Spatio-temporal estimation of integrated water vapour over the peninsular malaysia

Located at a low latitude region, Peninsular Malaysia experiences extreme rainfall and hot weather over various places. The region has a large amount of water vapour in the atmosphere, and its variation shows a close relationship with the monsoon season, leading to severe flood events in some states during the season. Hence, it is important to classify the homogenous characteristic of atmospheric water vapour over this region. However, observing atmospheric water vapour over climatology time period is difficult to enumerate due to its high variability in time and space. Thus, characterizing the water vapour behaviour in the troposphere based on horizontal profile by using Global Positioning System (GPS) meteorology approach has been widely adopted by researchers. However, in this low-latitude region, only a few studies have been conducted due to the lack of GPS Continuously Operating Reference Stations (CORS) infrastructure co-located with the meteorological sensors in this area. Therefore, the aim of this study is to define the behaviour of water vapour in Peninsular Malaysia by utilizing ground-based GPS networks. Three objectives were established for three different research phases. The first objective is to estimate the Zenith Path Delay (ZPD) and Integrated Water Vapour (IWV) from the network of GPS stations. The estimation process of ZPD was performed in post-processed mission and the results were validated with ZPD product by International GNSS Service (IGS). The Root Mean Square (RMS) errors of the GPS-derived ZPD lie between 6 mm to 19 mm. From ZPD, the value of GPS-derived IWV was further extracted and validated with IWV from selected radiosonde stations. Based on the findings, Peninsular Malaysia has high amount of water vapour with an average of >50 kg/m2 over the year. Three GPS stations close to radiosonde stations were assessed and the RMS errors of the GPS-derived IWV were 9.914 kg/m2, 11.154 kg/m2 and 9.865 kg/m2. The results present a good relationship between GPS and radiosonde IWV with linear correlation coefficients of 0.9116, 0.8245 and 0.8369, respectively. The validation results are then addressed in the second phase of the study to fulfil the second objective, which is to assess the estimated GPS ZPD and IWV. The third objective is to characterize the spatio-temporal variability of water vapour in Peninsular Malaysia during monsoon seasons. Two-dimensional (2D) water vapour mapping was generated from IWV results to achieve this objective. Based on the mapping, it was found that the high amount of water vapour can be seen over the west coast of Peninsular during First Inter Monsoon (FIM) with a mean average ranges from 45.482 kg/m2 to 52.973 kg/m2. During the Second Inter Monsoon (SIM) the value of GPS-derived IWV depicts a higher amount of water vapour with a maximum value recorded at 57.429 kg/m2. Further analysis show that North and Northeast of Peninsular Malaysia experienced more water vapour during South West Monsoon (SWM): the mean average lies between 50.505 kg/m2 to 53.305 kg/m2. During North East Monsoon (NEM), less amount of water vapour was recorded in the Northwest and East of Peninsular Malaysia (a mean average of 43.851 kg/m2 to 54.548 kg/m2). However, heavy rain is common in the season, possibly due to the strong monsoon wind that caused the affected area to receive substantial high amount of rainfall. This study has successfully demonstrated the positive trend between GPS-derived IWV and rainfall data

Ionospheric residual analysis for network-RTK in low-latitude area: towards solar cycle 24

Network-RTK positioning technique has been proven efficient to ameliorate a significant portion of spatially correlated errors over its coverage. Amongst them, the dispersive effect of ionosphere, which exhibits dynamic spatial and temporal variations, remains the largest error contributor in GPS positioning. Dispersive network residuals are expected to increase towards Solar Cycle 24. Investigation in ISKANDARnet found that the behaviour of equatorial ionospheric residuals reveals noticeable correlation with geomagnetic storm outburst

Modeling of the communication link for data correction in network-rtk

The current communication in several network-RTK systems is frame relay technology that applied packet switching network (leased line) based on IPVPN which services data transmission between reference stations to control station. The most significant shortcoming of frame relay technology is depend on cabling networks and bandwidth limitation that is not effective for the rural or suburban area. In other hand the channel speed of frame relay is relative small for data transmission. This limitation has an effect on bandwidth, cost and time delay of the data transmission. In this paper we propose the system model of the 3G technology that is capable to overcome cabling dependency due to complicated installation, cost and time delay due to low data rate that will be applied for Network-RTK system in Metro-Area of Iskandar Malaysia. 3G technologies offer users a wider range of more advanced services while achieving greater network capacity through improved spectral efficiency. Services include widearea wireless voice telephony, video calls, and broadband wireless data, all in a mobile environment. It can be expected by applying of 3G technology in network-RTK, the performance system of real time data transmission are improved in bandwidth capacity, channel speed and diminish the expenditure of cablinginstallation

Investigating the application of pixel-level and product-level image fusion approaches for monitoring surface water changes

