Global positioning system (GPS) positioning errors modeling using Global Ionospheric Scintillation Model (GISM)

As technology advancement progresses throughout the years in this modern age, every technology has its part to play in that the world is moving towards a brighter future. GPS (Global Positioning System) has diverse application in current globalized world, its application has pervasive benefits not only to navigation and positioning, it is pivotal in industries like logistics, shipping, financial services and agriculture. Since the decision to shut down the Selectivity Availability (SA) by former U.S. President, Bill Clinton, ionospheric effect is now the primary concern of error contributing factors in GPS. Ionospheric scintillation induces rapid fluctuations in the phase and the amplitude of received GNSS signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. Global Ionospheric Scintillation Model (GISM) was used to compute amplitude scintillation parameter for each GPS satellite visible from Melaka, Malaysia (Latitude 2° 14' N, Longitude 102° 16' E) as its location has strong equatorial scintillation behavior. The output data from GISM was then used to calculate the positioning error. There are two schemes that were used. First, the positioning error was calculated for all the visible satellites. Secondly, the positioning error was calculated for those satellite that have amplitude scintillation index, S4 <;0.7. Comparison of results from the both schemes was then made

NOAA Weather Satellite Station at KUTKM

A ground station has been installed at Kolej Universiti Teknikal Kebangsaan Malaysia (KUTKM) to receive the VHF signal form the United State National Oceanographic and Atmospheric Administration (NOAA) Low Earth Orbiting Satellite (LEO) weather satellite series. The satellite signal was received and decoded as image which was displayed on computer screen in the form of visible light, infra-red or the combination of both. The image file is then processed and stored into a local computer for meteorology study in KUTKM

Stochastic Model Considering Individual Satellite Signal Quality on GPS Positioning

Simple stochastic model is normally used in GPS positioning by making assumption that all GPS observables are statistical independent and of the same quality. By the above assumption, similar variance is assigned indiscriminately to all of the measurements. A more detail stochastic model considering specific effects affecting each observable individually may be approached such as the ionospheric effect. These effects relate to phase and amplitude measurements in satellite signals that occur due to diffraction on electron density in the ionosphere. This is particularly relevant to those regions frequent with active ionospheric event such as equatorial and high latitude regions. A modified stochastic model considering individual satellite signal quality has been implemented which based on the computation of weights for each observable. The methodology to account for these effects in the stochastic model are described and results of experiments where GPS data were processed in relative positioning mode is presented and discussed. Two weighting parameters have been used in the experiment: elevation angles and tracking error variance in the GPS receiver. The results have shown improvement of 10.3% using the elevation angles as weighting parameters and 11.5% using the tracking error variance as weighting parameter

Global Positioning System (GPS) Positioning Errors During Ionospheric Scintillation Event

As technology advancement progresses throughout the years in this modern age, every technology has its part to play in that the world is moving towards a brighter future. GPS (Global Positioning System) has diverse application in current globalized world, its application has pervasive benefits not only to navigation and positioning, it is pivotal in industries like logistics, shipping, financial services and agriculture. Since the decision to shut down the Selectivity Availability (SA) by former U.S. President, Bill Clinton, ionospheric effect is now the primary concern of error contributing factors in GPS. Ionospheric scintillation induces rapid fluctuations in the phase and the amplitude of received Global Navigation Satellite System (GNSS) signals. These rapid fluctuations or scintillation potentially introduce cycle slips, degrade range measurements, and if severe enough lead to loss of lock in phase and code. Global Ionospheric Scintillation Model (GISM) was used to compute amplitude scintillation parameter for each GPS satellite visible from Melaka, Malaysia (Latitude 20 14’ N, Longitude 1020 16’ E) as its location has strong equatorial scintillation behavior. The output data from GISM was then used to calculate the positioning error where it is depends on the Dilution of Precision (DOP) and User Equivalent Range Error (UERE). There are two schemes that were used. First, the positioning error was calculated for all the visible satellites with better DOP but worse UERE due to scintillation event. Secondly, the positioning error was calculated for those satellites that have amplitude scintillation index, S4 < 0.7 which leads to worse DOP with better UERE. Comparison of results from the both schemes was then made

Solar irradiance forecasting for Malaysia using multiple regression and artificial neural network

The installed capacity of solar photovoltaic (PV) globally continues to rise. In Malaysia, the monthly average daily solar radiation is 4,000-5,000 Wh/m², with the average daily sunshine duration ranging from 4 to 8 h. However, the output of solar energy is related to solar irradiance, which lacks stability due to weather variation. Therefore, solar irradiance forecasting has become an important resource for network grid operators to control the output of solar PV energy. Weather forecasting data, such as temperature, dew point, humidity, pressure and wind speed, are widely available from local meteorological organisations. However, solar irradiance forecasting data is often unavailable. In this paper, multiple regression (MR) and artificial neural network (ANN) models are used to forecast solar irradiance using weather forecasting data. The correlation of each weather parameter with solar irradiance is investigated. It is evident that the ANN model is able to improve the accuracy in terms of root mean square error (RMSE) by 18.42% of its as compared to the MR mode

