Joseph Dodo - Academia.edu (original) (raw)

Papers by Joseph Dodo

Research paper thumbnail of A Proposal for the Extension and Institutional Framework of European Geostationary Navigation Overlay Service (EGNOS) in the implementation of Global Navigation Satellite System (GNSS) in Africa

FUTY Journal of the Environment, 2011

Research paper thumbnail of Estimating Station Specific Zenith Tropospheric Delay in a Local GPS Network from Observed Surface Meteorology

Journal of geosciences and geomatics, Apr 16, 2021

Research paper thumbnail of ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results

Journal of …, 2011

... 978 ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results Dod... more ... 978 ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results Dodo, JD; Yakubu, TA; Usifoh, ES, and Bojude, A ... Twelve realizations of the ITRS were set up from 1988. The latest is the ITRF2008. ...

Research paper thumbnail of Determination of a GNSS-Based Velocity Field of the African Continent

International Association of Geodesy Symposia

GNSS-based velocity fields are a key tool to assess the boundaries around major deforming areas, ... more GNSS-based velocity fields are a key tool to assess the boundaries around major deforming areas, to explain the main patterns of surface motion and deformation, to analytically review existing kinematics models and finally, to study the underlying tectonic activities. Determination of a velocity field for Africa is of great importance in the determination of the African Reference Frame; this is essential for better understanding the African plate tectonics. Therefore, this study focusses on the determination of the African velocity fields using continuously operated GNSS stations. We processed and analyzed 11 years of data obtained from a total number of 145 GNSS site using GFZ’s EPOS.P8 software. The result shows that Africa moves in the North-East direction. The station coordinates derived with PPP show averaged RMS values of 2.9 mm, 9.9 mm and 8.5 mm for the north, east and up components with respect to the estimated trajectory models. Horizontal velocities at sites located on st...

Research paper thumbnail of Assessment of long-term impact of solar activity on the ionosphere over an African equatorial GNSS station

Earth Science Informatics

Research paper thumbnail of A methodology for estimating accurate velocity field of NigNET based on new ITRF realization

Contributions to Geophysics and Geodesy

This contribution presents a new velocity field describing the crustal motion of Nigeria from mor... more This contribution presents a new velocity field describing the crustal motion of Nigeria from more than 5years continuous GNSS data at 8 of 14 permanent stations distributed across the country. GAMIT/GLOBK GNSS processing software was used for processing. The horizontal velocity field of NigNET stations which showed a North-East trend and the selected IGS stations were obtained from cleaned position time series of daily GNSS solutions. The velocity describe the horizontal and vertical motion the selected 8 GNSS stations assuming Flicker +White noise model, which optimally describes the geophysical error source of the adopted GNSS stations. Bland and Altman statistical method shows that residual velocity solutions of our study and others (in ITRF2008) and also MORVEL plate motion model are in agreement.

Research paper thumbnail of Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (O... more The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (OSGoF) set up surveying infrastructure throughout the country known as the NIGerian Reference GNSS NETwork (NIGNET). The NIGNET is a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) set up at different locations in Nigeria for surveying and mapping. They are satellite tracking stations operating 24 hours a day providing positional solutions. As signals from the satellite pass through the different layers of the atmosphere (ionosphere and troposphere), they are refracted thus, causing delay on the arrival of the signal, which in-turns affect positioning in the horizontal and height component. The most dominant spatially correlated bias is the tropospheric effect on the GNSS satellite signals. Several global tropospheric delay models are in use by different countries to mitigate the biases cause by the troposphere. This study therefore ai...

Research paper thumbnail of GNSS Sky Visibility Planning and Dilution of Precision Analysis for EOS Ground Station Selection for Nigeria Space Programme

Journal of Geospatial Science and Technology, 2014

The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nige... more The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nigeria and other parts of the globe, similar to the Indian Remote Sensing (IRS) model will enhance global telecommand, precise EOS tracking, data transmission, and distribution of NigeriaSat data, which will enhance global-scale data awareness, usage and higher financial returns for Nigeria. This study, therefore, attempts the application of Global Navigation Satellite System (GNSS) sky visibility planning and dilution of precision analysis technique to select the optimal location for EOS ground station(s) in Nigeria. The Nigerian Geodetic Network (NigNet) GNSS Continuously Operating Reference Stations (CORS) RINEX data of February 2012 and Trimble Total Control (TTC) software were used for the determinations of the baselines and positions of the 11 available CORS. The technique of GNSS sky visibility planning and dilution of precision (DOP) was adopted because signals from satellites behav...

