ASSESSING THE POSITIONAL ACCURACY OF RAW GNSS DATA FROM ANDROID DEVICES Hasan Abdulhussein Jaafar, Jareer Mohammed Kufa Journal of Engineering, 2024 Smartphone devices have become the focus of attention of scholars dealing with GNSS measurements since May 2016 when Google stated using Android operating system version N that can access GNSS raw data. This opened the research door wide to process this data and analyse different issues in positioning by smartphones. Our study contributes to the assessment of GNSS data accuracy by evaluating various Android Application Programs (APPS) using Samsung Galaxy S9PLUS smartphone. While previous research has explored this topic, our study distinguishes itself through a comprehensive comparison of three APPS and two positioning techniques. By highlighting performance variations and considering multiple constellations, we provide valuable insights for smartphone GNSS users. Three different Apps were utilised: G-RitZ Logger, GnssLogger, and rinex ON. In addition, two GNSS positioning techniques were used for assessment: Post Processing Static (PPS) and Precise Point Positioning (PPP). The results revealed that GnssLogger obtain consistent readings in different scenarios. Therefore, GnssLogger is considered as the best logging GNSS data by smartphones. Moreover, accuracy is also discussed based on different constellations: GPS, GLONASS, and GALILEO. As expected, GPS results are the best compared to other constellations owing to availability and tracking priority for smartphone software. The best results obtained from GnssLogger with PPS technique and GPS system which has given RMS as 0.034 m, 0.171 m, and 0.383 m for E-W, N-S, and U-D axes respectively.
Adaptive neuro fuzzy inference system for predicting sub-daily Zenith Wet Delay Jareer Mohammed Geodesy and Geodynamics, 2022 In recent years, the focus of tropospheric studies has evolved to GNSS meteorology and weather forecasting. The Zenith Wet Delay (ZWD), which might be assembled to the Integrated Water Vapour (IWV), is an essential component of the tropospheric delay. Acquiring predicted the ZWD with the required level of accuracy is crucial for weather forecasting. The scope of this study is to use the adaptive neural fuzzy inference system (ANFIS) to predict the ZWD for the following six-hour epoch based exclusively on the present the ZWD value. It was developed and verified using 505 geographically and internationally distributed stations which were used for training and testing from 2008 to 2019. It was assessed based on two criteria. First, the correlation coefficient (R) values were found to be more than 0.8 in 98% of the stations, including those with highest and lowest latitudes, and the remaining 2% of stations located in coastal areas. Second, the Root Mean Square Error (RMSE) values of the differences between the predicted and the actual ZWD were considered to be the more important finding of the study. That is, 99.21% of the 505 stations had the RMSE values equal to or less than 3 cm, with only 4 stations having the RMSE values higher (0.2 mm) than 3 cm. Since the results of this study achieved the required degree of accuracy from the predicted ZWD to be utilized in weather forecasting, they may also be beneficial for GNSS meteorology.
Alternative Strategy for Estimating Zenith Tropospheric Delay from Precise Point Positioning Jareer Mohammed, Richard M. Bingley, Terry Moore, Chris Hill 2020 IEEE Ion Position Location and Navigation Symposium PLANS 2020, 2020 This This study considered zenith total delay (ZTD) estimation from precise point positioning (PPP) based on GPS only (PPP GPS), GLONASS only (PPP GLO), and GPS+GLONASS (PPP GPS+GLO) using both a conventional strategy when applying a model for the hydrostatic component with an estimation of the wet component and an alternative strategy. The proposed alternative strategy is to estimate both the hydrostatic and the wet components of the tropospheric delay using different process noises with different mapping functions for both components in an extended Kalman filter (EKF). It was found that the receiver clock offsets and the estimated ambiguities would absorb some errors in the ZTD when using the conventional strategy. The RMS values of the differences between the double differenced (DD) ZTD and the PPP ZTD, using the alternative strategy, were 6.5, 7.3, and 6.7 mm for GPS, GLO, and GPS+GLO, respectively. The results were validated over one continuous week and then over one year. Validation was also performed through comparison with the IGS final ZTD estimates values, for 12 weeks, with an overall RMS of 5.9 mm and against IGS real-time orbit and clock products with an overall RMS of 8.1 mm. Furthermore, the alternative strategy also provided significant improvements in the 5 cm convergence time in the vertical coordinate component of the float ambiguity solutions to be on average, 51, 36 and 27 minutes for PPP GPS, PPP GLO and PPP GPS+GLO solutions respectively.
Digital maps of mechanical geotechnical parameters using GIS Asad H. Aldefae, Jareer Mohammed, Hiba D. Saleem Cogent Engineering, 2020 Geographical Information System (GIS) is a powerful tool for representing huge data and producing an actual visualization of subsurface information and parameters in the form of 3D scenes that can be used by the geotechnical engineers in the design of footing and foundation. This paper focuses on producing digital geotechnical maps for the main geotechnical parameters that can be used in the preliminary design stage. Considerable data of 164 borehole logs presenting a 17,000 km2 (i.e. Wasit province, south of Baghdad, Iraq) are collected, analyzed, tabulated in an excel sheet, and used as input data to create the digital maps. The studied parameters are bearing capacity, shear strength, coefficient of consolidation, compressibility parameters, and groundwater levels. The results show that the GIS technique is a great tool to visualize the geotechnical parameters that can be easily used directly in the assessment of the site investigation reports and even in the foundation design. The digital values of the bearing capacities, shear strength, and compressibility parameters are clearly visualized and accurately replicate the soil layers of the study area. However, other geotechnical parameters are needed to further consider it in more digital maps.
