undulations and point gravity anomalies interpolated from a grid of free air anomalies. The best performing GGMs are then used to produce a combined GGM, by selecting the spherical harmonic coefficients with the best characteristics for every degree. The signal and error spectra of the new GGM are compared with the selected geopotential models. The combined GGM produced a higher cumulative signal to noise ratio (SNR) of 4402.669 compared to all the selected GGMs, with XGM2016 and Eigen-6C following suit with SNR of 4139.561 and 4092.462, respectively. Besides, the new combined GGM performed better across the whole harmonic spectrum than all selected GGMs. The use of combined GGMs in geoid modelling, instead of a single GGM may be more desirable because they can improve the quality of results.
A Review on Global and Localised Coverage Elevation Data Sources for Topographic Application
IOP conference series, Jul 1, 2022
International Journal of Integrated Engineering, Sep 6, 2022
The evaluation towards global geopotential models represents a significant part in modelling the ... more The evaluation towards global geopotential models represents a significant part in modelling the localised Marine Geoid. The marine geoid provides the vertical reference information in Marine Spatial Data Infrastructures (MSDI) development response to United Nations Sustainable Development Goals 14 for the sustainable development in marine environment. The main purpose of this study is to select the best model from both combined missions and satellite-only missions for the Malaysian region. The gravity anomaly field from 30 global models were exclusively calculated over the selected study area within 11 years period-time. Afterwards, each dataset was extracted from the ICGEM server to evaluate with the airborne-derived gravity anomaly from the Department of Surveying and Mapping, Malaysia. The internal accuracy, root mean square error (RMSE) and differences between every model and airborne data were computed. The result indicates GGM-derived gravity anomaly for the best combined mission is GECO with RMSE of 8.44 mGal and the standard deviation value of 28.034 mGal. While, the model from Gravity field and steady state Ocean Circulation Explorer (GOCE) namely, the GO_CONS_GCF_2_DIR_R5 is the best for the satellite-only mission with RMSE of 17.43 mGal and the standard deviation value of 22.828 mGal. As a conclusion, GECO model is preferred as the best fit for determining the marine geoid as it has the lowest RMSE value between both mission and the maximum degree of 2109 o coverage. The finding can assist in development of marine geoid for modelling precise surface elevation.
Hybrid geoid model over peninsular Malaysia (PMHG2020) using two approaches
Studia Geophysica Et Geodaetica, Oct 1, 2022
A level Ellipsoid for modelling regional Gravity Field
Modern, very precise gravity models are now being created in the discipline of geodesy, using pur... more Modern, very precise gravity models are now being created in the discipline of geodesy, using purely satellite techniques. Thanks to the GOCE and GRACE missions, high quality global gravitational models have been computed and made available to users. The models allow for the derivation of gravity field functionals when coupled with reference equipotential normal ellipsoids, such as GRS80 and WGS84. These ellipsoids represent the global fit to the geoid, but may depart from the geoid in local circumstances. The precision of computed gravimetric field functionals depends on the fit of the reference model to the geoid. In this study, a regional normal ellipsoid that fits the local geoid is computed from terrestrial data, using both ordinary and combined least squares optimization techniques, applying the theory of equipotential ellipsoid. Results from the combined model were used to compute the geometrical and physical constants of the new ellipsoid A normal ellipsoid, with semi-major ...
Public understanding of rip current and beach safety at Teluk Cempedak Recreational Beach in Pahang, Malaysia
Natural Hazards
Improving the Accuracy of Local Gravimetric Geoid Modelling Using Simulated Terrestrial Gravity Data
Pure and Applied Geophysics
Accuracy assessment of open-source global digital elevation models (GDEMs) with global navigation satellite system (GNSS) levelling
IOP Conference Series: Earth and Environmental Science
Shuttle Radar Topography Mission (SRTM), Advanced Spaceborne Thermal Emission and Reflection Radi... more Shuttle Radar Topography Mission (SRTM), Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER ), Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010), Advanced Land Observing Satellite World-3D (ALOSW3D), and TerraSAR-X Digital Elevation Measurement (TanDEM-X) are open-source Digital Elevation Model (DEM) datasets for environmental modelling and studies. The spatial resolution and vertical accuracy of DEM data sources play a significant role, particularly in dealing with land inundation, periodic flooding, and coastal erosion. In this study, the comparison between orthometric height, H from Global Navigation Satellite System (GNSS) observation, and DEM is performed to evaluate the accuracy of each DEM in terms of their Root Mean Square Error (RMSE) and correlation coefficient, R2 for monitoring the coastline. The result has indicated that TanDEM-X shows the smallest RMSE of 2.574 m compared to SRTM30, SRTM90, ASTER, GMTED10, and ALOSW3D with RMSE of 2.968...