Research paper thumbnail of Regional ionospheric total electron content over Africa from ground-based GNSS observations

Due to the wide use of GNSS receivers both on satellites at low earth orbit and on the ground, co... more Due to the wide use of GNSS receivers both on satellites at low earth orbit and on the ground, continuous and long-time ionospheric data with increasing accuracy have been obtained and used to study variations in the Earth’s ionosphere. Daily data from 2010.001 to 2017.365 sampled at 30 seconds from 104 African Geodetic Reference Frame (AFREF) dual-frequency GNSS Continuously Operating Reference Stations receivers distributed across Africa, were used in this study. Single Layer Model which assumes that all free electrons are concentrated in a shell of infinitesimal thickness, provides determining ionospheric total electron content value. In this study, the SLM model was used to derive total electron content values. TEC values obtained from the AFREF GNSS CORS measurements were compared with the TEC values from the global ionosphere maps provided by the Centre for Orbit Determination in Europe (CODE). The comparison was achieved by means of time series and wavelet analyses, and also ...

Research paper thumbnail of Strain rate field on the Nigeria lithosphere derived from GNSS velocity

Research paper thumbnail of Regional TEC modelling over Africa using deep structured supervised neural network

Geodesy and Geodynamics, 2020

Abstract A deep structured supervised neural network (NN) model has been developed for modelling ... more Abstract A deep structured supervised neural network (NN) model has been developed for modelling of ionospheric vertical total electron content (VTEC) using observations from over 100 Global Navigation Satellite System continuously operating reference stations (GNSS CORS) across Africa. The study covers all available data during low, moderate and declining phases of solar cycle 24, from 2009 to 2017. Optimal network parameters combination for the regional model includes a combination of spatio-temporal parameters (latitude, longitude, year, day of the year, hour), geomagnetic and solar parameters (F10.7, AE, Dst indices), hidden layer of 20 neurons and a feedforward network with Levenberg–Marquardt back-propagation algorithm. The validation and the test curves do not indicate overfitting and the performance curves of the training, validation and test data show a very similar trend. Thus, the performance of the optimal network with learning data is in sync with the data not assimilated in the learning process. The African Regional Ionospheric Tec Model (ARITM) developed in this study reproduces the known spatiotemporal features of the equatorial and low-latitudes ionosphere quite well. The ARITM performs well to a considerably high degree of precision within the Africa region by comparison with the global ionospheric maps (GIMs) and the Formosa Satellite-3 Constellation Observing System for Meteorology, Ionosphere & Climate (FORMOSAT-3/COSMIC) observations. The results suggest that the developed model can efficiently be adopted as a substitute for single station ionospheric model for any single GNSS station within Africa, avoiding the need for developing independent multiple single station ionospheric models for each of the existing and future GNSS stations within the African region.

Research paper thumbnail of Investigation on the Impact of Tropospheric Delay on GPS Height Variation near the Equator

African Journal of Information & Communication Technology

One of the major problems currently facing satellite-based positioning is the atmospheric refract... more One of the major problems currently facing satellite-based positioning is the atmospheric refraction of the GPS signal caused by the troposphere. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions. This affects the GPS signal due to the variability of the refractive index, which in turn affects the positional accuracy, especially in the height components. This paper presents a study conducted in the Southern Peninsular Malaysia located at the equatorial region, to investigate the impact of tropospheric delay on GPS height variation. Four campaigns were launched with each campaign lasting for three days. The Malaysian real-time kinematic GPS network (MyRTKnet) reference stations in Johor Bahru were used. GPS RINEX data from these stations were integrated with ground meteorological data observed concurrently from a GPS station located at the Universiti Teknologi Malaysia (UTM), at varying antenna heights for each session of obser...

