http://orcid.org/0000-0002-7820-5845
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Abstract
In this study, we have conducted an investigation on the impact of the coordinates’ transformation on local variations of geometric geoid. The study area is limited by 1°43′12″ to 4°00′37″ East and 13°01′57″ to 14°31′20″ North in the southwest of the Niger Republic. We used 39 network GPS/levelling points established by the Japan International Cooperation Agency (JICA) and the National Geographic Institute of Niger (IGNN), including the DOPPLER point ANG302/no.65. Using other coordinates of point no. 65 provided by IGNN, we transformed the points into WGS84 and computed a new geometric geoid model. The comparison of the new model with EGM2008 geoid up to d/o 2160 gives the STD of 15 cm and the RMS of 16cm. Local variations of the geometric geoids, were compared to that of EGM2008 geoid. The comparison through basic statistics, trend lines and 3D overlaps, showed a similar trend between the geometric geoid from the transformed coordinates and that of EGM2008. On the contrary, the JICA-IGNN geometric geoid generated an opposite and exaggerated trend. The Jarque-Bera test confirms that the three samples follow a normal distribution at the significance level α = 5%. The equality of variances between EGM2008 and JICA-IGNN geoids has been rejected by the Fisher’s F-Test/two-tailed at α = 10%. However the test confirms the variances equality between EGM2008 and the transformed geometric geoid at α = 5% and α = 10%. The two-tailed Student’s T-Test at α = 5% also confirms the equality of means between EGM2008 geoid and transformed geometric geoid samples.
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Notes on contributors
Salissou Ibrahim Yahaya
Salissou IBRAHIM YAHAYA received the Engineering degree in Geomatics in 2009 from Hassania School of Public Works (EHTP) - Casablanca - Morocco. He had worked in many projects through the Niger Republic, particularly Mining, Civil Engineering and Urban Planning. He has taught at the Department of Geosciences, College of Mining, industry and Geology (EMIG) in Niamey - Niger. He joined the Institute of Technology of the University of Zinder, Niger in October 2012 as a permanent technologist teacher. Since December 2014, he is PhD student at the Georessources and Environment Laboratory. His research interests are Physical Geodesy, Surveying, GNSS, Remote Sensing and GIS.
El Hassan El Brirchi
El Hassan EL BRIRCHI obtained the Engineering degree in GIS from Hassania School of Public Works (EHTP) - Casablanca - Morocco, the Master degree in Surveying from National School of Geographic Sciences - Paris - France and the PhD degree in Geological Engineering from the Faculty of Sciences and Techniques - Fez - Morocco, respectively in 2001, 2003 and 2013. He is an Engineer since 2003 and an Associate Professor since 2013 at the Department of Mathematics, Computer Science and Geomatics, Hassania School of Public Works. His research interest is about Physical Geodesy, GPS, GIS Networks and Urban Transport planning.
Driss El Azzab
Driss EL AZZAB obtained the Master degree in Internal Geophysics from Earth Physics Institute (Paris VI University) - Paris, the PhD degree in Geodynamics and Physics of the Earth from Orsay Univesity and High Normal School (ENS) - Paris and the PhD degree in Geophysics from Sidi Mohamed Ben Abdellah University - Fes, respectively in 1989, 1993 and 1999. He is a Professor at the Faculty of Sciences and Techniques, Fez - Morocco, Morocco. His research interests are Paleomagnetism, Aeromagnetism, Electrical Tomography, GeoRadar and Gravimetry.