Computations of Geoid Undulation from Comparison of GNSS/Levelling with EGM 2008 for Geodetic App

What is it about?

Consistency is an important characteristic in height systems which the mean sea level (msl) surface cannot guarantee. Only a geoid surface can provide height consistency. The quality of geoid undulation (N) will obviously affect the resulting orthometric height (H) determined from GNSS. The geoid undulation may be global, regional or national and local. Online software CSRS-PPP was used for post processing rinex data. EGM2008 was computed from AllTrans EGM2008 geoid calculator while h was used to compute NGPS from the relationship N= h-H. H is the existing orthometric height. Twenty-four controls with FCT 260 P as base reference station were used for this study. The computed standard deviation of differences in NGPS− NEGM2008 (σ) is used as accuracy indicator and σ = 0.419m .The root mean square error (RMSE) is 0.934m. This indicates the quality and reliability of the geoid undulation from the EGM2008 model. Comparing the observed NGNSS and NEGM2008, the use of global models may not satisfy the accuracy level of orthometric height desired for local applications in the FCT, Abuja. GNSS (GPS) may be used along with local geoid model as a way to acquire acceptable orthometric height. The smaller the NGPS- NEGM2008 makes it better model. The range of 1.585m from (NGPS- NEGM2008) in this study is a strong indication that global models should be avoided as much as possible in local applications.

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Photo by D A V I D S O N L U N A on Unsplash

Photo by D A V I D S O N L U N A on Unsplash

Why is it important?

The study has demonstrated the feasibility of computing local geoid heights from the differences between local and global geoid heights.

Perspectives