Research paper thumbnail of Ojigi et al: Nigerian Association of Geodesy Application of GNSS CORS in Earth Observation Satellites Ground Station Selection and Control for Nigeria Space Programme

In order to maximize global scientific collaboration on the utilization of data products from Nig... more In order to maximize global scientific collaboration on the utilization of data products from NigeriaSat payloads, there may be need to have additional ground stations in Nigeria, across Africa, Asia and Europe, etc. Ground station network is the means by which satellites stay in contact with the Earth, through which data reception and satellite controls are realized. The Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) Infrastructure in Nigeria and IGS around are relevant in the site selection, data facility evaluation and EOS tracking/control of the Nigeria satellites payloads. The study used the GNSS CORS data of February 2010 and the Two Line Element (TLE) set of NigeriaSat-1 (N-1) Orbit to make sky visibility analysis for EOS ground Station selection in Nigeria and the trend analysis of N-1 orbital behavior for a period of seven years (1 st January 2004 – 1 st January 2011). The optimized DOP values of majority of the eleven stations wer...

Research paper thumbnail of © Science and Education Publishing DOI:10.12691/jgg-3-4-1 Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

Research paper thumbnail of Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (O... more The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (OSGoF) set up surveying infrastructure throughout the country known as the NIGerian Reference GNSS NETwork (NIGNET). The NIGNET is a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) set up at different locations in Nigeria for surveying and mapping. They are satellite tracking stations operating 24 hours a day providing positional solutions. As signals from the satellite pass through the different layers of the atmosphere (ionosphere and troposphere), they are refracted thus, causing delay on the arrival of the signal, which in-turns affect positioning in the horizontal and height component. The most dominant spatially correlated bias is the tropospheric effect on the GNSS satellite signals. Several global tropospheric delay models are in use by different countries to mitigate the biases cause by the troposphere. This study therefore ai...

Research paper thumbnail of Regional TEC modelling over Africa using deep structured supervised neural network

Geodesy and Geodynamics, 2020

A deep structured supervised neural network (NN) model has been developed for modelling of ionosp... more A deep structured supervised neural network (NN) model has been developed for modelling of ionospheric vertical total electron content (VTEC) using observations from over 100 Global Navigation Satellite System continuously operating reference stations (GNSS CORS) across Africa. The study covers all available data during low, moderate and declining phases of solar cycle 24, from 2009 to 2017. Optimal network parameters combination for the regional model includes a combination of spatio-temporal parameters (latitude, longitude, year, day of the year, hour), geomagnetic and solar parameters (F10.7, AE, Dst indices), hidden layer of 20 neurons and a feedforward network with Levenberg–Marquardt back-propagation algorithm. The validation and the test curves do not indicate overfitting and the performance curves of the training, validation and test data show a very similar trend. Thus, the performance of the optimal network with learning data is in sync with the data not assimilated in the...

Research paper thumbnail of Meteorological parameter modelling in a local GPS network in Southern Peninsular Malaysia

All strongly region GPS signals, which in turns affect positioning. This arises from th... more All strongly region GPS signals, which in turns affect positioning. This arises from the fact that, the country is characterised copious due to its high humidity, thus regarded as a ‘tropical rainforest’. This paper presents a study conducted in Southern Malaysia near the equator, to model two and half (21/2) years meteorological parameters; temperature, pressure and relative humidity from four weather stations network MetMOD nonparametric trend statistics used to analyse trends at each of the GPS network reference station. reveals that, temperature agrees with the observed data at an average mean difference of 0.1620C pressure at an average mean difference of about 0.179 hPa and RMSE of 0.251 hPa; while relative results show that; relative humidity showed most of the upward and downward trends, having more effects on stations with small ellipsoidal height; where...

Research paper thumbnail of Application of GNSS CORS in Earth Observation Satellites Ground Station Selection and Control for Nigeria Space Programme

In order to maximize global scientific collaboration on the utilization of data products from Nig... more In order to maximize global scientific collaboration on the utilization of data products from NigeriaSat payloads, there may be need to have additional ground stations in Nigeria, across Africa, Asia and Europe, etc. Ground station network is the means by which satellites stay in contact with the Earth, through which data reception and satellite controls are realized. The Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) Infrastructure in Nigeria and IGS around are relevant in the site selection, data facility evaluation and EOS tracking/control of the Nigeria satellites payloads. The study used the GNSS CORS data of February 2010 and the Two Line Element (TLE) set of NigeriaSat-1 (N-1) Orbit to make sky visibility analysis for EOS ground Station selection in Nigeria and the trend analysis of N-1 orbital behavior for a period of seven years (1 st January 2004 – 1 st January 2011). The optimized DOP values of majority of the eleven stations wer...