Accuracy assessment of the tandem-X DEM in the northwestern region of peninsular Malaysia using GPS-levelling
This study provided a unique accuracy assessment of the TanDEM-X DEM and two other DEMs; SRTM and... more This study provided a unique accuracy assessment of the TanDEM-X DEM and two other DEMs; SRTM and AW3D30; using three sets of GPS data around northwestern Peninsular Malaysia. Firstly, the absolute vertical accuracy of all DEMs provided by Department Survey and Mapping Malaysia (DSMM) was examined by 7755 ground control points (GCPs), which were distributed across the northwestern region. The root-mean-square error (RMSE) of 3.980m and mean error of 2.464m indicated a good agreement of TanDEM-X DEM and GCPs, followed by AW3D30 (RMSE=5.206m) and SRTM (RMSE=6.684m). Secondly, the vertical accuracy assessment of TanDEM-X DEM and the others two DEMs was conducted by comparing the elevation of GPS data around four different land-covers; coastal, hills, foothills and agriculture to study the effects of different land-covers to DEMs accuracy. Again, at the coastal, foothills and agriculture region, TanDEM-X DEM showed the lowest RMSE of 0.66m, 3.8m and 0.41m, respectively. Surprisingly, the accuracy of TanDEM-X DEM at the hill region was lower than those of AW3D30 and SRTM DEM with RMSE of 55.51m. This study also managed to assess the best geoid model to convert the elevation of TanDEM-X DEM to the orthometric height. Three geoid models were tested using local mean sea level at 38 Benchmark around the Perlis region. The results showed that the Malaysia geoid model, MyGEOID, gave the lowest RMSE of 2.277m, followed by EGM2008 (RMSE=2.504m) and EGM96 (RMSE=2.675m)
The implementation and advancement of a regional geodetic vertical datum
IOP Conference Series: Earth and Environmental Science, 2021
The essential parameter in computing three-dimensional coordinate system is the height or depth o... more The essential parameter in computing three-dimensional coordinate system is the height or depth of the Earth’s surface. It represents a particular reference surface that recognised as a vertical datum. The vertical datum is alienated into two foremost categories recognised as Mean Sea Level and Lowest Astronomical Tide. Different modifications approach, techniques and software programs are developed to determine vertical datum of a region with respect to geoid surface. This paper presents an effort to review and discuss the implementations and advancement of geodetic vertical datum based on geoid height reference surface. Hence, there are eight countries will be extracted and outlined in this paper consist of the United States of America, Australia, Taiwan, New Zealand, South Korea, Thailand, Philippines and Malaysia. An overview of geodetic vertical datum which implemented in these countries are summarised to support the future development of a regional vertical datum model. Then, ...
Deriving offshore tidal datums using satellite altimetry around Malaysian seas
IOP Conference Series: Earth and Environmental Science, 2021
Tidal datums are important for calculating spatial coordinates especially the elevation relative ... more Tidal datums are important for calculating spatial coordinates especially the elevation relative to mean sea level and also crucial for defining the state sovereignty boundaries over maritime areas. Normally, sea level was measured by tide gauges along the coastal for tidal datums computation. However, knowledge of tides is still restricted in coastal areas. Furthermore, tidal range at offshore was simply assumed to be similar as coastal due to the difficulties installing offshore tide gauges. The launching of satellite altimeter technologies with precise orbit determination since 1993 had provided significant accuracy of sea surface height (SSH) measurements. The observed SSH from satellite altimetry can be offered as tide gauge measurements at each location globally. This study aims to derive offshore tidal datums using satellite altimetry around Malaysian seas. SSH time series from TOPEX, Jason-1, Jason-2 and Geosat Follow On (GFO) were analysed using harmonic analysis approach t...