An assessment of the precise products on static precise point positioning using multi-constellation GNSS Jareer Mohammed, Terry Moore, Chris Hill, Richard M. Bingley 2018 IEEE Ion Position Location and Navigation Symposium PLANS 2018 Proceedings, 2018 Precise point positioning (PPP) is highly dependent on the precise ephemerides and satellite clock products that are used. Different ephemeris and clock products are available from a variety of different organizations. The aim of this paper is to assess the achievable static positioning accuracy and precision when using different precise ephemerides from three analysis centres Natural Resources Canada (EMX), European Space Agency (ESA) and GeoForschungsZentrum (GFZ), using GPS alone, GLONASS alone, and GPS and GLONASS combined. It will be shown in this paper that the precise products are significantly affected by the time-base of the reference stations, and that this is propagated through to all the estimated satellite clocks. In order to overcome the combined biases in the estimated satellite clock, in the PPP processing, these clocks errors need to be handled with an appropriate variation in the estimated receiver clock. It will also be shown that the precise coordinates of the satellites differ between the analysis centres, and this affects the PPP position estimation at the millimetre level. However, all those products will be shown to result in the same level of precision for all coordinate components and are equivalent to the horizontal precision from a Global Double Difference (GDD) solution. For the horizontal coordinate component, the level of agreement between the PPP solutions, and with the GDD solution, is at the millimetre level. There is a notable, but small, bias in the north coordinate components of the PPP solutions, from the corresponding north component of the GDD solutions. It is shown that this difference is due to the different strategy adopted for the GDD and PPP solutions, with PPP being more affected by the changing satellite systems. The precision of the heights of the receiver sites will be shown to be almost the same across all the PPP scenarios, with all three products. Finally, it will be concluded that accuracy of the height component is system dependent and is related to the behaviour of antenna phase centre with the different constellation type.
ASSESSING THE POSITIONAL ACCURACY OF RAW GNSS DATA FROM ANDROID DEVICES. HA Jaafar, J Mohammed Kufa Journal of Engineering 15 (3) , 2024 2024 Citations: 1
Adaptive neuro fuzzy inference system for predicting sub-daily Zenith Wet Delay J Mohammed Geodesy and Geodynamics 13 (4), 352-362 , 2022 2022 Citations: 13
Artificial neural network for predicting global sub-daily tropospheric wet delay J Mohammed Journal of Atmospheric and Solar-Terrestrial Physics 217 , 2021 2021 Citations: 16
A spatial and temporal comparison of Five Total Electron Content providers J Mohammed IOP Conference Series Materials Science and Engineering 1058 (1) , 2021 2021 Citations: 1
Digital maps of mechanical geotechnical parameters using GIS HDS Asad H. Aldefae, Jareer Mohammed Civil and Environmental Engineering 7 (1), 1779563 , 2020 2020 Citations: 28
Alternative Strategy for Estimating Zenith Tropospheric Delay from Precise Point Positioning RMB Jareer Mohammed, Terry Moore, Chris Hill 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS), 247-258 , 2020 2020 Citations: 11
An assessment of the precise products on static Precise Point Positioning using Multi-Constellation GNSS J Mohammed, T Moore, C Hill, RM Bingley IEEE/ION PLANS 2018, 23-26 Apr 2018, Monterey, USA , 2018 2018 Citations: 5
Precise Point Positioning (PPP): GPS vs. GLONASS and GPS+ GLONASS with an alternative strategy for tropospheric Zenith Total Delay (ZTD) estimation JJ Mohammed University of Nottingham , 2017 2017 Citations: 2
An assessment of static precise point positioning using GPS only, GLONASS only, and GPS plus GLONASS J Mohammed, T Moore, C Hill, RM Bingley, DN Hansen Measurement 88, 121-130 , 2016 2016 Citations: 40
MOST CITED SCHOLAR PUBLICATIONS
An assessment of static precise point positioning using GPS only, GLONASS only, and GPS plus GLONASS J Mohammed, T Moore, C Hill, RM Bingley, DN Hansen Measurement 88, 121-130 , 2016 2016 Citations: 40
Digital maps of mechanical geotechnical parameters using GIS HDS Asad H. Aldefae, Jareer Mohammed Civil and Environmental Engineering 7 (1), 1779563 , 2020 2020 Citations: 28
Artificial neural network for predicting global sub-daily tropospheric wet delay J Mohammed Journal of Atmospheric and Solar-Terrestrial Physics 217 , 2021 2021 Citations: 16
Adaptive neuro fuzzy inference system for predicting sub-daily Zenith Wet Delay J Mohammed Geodesy and Geodynamics 13 (4), 352-362 , 2022 2022 Citations: 13
Alternative Strategy for Estimating Zenith Tropospheric Delay from Precise Point Positioning RMB Jareer Mohammed, Terry Moore, Chris Hill 2020 IEEE/ION Position, Location and Navigation Symposium (PLANS), 247-258 , 2020 2020 Citations: 11
An assessment of the precise products on static Precise Point Positioning using Multi-Constellation GNSS J Mohammed, T Moore, C Hill, RM Bingley IEEE/ION PLANS 2018, 23-26 Apr 2018, Monterey, USA , 2018 2018 Citations: 5
Precise Point Positioning (PPP): GPS vs. GLONASS and GPS+ GLONASS with an alternative strategy for tropospheric Zenith Total Delay (ZTD) estimation JJ Mohammed University of Nottingham , 2017 2017 Citations: 2
ASSESSING THE POSITIONAL ACCURACY OF RAW GNSS DATA FROM ANDROID DEVICES. HA Jaafar, J Mohammed Kufa Journal of Engineering 15 (3) , 2024 2024 Citations: 1
A spatial and temporal comparison of Five Total Electron Content providers J Mohammed IOP Conference Series Materials Science and Engineering 1058 (1) , 2021 2021 Citations: 1