Research paper thumbnail of The Effect of Tropospheric Delay on GPS Height Differences Along the Equator

The fundamental issue in GPS positioning is the ability to mitigate all the potential errors and ... more The fundamental issue in GPS positioning is the ability to mitigate all the potential errors and biases in the system. The atmosphere related errors of ionosphere and troposphere constitute one of these potential errors. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions. This significantly affects the GPS signal due to the variability of the refractive index, which in turn affects the accuracy of GPS positioning, especially in the height components. This paper presents a study conducted in Malaysia located at the equatorial region, to investigate the impact of tropospheric delay on GPS height variation. Five GPS reference stations forming part of the Malaysian real-time kinematic GPS network (MyRTKnet) in johor were used. RINEX data from these stations were integrated with GPS and ground meteorological data observed from a GPS station located at the Universiti Teknologi Malaysia (UTM), at varying antenna heights for each sessi...

Research paper thumbnail of Evaluation of Five Tropospheric Delay Models on Global Navigation Satellite System Measurements in Southern Nigeria

Throughout Nigeria, the structure and facilities needed for the operation of a Global Navigation ... more Throughout Nigeria, the structure and facilities needed for the operation of a Global Navigation Satellite System (GNSS) based Continuously Operating Reference Stations (CORS) has been set up at different locations in the country generally known as NIGerian Reference GNSS NETwork (NIGNET) for surveying and mapping. Different researchers have conducted investigations into the effect of the troposphere over the NIGNET. This study aims at comparing analytically the effect of five different a priori tropospheric models on GNSS signals in Southern Nigeria with a view to obtaining the best-fit model. The objectives include evaluation of the global tropospheric models in the baseline and position domain; and determining the best model for southern Nigeria. Observational data used were obtained from Office of Surveyor General of Nigerian Mapping Agency (OSGoF). GPS data were obtained from October 2010, to April 2011. Six processing strategies were employed these include; application of no m...

Research paper thumbnail of A Proposal for the Extension and Institutional Framework of European Geostationary Navigation Overlay Service (EGNOS) in the implementation of Global Navigation Satellite System (GNSS) in Africa

FUTY Journal of the Environment, 2011

Research paper thumbnail of Estimating Station Specific Zenith Tropospheric Delay in a Local GPS Network from Observed Surface Meteorology

Journal of geosciences and geomatics, Apr 16, 2021

Research paper thumbnail of ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results

Journal of …, 2011

... 978 ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results Dod... more ... 978 ITRF 2008 Realization of the Nigerian Geocentric Datum (GDN2012): Preliminary Results Dodo, JD; Yakubu, TA; Usifoh, ES, and Bojude, A ... Twelve realizations of the ITRS were set up from 1988. The latest is the ITRF2008. ...

Research paper thumbnail of Determination of a GNSS-Based Velocity Field of the African Continent

International Association of Geodesy Symposia

GNSS-based velocity fields are a key tool to assess the boundaries around major deforming areas, ... more GNSS-based velocity fields are a key tool to assess the boundaries around major deforming areas, to explain the main patterns of surface motion and deformation, to analytically review existing kinematics models and finally, to study the underlying tectonic activities. Determination of a velocity field for Africa is of great importance in the determination of the African Reference Frame; this is essential for better understanding the African plate tectonics. Therefore, this study focusses on the determination of the African velocity fields using continuously operated GNSS stations. We processed and analyzed 11 years of data obtained from a total number of 145 GNSS site using GFZ’s EPOS.P8 software. The result shows that Africa moves in the North-East direction. The station coordinates derived with PPP show averaged RMS values of 2.9 mm, 9.9 mm and 8.5 mm for the north, east and up components with respect to the estimated trajectory models. Horizontal velocities at sites located on st...

Research paper thumbnail of Assessment of long-term impact of solar activity on the ionosphere over an African equatorial GNSS station

Earth Science Informatics

Research paper thumbnail of A methodology for estimating accurate velocity field of NigNET based on new ITRF realization

Contributions to Geophysics and Geodesy

This contribution presents a new velocity field describing the crustal motion of Nigeria from mor... more This contribution presents a new velocity field describing the crustal motion of Nigeria from more than 5years continuous GNSS data at 8 of 14 permanent stations distributed across the country. GAMIT/GLOBK GNSS processing software was used for processing. The horizontal velocity field of NigNET stations which showed a North-East trend and the selected IGS stations were obtained from cleaned position time series of daily GNSS solutions. The velocity describe the horizontal and vertical motion the selected 8 GNSS stations assuming Flicker +White noise model, which optimally describes the geophysical error source of the adopted GNSS stations. Bland and Altman statistical method shows that residual velocity solutions of our study and others (in ITRF2008) and also MORVEL plate motion model are in agreement.