Journal of Information System and Technology Management, Dec 1, 2021
This work is licensed under CC BY 4.0 The description of the earth's gravity field is usually exp... more This work is licensed under CC BY 4.0 The description of the earth's gravity field is usually expressed in terms of spherical harmonic coefficients, derived from global geopotential models. These coefficients may be used to evaluate such quantities as geoid undulations, gravity anomalies, gravity disturbances, deflection of the vertical, etc. To accomplish this, a global reference normal ellipsoid, such as WGS84 and GRS80, is required to provide the computing reference surface. These global ellipsoids, however, may not always provide the best fit of the local geoid and may provide results that are aliased. In this study, a regional or localized geocentric level ellipsoid is used alongside the EGM2008 to compute gravity field functionals in the state of Johor. Residual gravity field quantities are then computed using GNSS-levelled and raw gravity data, and the results are compared with both the WGS84 and the GRS80 equipotential surfaces. It is demonstrated that regional level ellipsoids may be used to compute gravity field functionals with a better fit, provided the zero-degree spherical harmonic is considered. The resulting residual quantities are smaller when compared with those obtained with global ellipsoids. It is expected that when the removecompute-restore method is employed with such residuals, the numerical quadrature of the Stoke's integral may be evaluated on reduced gravity anomalies that are smoother compared to when global equipotential surfaces are used
A cross-sectional study was conducted to examine the public understanding of rips currents at Tel... more A cross-sectional study was conducted to examine the public understanding of rips currents at Teluk Cempedak Recreational Beach of Pahang, Malaysia, from November 2020 to March 2021 via a questionnaire survey. Convenient sampling was used to collect data from 300 respondents. The questionnaire consisted of 24 questions, encompassing ve sections, i.e., the demographic background, frequency of visiting the beach, swimming ability, their knowledge of rip currents, and understanding of beach safety. Associations between the study variables and the knowledge of both rip currents and beach safety were evaluated using the independent sample t-test, Chi-square test, and multiple logistic regressions at the con dence level of 0.05. In general, only 86% of the respondent knew about the rip currents. For beach safety knowledge, 83% of the respondents on the lifeguard facilities, 44% for the yellow red-ag and 93.7% for the red ag. Variables such as gender (knowledge of rip currents: Adjusted Odds Ratio (AOR) = 0.647, 95% con dence interval (CI) = 0.487-0.60, p = 0.003; beach safety: AOR = 0.665, 95% CI = 1.14-5.02, p = 0.021), locality (knowledge of rip currents: AOR = 2.482, 95% CI = 1.407-4.380, p = 0.002, beach safety: AOR = 1.821, 95% CI = 1.022-3.245, p = 0.042), and respondents' experience of having problems in water activities (knowledge of rip currents: AOR = 0.170, 95% CI = 0.635-6.379, p = 0.000) were signi cantly associated with the knowledge of both rip currents and beach safety. Further studies are essential to enhance public understanding of rip currents and hence the beach safety in Malaysia.
Rigorous evaluation of global geopotential models for geoid modelling: A case study in Kenya
Journal of African Earth Sciences
Developing a gravimetric geoid model requires gravity data covering the whole surface of the eart... more Developing a gravimetric geoid model requires gravity data covering the whole surface of the earth. In practice, terrestrial data within a spherical cap is used, causing a truncation error, which may be minimised if the terrestrial data is combined with a Global Geopotential Model (GGM). The choice of a GGM that fits the observed terrestrial data best, determines the accuracy of a gravimetric geoid solution. In this study, the most recent and high-resolution GGMs are selected and compared, both geometrically and spectrally with a view to selecting an optimum GGM for future geoid modelling in Kenya. In the first step, thirty-one GGMs are evaluated using 55 GNSS-levelled points scattered over 4 regions and gravity data distributed over the entire territory of Kenya. In the second step, some of the best performing GGMs are further compared using the spectral information contained in their spherical harmonic coefficients. After removal of systematic errors, the EGM2008 model showed some advantage over other GGMs with a standard deviation of 40.89 cm. Other high-resolution geoid models perform well in terms of recovering geoid heights in Kenya with a standard deviation of <42 cm. In terms of residual gravity anomalies, the EIGEN-6C4 model showed the best fit with a standard deviation of 6.892 mGal. In the spectral analysis, the XGM2016 provided the best results among the models evaluated. Based on the overall performance in all areas of evaluation, the SGG-UGM-1 and SGG-UGM-2 were considered best for geoid modelling in Kenya.