The aim of this paper was to investigate the suitability of the pixel-level and product-level image fusion approaches to detect surface water changes. In doing so, firstly, the principal component analysis technique was applied to Landsat TM 2010 multispectral image to generate the PC components. Several pixel-level image fusion techniques were then performed to merge the Landsat ETM+ 2000 panchromatic with the PC1PC2PC3 band combination of Landsat TM 2010 imagery to highlight the surface water changes between the two images. The suitability of the resulting fused images for surface water change detection was evaluated quantitatively and visually. Finally, the support vector machine (SVM) technique was applied to the qualified fused images to map the highlighted changes. Furthermore, a product level fusion (PLF) approach based on various satellite-derived indices was employed to detect the surface water changes between ETM+ 2000 and TM 2010 images. The accuracy of the resulting change maps was assessed based on a reference change map produced using visual interpretation. The results demonstrated the effectiveness of the proposed approaches for surface water change detection, especially using the Gram Schmidt-SVM, PLF-NDWI, and PLF-NDVI methods which improved the accuracy of change detection over 99.70

Performance of site velocity prediction in Sundaland

Global Positioning System (GPS) technique has been extensively implemented in determination of crustal deformation globally. With the ability of providing solution up to milimeter (mm) level, this technique has proven to provide a precise estimate of site velocity that represents the actual motion of tectonic plate over a period. Therefore, this study aims to evaluate the site velocity estimation from GPS-derived daily position of station, respective to the global plate motion model and predicted site velocity via Least-Squares Collocation (LSC) method within the tectonically active region of Sundaland. The findings have indicated that stations with precise velocity estimates were consistent with global plate model and predicted velocity, with velocity residuals of 5 mm - 10 mm. However, stations that were severely impacted by continuous earthquake events such as in Sumatra were believed to be induced by the impact with consistently large velocity residuals up to 37 mm. Following the outcomes, this study has provided an insight on the post-seismic decay period plate motion which are induced by continuous tectonic activities respective to modelled plate motion

Reliability of the GPS carrier-phase fix solution under harsh condition

Once the unknown integer ambiguity values are resolved, the GPS carrier phase observation will be transformed into a millimeter-level precision measurement. However, GPS observation are prone to a variety of errors, making it a biased measurement. There are two components in identifying integer ambiguities: estimation and validation. The estimation procedure aims to determine the ambiguity's integer values, and the validation step checks whether the estimated integer value is acceptable. Even though the theory and procedures for ambiguity estimates are well known, the topic of ambiguity validation is still being researched. The dependability of computed coordinates will be reduced if a false fixed solution emerges from an incorrectly estimated ambiguity integer value. In this study, the reliability of the fixed solution obtained by using several base stations in GPS positioning was investigated, and the coordinates received from these bases were compared. In a conclusion, quality control measures such as employing several base stations will improve the carrier phase measurement's accuracy

Smart water network monitoring: A case study at Universiti Teknologi Malaysia

Water uses need to be measured, which is critical for evaluating water stress. The Industry 4.0 via the Internet of Things (IoT) and usage of water measurement sensor can provide real-time information on the water flow rate and water pressure, that is crucial for water monitoring and analysis. There is a need for online smart water monitoring that gives out more efficient and sustainable water uses at Universiti Teknologi Malaysia (UTM) campus. A prototype of an online smart water monitoring for UTM, which was developed based on the integration of IoT and Geographical Information System (GIS), consist of four layers, (1) physical layer, (2) network layer, (3) processing layer and, (4) application layer. The findings show that when the water flow increases, the water pressure decreases. When there is no water flow, the lowest value is 52.214 Psi, and the highest value is 60.916 Psi. The latest technology integrating the IoT-GIS for smart water monitoring has shown a very efficient way of providing real-time water parameters information, cost and time effective, and allowing for continuous water consumption analysis via the cloud computing service

Influencing factors on the accuracy of local geoid model

Different modification methods and software programs were developed to obtain accurate local geoid models in the past two decades. The quantitative effect of the main factors on the accuracy of local geoid modeling is still ambiguous and has not been clearly diagnosed yet. This study presents efforts to find the most influential factors on the accuracy of the local geoid model, as well as the amount of each factor's effect quantitatively. The methodology covers extracting the quantitative characteristics of 16 articles regarding local geoid models of different countries. The Statistical Package of Social Sciences (SPSS) software formulated a strong multiple regression model of correlation coefficient r = 0.999 with a high significance coefficient of determination R2 = 0.997 and adjusted R2 = 0.98 for the required effective factors. Then, factor analysis is utilized to extract the dominant factors which include: accuracy of gravity data (40%), the density of gravity data (25%) (total gravity factors is 65%), the Digital Elevation Model (DEM) resolution (16%), the accuracy of GPS/leveling points (10%) and the area of the terrain of the country/state under the study (9%). These results of this study will assist in developing more accurate local geoid models

Spatial and seasonal ionospheric error growth in DGPS measurement: a case study in Malaysia

This paper tackles the Equatorial ionosphere and its effects on Differential Global Positioning System (DGPS) error growth over Malaysia by using a network of GPS Continuously Operating Reference Stations (CORS). Seasonal variation of ionospheric delay has been examined and findings show that the effect of spatial variation of ionospheric errors in DGPS is very significant during the equinoctial seasons. Furthermore, a DGPS regression model was developed and tested during the solar maximum year in 2013 by using internet-based DGPS. The results show that the model is capable of estimating DGPS positional errors for distances of user to reference station less than 680 km