Research paper thumbnail of Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (O... more The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (OSGoF) set up surveying infrastructure throughout the country known as the NIGerian Reference GNSS NETwork (NIGNET). The NIGNET is a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) set up at different locations in Nigeria for surveying and mapping. They are satellite tracking stations operating 24 hours a day providing positional solutions. As signals from the satellite pass through the different layers of the atmosphere (ionosphere and troposphere), they are refracted thus, causing delay on the arrival of the signal, which in-turns affect positioning in the horizontal and height component. The most dominant spatially correlated bias is the tropospheric effect on the GNSS satellite signals. Several global tropospheric delay models are in use by different countries to mitigate the biases cause by the troposphere. This study therefore ai...

Research paper thumbnail of GNSS Sky Visibility Planning and Dilution of Precision Analysis for EOS Ground Station Selection for Nigeria Space Programme

Journal of Geospatial Science and Technology, 2014

The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nige... more The establishment of Earth Observation Satellite (EOS) ground receiving stations in parts of Nigeria and other parts of the globe, similar to the Indian Remote Sensing (IRS) model will enhance global telecommand, precise EOS tracking, data transmission, and distribution of NigeriaSat data, which will enhance global-scale data awareness, usage and higher financial returns for Nigeria. This study, therefore, attempts the application of Global Navigation Satellite System (GNSS) sky visibility planning and dilution of precision analysis technique to select the optimal location for EOS ground station(s) in Nigeria. The Nigerian Geodetic Network (NigNet) GNSS Continuously Operating Reference Stations (CORS) RINEX data of February 2012 and Trimble Total Control (TTC) software were used for the determinations of the baselines and positions of the 11 available CORS. The technique of GNSS sky visibility planning and dilution of precision (DOP) was adopted because signals from satellites behav...

Research paper thumbnail of Regional ionospheric total electron content over Africa from ground-based GNSS observations

Due to the wide use of GNSS receivers both on satellites at low earth orbit and on the ground, co... more Due to the wide use of GNSS receivers both on satellites at low earth orbit and on the ground, continuous and long-time ionospheric data with increasing accuracy have been obtained and used to study variations in the Earth’s ionosphere. Daily data from 2010.001 to 2017.365 sampled at 30 seconds from 104 African Geodetic Reference Frame (AFREF) dual-frequency GNSS Continuously Operating Reference Stations receivers distributed across Africa, were used in this study. Single Layer Model which assumes that all free electrons are concentrated in a shell of infinitesimal thickness, provides determining ionospheric total electron content value. In this study, the SLM model was used to derive total electron content values. TEC values obtained from the AFREF GNSS CORS measurements were compared with the TEC values from the global ionosphere maps provided by the Centre for Orbit Determination in Europe (CODE). The comparison was achieved by means of time series and wavelet analyses, and also ...

Research paper thumbnail of Strain rate field on the Nigeria lithosphere derived from GNSS velocity

Research paper thumbnail of Regional TEC modelling over Africa using deep structured supervised neural network

Geodesy and Geodynamics, 2020

Abstract A deep structured supervised neural network (NN) model has been developed for modelling ... more Abstract A deep structured supervised neural network (NN) model has been developed for modelling of ionospheric vertical total electron content (VTEC) using observations from over 100 Global Navigation Satellite System continuously operating reference stations (GNSS CORS) across Africa. The study covers all available data during low, moderate and declining phases of solar cycle 24, from 2009 to 2017. Optimal network parameters combination for the regional model includes a combination of spatio-temporal parameters (latitude, longitude, year, day of the year, hour), geomagnetic and solar parameters (F10.7, AE, Dst indices), hidden layer of 20 neurons and a feedforward network with Levenberg–Marquardt back-propagation algorithm. The validation and the test curves do not indicate overfitting and the performance curves of the training, validation and test data show a very similar trend. Thus, the performance of the optimal network with learning data is in sync with the data not assimilated in the learning process. The African Regional Ionospheric Tec Model (ARITM) developed in this study reproduces the known spatiotemporal features of the equatorial and low-latitudes ionosphere quite well. The ARITM performs well to a considerably high degree of precision within the Africa region by comparison with the global ionospheric maps (GIMs) and the Formosa Satellite-3 Constellation Observing System for Meteorology, Ionosphere & Climate (FORMOSAT-3/COSMIC) observations. The results suggest that the developed model can efficiently be adopted as a substitute for single station ionospheric model for any single GNSS station within Africa, avoiding the need for developing independent multiple single station ionospheric models for each of the existing and future GNSS stations within the African region.

