Zulkarnaini Mat Amin

Accuracy Assessment of TanDEM-X DEM and Global Geopotential Models for Geoid Modeling in the Southern Region of Peninsular Malaysia

In modeling of geoid model, global digital elevation models (GDEMs) and global geopotential models (GGMs) involve in most part of the geoid computation process. Any errors in GDEMs and GGMs will introduce errors directly in geoid computation. Therefore, this study aims to evaluate the six recent GGMs and new digital elevation model from TanDEM-X, as well as the previously available GDEMs, SRTM GDEMs, over the southern region of Peninsular Malaysia. The evaluation of GDEMs has been performed with the use of high-precision Global Navigation Satellite System (GNSS) and EGM96 as vertical reference consisting of 277 stations. Meanwhile, the evaluation of GGMs is carried out using sixty-two (62) collocated GPS/leveling benchmarks (BMs). Based on the statistical analysis, it is shown that the improvement of DEM from TanDEM-X data is compared to the previously available DEMs, SRTM GDEMs. DEM from TanDEM-X of 30-m arc resolution is much better than TanDEM-X of 12-m arc resolution, as well as SRTM 30m and 90m. Comparison of GGMs with GNSS leveling shows that geoid height from GOCO05c fits well with the local geoid model.

Gravimetric geoid modeling in the northern region of Peninsular Malaysia (NGM17) using KTH method

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 Earths 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.

Conventional total station versus digital photogrammetry in land development Applications

In land development, the need for up to date planimetric plans is emphasised. Numerous techniques can be used to produce these plans such as traditional photogrammetry, satellite photogrammetry and terrestrial surveying using total station or Global Positioning System (GPS) techniques. However, for the purpose of this paper, GPS and total station are used together with photogrammetric techniques. GPS was used to establish ground control points for aerial triangulation in photogrammetry. Some selected portions within the campus of Universiti Teknologi Malaysia (UTM) are chosen to carry out this integration mapping [1]. Field surveying technique using total station is always adopted as a traditional method for planimetric plan production and mapping of urban and rural areas. Both the conventional surveying i.e., Total station and photogrammetry could be used for surveying purposes but the accuracy and techniques of each method differs from one another, hence in this project, both techniques are looked at in order to compare and draw some inferences. The main objectives will be to produce planimetric plan of the study area using conventional surveying technique (i.e., total station) and photogrammetric method to perform analysis of the two surveying methods.

Analysing Petroleum Leakage from Ground Penetrating Radar Signal

The current evolution of technologies and rapid development has influenced the pipeline construction all over the world. However, this development can be a risk to the surrounding environment, for example pipeline leakage. There are numerous incidents that caused by pipeline leakage, which includes petroleum pipeline leakage. The petroleum pipeline leakage is one of the very serious situations that can lead to the explosion and the worst it can cause disaster to the nearby area and loss of life. There are numerous methods that are used to detect underground pipeline leaks. One of the methods is Ground-Penetrating Radar (GPR). This study investigates the petroleum leakage and its impact to the surrounding soil. The objectives of this study are to determine the physical properties of the contaminated soil and to evaluate the numerical analysis of the electromagnetic wave for petroleum leakage diffusion in sand. The prototype of leakage model has been built for simulating observation. The data have been collected for every hour for 16 h to monitor the petroleum leakage diffusion. The software used to process and extract GPR data is Reflex 2DQuick. Furthermore, the Finite Difference Time Domain (FDTD) method was used for the simulation of the petroleum leakage diffusion by simulating the electromagnetic waves penetrating through different materials. GPR signal modelling and numerical analysis were done in MATGPR software. The result of this study indicates the changes of dielectric constant of sand from 3 to 5.3 when the sand is mixed with petroleum. The increase in dielectric properties of sand is due to its ability to store the electrical energy. Moreover, the result of GPR signal modelling proves that the content of petroleum has disturbed the signal attenuation which is transmitted by the antenna.

Three-Dimensional Stratigraphy View from Ground Penetrating Radar Attributes for Soil Characterization

The Ground Penetrating Radar (GPR), a geophysical technique that uses non-destructive testing to detect objects and structure beneath the soil was a huge contribution in survey and engineering, especially in underground utility. GPR has been used since 1970 and the method is still undergoing upgrade alongside the sophisticated processing software. Nevertheless, soil is the principal medium which interferes with the signal penetration of GPR due to its physical and electrical properties. Thus, a study using soil stratigraphy is a prerequisite to understanding GPR radargram. In this study, a test bed was constructed to simulate different soil layers which consist of existing clay, sand, small stone, and crusher run stone. The GPR instrument with frequencies of 100, 250, 400, 750, and 900 MHz was used to collect the data. The processing was carried out using reflex software for image interpretation and three-dimensional (3D) visualizations. This study is expected to help surveyors in understanding the measurement, for example, soil composition, problems related to GPR underground surveying.

Evaluation of Global Digital Elevation Model for Flood Risk Management in Perlis

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.

Ground Penetrating Radar's (GPR) imaging and applications to pavement structural assessment: A case of Malaysia

Traditionally, pavement distress evaluations were carried out by visual observation. Traditional practice requires a person to walk along the stretch of the pavement to conduct distress survey, take photo and measure defects occurred at deteriorated surfaces. However, this approach is too subjective, generates inconsistencies of information, less reliable and time-consuming. Due to these shortcomings, the transportation practitioners in pavement maintenance seek for other alternative tools and techniques to arrest incapability of traditional practices. One of the tools available in the market is Ground Penetrating Radar (GPR). GPR is a geophysical tool known by ability to accommodate extensive data in pavement assessment, geotechnical investigation and structural assessment. The application of GPR is such new to most of road maintenance industry in Malaysia. Therefore, this study has been undertaken to evaluate the benefits of using GPR imaging and its application in assessing pavement structures in Malaysia. The GPR survey was conducted in Meranti street located at UTM (Universiti Teknologi Malaysia) campus, and then analyzed using REFLEX 2D simulation software. The finding shows there are three (3) types of information obtained from GPR survey included; identification of raw image and processed image, identification of pavement segments thickness, and identification of GPR response towards surface and subsurface conditions, which illustrated in radargram images. Furthermore, the GPR can perform at high speed and can save time. It is also beneficial for long-term investment due to ability to provide extensive information at a greater depth. The research indicates that interpretation of GPRs radargram images consumes time due to the low resolution. Therefore, selection of GPR system is subject to level of accuracy and clarity of radar images needed in a project.