Some effects of earthquakes at North Sumatra to the total electron content in the Ionosphere

Total Electron Content (TEC) is an important ionospheric and space weather param- eter used for characterizing the state and dynamics of plasma in the ionosphere. As a result, this study was carried out to examine the possible relationship between the variations of the TEC in the ionosphere and the earthquakes and to identify the ef- fects of earthquakes to the TEC in the ionosphere. The analysis of ionospheric TEC variations were made using the Global Positioning System (GPS) station installed at Wireless and Radio Science Centre (WARAS), Kolej Universiti Teknologi Tun Hus- sein Onn (KUiTTHO), Johor (Latitude 1 ̊52 ́ N, longitude 103 ̊48 ́ E). Five cases of strong earthquakes at Indonesia in 2005 with M > 6.0 were selected as case studies. The TEC variations analysis of the GPS TEC collected by the GPS receiver in the year of 2005 were made to identify any TEC variations associated with earthquakes. Pronounced TEC variations around the time of earthquakes were analyzed with re- spect to the TEC variations during non-earthquake period. From the analysis, it was found that there appears to be rapid changes in TEC within 0 to 6 days before the earthquakes. Besides that, the TEC variations for all the cases show that the TEC gradually recovered to normal within 1 to 3 days after earthquakes. As a conclusion, strong earthquakes are reported to have caused disturbances in the ionosphere that can be measured with GPS as short-period changes in the TEC. The ionospheric TEC variations with average ∆ TEC = 10 TECU can be considered as a possible earthquake precursory

Bandwidth Widening Strategies for Piezoelectric Based Energy Harvesting from Ambient Vibration Sources

Due to the fact that the ambient vibration sources are random and unpredictable, therefore a vibration based energy harvesting device is desirable to be able to operate at wider bandwidth in an envelop of frequency range to generate maximum electrical output. In this paper, various ambient vibration from household appliances, machineries, vehicle and moving vehicle were measured and investigated. The second part of the paper will discuss the strategies to harvest these ambient vibration sources. An array of piezoelectric multi-cantilever is proposed to address the issue of single piezoelectric cantilever with high Q-factor. Two configurations of multi-cantilever were fabricated in a form that elevated from the substrate as freestanding structures. One with six cantilevers of constant width but different lengths and another with five cantilevers of constant length but different widths. The measurement and experimental results show a frequency band of 200 Hz to 300 Hz as a common bandwith between the vibration sources and the capability of miniature piezoelectric energy harvester in harvesting maximum electrical energy

On determining spectral parameters, tracking jitter, and GPS positioning improvement by scintillation mitigation

A method of determining spectral parameters p (slope of the phase PSD) and T (phase PSD at 1 Hz) and hence tracking error variance in a GPS receiver PLL from just amplitude and phase scintillation indices and an estimated value of the Fresnel frequency has been previously presented. Here this method is validated using 50 Hz GPS phase and amplitude data from high latitude receivers in northern Norway and Svalbard. This has been done both using (1) a Fresnel frequency estimated using the amplitude PSD (in order to check the accuracy of the method) and (2) a constant assumed value of Fresnel frequency for the data set, convenient for the situation when contemporaneous phase PSDs are not available. Both of the spectral parameters ( p, T ) calculated using this method are in quite good agreement with those obtained by direct measurements of the phase spectrum as are tracking jitter variances determined for GPS receiver PLLs using these values. For the Svalbard data set, a significant difference in the scintillation level observed on the paths from different satellites received simultaneously was noted. Then, it is shown that the accuracy of relative GPS positioning can be improved by use of the tracking jitter variance in weighting the measurements from each satellite used in the positioning estimation. This has significant advantages for scintillation mitigation, particularly since the method can be accomplished utilizing only time domain measurements thus obviating the need for the phase PSDs in order to extract the spectral parameters required for tracking jitter determination

Penentuan Gangguan Ionosfera Bergerak Menggunakan Data GPS

This study focuses on the determination of ionospheric disturbances over Malaysia using GPS (Global Positioning System) signals in order to have a better understanding of radio wave propagation. This is done by identifying the presence of Travelling Ionospheric Disturbance (TID) using GPS data. TID is one of the disturbances occuring in the ionosphere that is caused by solar activities. The important parameter taken into account is the Total Electron Content (TEC). The value of the rate of change of TEC, ΔTEC, is taken within a period of 15 minutes in order to detect the occurrences of TID. The data is taken from a GPS receiver stationed at the WARAS Center KUiTHHO, in Parit Raja, Batu Pahat (1°52’N, 103°06’E). The value of ΔTEC is compared based on the largest daily geomagnetic index, Kp index for 3 different days. Geomagnetic storms affect the ionospheric and the layer that is of interest is the F–layer of ionosphere. Results show that there is an occurrence of TID above the receiving station. Results also shows that there is a close correlation between the occurrence of TIDs and Kp values; a higher Kp index show an increase in the number of TIDs. However, more data need to be analysed in order to understand the variation of this disturbance to allow for space weather forecasting in the near future

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe