Comparison of Geoid Determination Methods: A Case Study at the Central Part of Ethiopia.
No Thumbnail Available
Date
2024-02
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
Geoid is the equipotential surface that closely approximates to the mean sea level.
Determining the geoid gravimetrically poses challenges, particularly when demanding
precision is necessary. The precision of geoid determination depends on the methods that
were applied during computation. The paper aimed at comparing the magnitude of geoid
ellipsoidal separation which obtained from the three distinct geoid determination methods
namely: the least square collocation, Stokes integral, and Hotine integral methods with an
emphasis on evaluating their individual accuracies. SRTM1, gravity anomaly and
disturbance, EGM08 and GPS/Levelling data were used for the computation of geoid
determination methods. The downward continuation of the free-air gravity anomaly was
performed for both the Stokes integral and least square collocation methods, and the gravity
disturbance for Hotine integral method were used. In addition to this, the corrections were
added for Stokes and Hotine integral methods to the approximate geoid. During comparison
of the computed gravimetric geoid models, the GPS/leveling data was taken as a reference for
validation. The standard deviation of the least square collocation, Stokes and Hotine integral
methods were 0.154m, 0.061m, and 0.062m, respectively. Based on the standard deviation the
Stokes integral, Hotine integral, and least square collocation methods demonstrated high,
medium, and low accuracy, respectively, across diverse topographies. However, in plain
areas, all the methods that applied in this study are significant for geodetic community.
Whereas, in mountainous regions, only the Stokes and Hotine integral methods are preferred
and had achieved effective accuracy. And also, the F-test statistics between the least square
collocation and the Stokes/Hotine/ integral methods showed significance difference.
Therefore, the least square collocation method needs further investigation to attain the
permissible accuracy similar to Hotine and Stokes integral methods.
Description
Keywords
Free air anomaly, Geoid, Gravity disturbance, Hotine integral, Least square collocation, Stokes integral