Spatial Mapping and Analysis of Carbon Dioxide Emissions from Electricity in UiTM Perlis for Assessment of Low Carbon Campus
Proceedings of the Second International Conference on the Future of ASEAN (ICoFA) 2017 – Volume 2, 2018
The increase of energy usage is the cause of greenhouse gas emission, especially carbon dioxide. ... more The increase of energy usage is the cause of greenhouse gas emission, especially carbon dioxide. Furthermore, one of the factors of high carbon emission is electricity, which is one of the energy sources needed for campus activities. The aim of this study is to analyse the amount of carbon dioxide emissions produced by the source of electricity in UiTM Perlis, for the assessment of low carbon dioxide compliance in campus. There are three types of data utilized, which are total electric consumptions in UiTM Perlis from 2013 to 2015, the building plan of UiTM Perlis, the base map of UiTM Perlis and the spatial analysis of (GIS) geographical information system. The assessment of low carbon in campus is based on the calculation of the amount of carbon dioxide emission, and it is then mapped based on five building categories. The total consumption of electrical energy by the buildings is used to determine the amount of carbon emission using the formula for carbon dioxide emission. Carbon dioxide emissions per unit square meter (ktCO2)/m2 in the three years in UiTM Perlis are 58.34, 56.24 and 55.31, respectively. Based on the comparison of these results with carbon dioxide emission guideline per unit square meter (ktCO2)/m2 which is 56.5 ktCO2, it can be seen that UiTM Perlis complies with the guideline for year 2014 and 2015.
Journal of Information System and Technology Management, 2021
Height or depth on the surface of the Earth is the crucial element in the three-dimensional coord... more Height or depth on the surface of the Earth is the crucial element in the three-dimensional coordinate system. Commonly, the height or depth value will denote a particular reference surface known as a vertical datum. Conventionally, the vertical datum is divided into two major categories which are Geoid/ Mean Sea Level and Lowest Astronomical Tide. This paper is an effort to review the applications of geodetic vertical datum from American, Australia, Taiwan, New Zealand, South Korea, and Peninsular Malaysia. An overview of geodetic vertical datum will be summarised to support the future application. Thus, a review consisting of a data gathering, data input, and analysis approach in vertical datum applications will be discussed and outlined. This initiative is significant for the planning and advancement of future vertical datum development in Malaysia.
Gravimetric geoid modeling in the northern region of Peninsular Malaysia (NGM17) using KTH method
IOP Conference Series: Earth and Environmental Science, 2018
In this study, a new geoid model for the northern region of Peninsular Malaysia (NGM17) was compu... more In this study, a new geoid model for the northern region of Peninsular Malaysia (NGM17) was computed using an alternative method known as the Least Squares Modification of Stokes formula (LSMS) with Additive Corrections (AC) or commonly called the KTH method. The NGM17 geoid was derived from the recent terrestrial gravity data provided by Department of Surveying and Mapping Malaysia (DSMM), the most recent global digital elevation model ALOS World 3D (AW3D-30) GDEM, global geopotential model (GGM) derived from three satellite gravity missions, marine gravity anomalies extracted from DTU 10 Global Gravity Field and WGM2012 Earth's gravity anomalies. The gravimetric geoid model derived in this study (NGM17) as well as the geoid obtained from DSMM were then evaluated against the GNSS-levelling data. The statistical analysis obtained shows that NGM17 gives slightly better accuracy with the mean error of NGM17 and DSMM geoid model were 0.2568m and 1.1648m respectively, and the RMSE of ?0.2686m and ?1.1656m respectively.
Evaluation of Global Digital Elevation Model for Flood Risk Management in Perlis
GCEC 2017, 2018
In flood modelling process, Digital Elevation Models (DEMs) is a valuable tool in topographic par... more In flood modelling process, Digital Elevation Models (DEMs) is a valuable tool in topographic parameterization of hydrological models. The release of the free-of-charge satellite based DEMs such as SRTM and ASTER prompted the accurate flood modelling process especially to propose flood mitigation in the Perlis region. In this research, the accuracy of SRTM DEM of spatial resolution 1 arc-sec and 3 arc-sec, as well as ASTER DEM are evaluated. The reference levels produced from GNSS observation and Earth Gravitational Model 1996 (EGM96), as well as local mean sea level are used to analyse the vertical accuracy of each GDEMs in Perlis, Malaysia. The total of 38 Benchmark (BM) and Standard Benchmark (SBM) around the Perlis region were observed by GNSS using static method and processed using TOPCON Tool software. A comparison with the local mean sea level height indicated that SRTM 1″ is the much greater absolute vertical accuracy with an RMSE of ±3.752 m and continued by SRTM 3″ and ASTER GDEMs where the obtained accuracy was ±4.100 and ±5.647 m, respectively. Also, by using orthometric height form the GNSS and EGM96 as reference elevation, the obtained accuracy was ±3.220, ±3.597, and ±5.832 m for SRTM 1″, SRTM 3″ and ASTER, respectively. Statistical results have also shown that SRTM 1″ has a good correlation with Hmsl and HGNSS where both correlations values are 0.9925, while the SRTM 3″ and ASTER show the correlation of 0.9873 and 0.9375.
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Papers by Muhammad Faiz (PhD) Pa'suya