Impact of datum transformation on local variations of geometric geoid in Niger

Geodesy and Cartography

El Hassan El Brirchi¹  Driss El Azzab²  Salissou Ibrahim Yahaya³ 

[1] Department of Surveying, Institute of Technology (IUT) – University of Zinder – Mail box: 656, Zinder, Niger;Department of Mathematics, Computer Science and Geomatics – Hassaia School of Public Works – Mail box: 8108, km7 – El Jadida Road, Casablanca, Morocco;Geo-resources and Environment Laboratory – Faculty of Science and Technology – Sidi Mohamed Ben Abdallah University – Mail box: 2202, Imouzzer Road, Fez, Morocco;

关键词: geodetic datum;    coordinates transformation;    Geoid;    GPS/Levelling;    EGM2008;    Niger;   

DOI  :  10.3846/20296991.2017.1412615

来源: DOAJ

【 摘 要 】

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.

【 授权许可】

Unknown