Research paper thumbnail of Investigation on the Impact of Tropospheric Delay on GPS Height Variation near the Equator

African Journal of Information & Communication Technology

One of the major problems currently facing satellite-based positioning is the atmospheric refract... more One of the major problems currently facing satellite-based positioning is the atmospheric refraction of the GPS signal caused by the troposphere. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions. This affects the GPS signal due to the variability of the refractive index, which in turn affects the positional accuracy, especially in the height components. This paper presents a study conducted in the Southern Peninsular Malaysia located at the equatorial region, to investigate the impact of tropospheric delay on GPS height variation. Four campaigns were launched with each campaign lasting for three days. The Malaysian real-time kinematic GPS network (MyRTKnet) reference stations in Johor Bahru were used. GPS RINEX data from these stations were integrated with ground meteorological data observed concurrently from a GPS station located at the Universiti Teknologi Malaysia (UTM), at varying antenna heights for each session of obser...

Research paper thumbnail of Ojigi et al: Nigerian Association of Geodesy Application of GNSS CORS in Earth Observation Satellites Ground Station Selection and Control for Nigeria Space Programme

In order to maximize global scientific collaboration on the utilization of data products from Nig... more In order to maximize global scientific collaboration on the utilization of data products from NigeriaSat payloads, there may be need to have additional ground stations in Nigeria, across Africa, Asia and Europe, etc. Ground station network is the means by which satellites stay in contact with the Earth, through which data reception and satellite controls are realized. The Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) Infrastructure in Nigeria and IGS around are relevant in the site selection, data facility evaluation and EOS tracking/control of the Nigeria satellites payloads. The study used the GNSS CORS data of February 2010 and the Two Line Element (TLE) set of NigeriaSat-1 (N-1) Orbit to make sky visibility analysis for EOS ground Station selection in Nigeria and the trend analysis of N-1 orbital behavior for a period of seven years (1 st January 2004 – 1 st January 2011). The optimized DOP values of majority of the eleven stations wer...

Research paper thumbnail of © Science and Education Publishing DOI:10.12691/jgg-3-4-1 Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

Research paper thumbnail of Determination of the best-fit Tropospheric Delay Model on the Nigerian Permanent GNSS Network

The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (O... more The Federal Government of Nigeria through the Office of the Surveyor General of the Federation (OSGoF) set up surveying infrastructure throughout the country known as the NIGerian Reference GNSS NETwork (NIGNET). The NIGNET is a network of Global Navigation Satellite System (GNSS) Continuously Operating Reference Stations (CORS) set up at different locations in Nigeria for surveying and mapping. They are satellite tracking stations operating 24 hours a day providing positional solutions. As signals from the satellite pass through the different layers of the atmosphere (ionosphere and troposphere), they are refracted thus, causing delay on the arrival of the signal, which in-turns affect positioning in the horizontal and height component. The most dominant spatially correlated bias is the tropospheric effect on the GNSS satellite signals. Several global tropospheric delay models are in use by different countries to mitigate the biases cause by the troposphere. This study therefore ai...

Research paper thumbnail of Regional TEC modelling over Africa using deep structured supervised neural network

Geodesy and Geodynamics, 2020

A deep structured supervised neural network (NN) model has been developed for modelling of ionosp... more A deep structured supervised neural network (NN) model has been developed for modelling of ionospheric vertical total electron content (VTEC) using observations from over 100 Global Navigation Satellite System continuously operating reference stations (GNSS CORS) across Africa. The study covers all available data during low, moderate and declining phases of solar cycle 24, from 2009 to 2017. Optimal network parameters combination for the regional model includes a combination of spatio-temporal parameters (latitude, longitude, year, day of the year, hour), geomagnetic and solar parameters (F10.7, AE, Dst indices), hidden layer of 20 neurons and a feedforward network with Levenberg–Marquardt back-propagation algorithm. The validation and the test curves do not indicate overfitting and the performance curves of the training, validation and test data show a very similar trend. Thus, the performance of the optimal network with learning data is in sync with the data not assimilated in the...

Research paper thumbnail of Meteorological parameter modelling in a local GPS network in Southern Peninsular Malaysia

All strongly region GPS signals, which in turns affect positioning. This arises from th... more All strongly region GPS signals, which in turns affect positioning. This arises from the fact that, the country is characterised copious due to its high humidity, thus regarded as a ‘tropical rainforest’. This paper presents a study conducted in Southern Malaysia near the equator, to model two and half (21/2) years meteorological parameters; temperature, pressure and relative humidity from four weather stations network MetMOD nonparametric trend statistics used to analyse trends at each of the GPS network reference station. reveals that, temperature agrees with the observed data at an average mean difference of 0.1620C pressure at an average mean difference of about 0.179 hPa and RMSE of 0.251 hPa; while relative results show that; relative humidity showed most of the upward and downward trends, having more effects on stations with small ellipsoidal height; where...

Research paper thumbnail of Application of GNSS CORS in Earth Observation Satellites Ground Station Selection and Control for Nigeria Space Programme

In order to maximize global scientific collaboration on the utilization of data products from Nig... more In order to maximize global scientific collaboration on the utilization of data products from NigeriaSat payloads, there may be need to have additional ground stations in Nigeria, across Africa, Asia and Europe, etc. Ground station network is the means by which satellites stay in contact with the Earth, through which data reception and satellite controls are realized. The Global Navigation Satellite System (GNSS) Continuously Operating Reference Station (CORS) Infrastructure in Nigeria and IGS around are relevant in the site selection, data facility evaluation and EOS tracking/control of the Nigeria satellites payloads. The study used the GNSS CORS data of February 2010 and the Two Line Element (TLE) set of NigeriaSat-1 (N-1) Orbit to make sky visibility analysis for EOS ground Station selection in Nigeria and the trend analysis of N-1 orbital behavior for a period of seven years (1 st January 2004 – 1 st January 2011). The optimized DOP values of majority of the eleven stations wer...

Research paper thumbnail of The Effect of Tropospheric Delay on GPS Height Differences Along the Equator

The fundamental issue in GPS positioning is the ability to mitigate all the potential errors and ... more The fundamental issue in GPS positioning is the ability to mitigate all the potential errors and biases in the system. The atmosphere related errors of ionosphere and troposphere constitute one of these potential errors. The tropospheric effect is much more pronounced at the equatorial region due to its hot and wet conditions. This significantly affects the GPS signal due to the variability of the refractive index, which in turn affects the accuracy of GPS positioning, especially in the height components. This paper presents a study conducted in Malaysia located at the equatorial region, to investigate the impact of tropospheric delay on GPS height variation. Five GPS reference stations forming part of the Malaysian real-time kinematic GPS network (MyRTKnet) in johor were used. RINEX data from these stations were integrated with GPS and ground meteorological data observed from a GPS station located at the Universiti Teknologi Malaysia (UTM), at varying antenna heights for each sessi...

Research paper thumbnail of Evaluation of Five Tropospheric Delay Models on Global Navigation Satellite System Measurements in Southern Nigeria

Throughout Nigeria, the structure and facilities needed for the operation of a Global Navigation ... more Throughout Nigeria, the structure and facilities needed for the operation of a Global Navigation Satellite System (GNSS) based Continuously Operating Reference Stations (CORS) has been set up at different locations in the country generally known as NIGerian Reference GNSS NETwork (NIGNET) for surveying and mapping. Different researchers have conducted investigations into the effect of the troposphere over the NIGNET. This study aims at comparing analytically the effect of five different a priori tropospheric models on GNSS signals in Southern Nigeria with a view to obtaining the best-fit model. The objectives include evaluation of the global tropospheric models in the baseline and position domain; and determining the best model for southern Nigeria. Observational data used were obtained from Office of Surveyor General of Nigerian Mapping Agency (OSGoF). GPS data were obtained from October 2010, to April 2011. Six processing strategies were employed these include; application of no m...