COMPARISON AMONG DIFFERENT TECHNIQUES OF PREDICTING GEOID UNDULATION

Document Type : Original Article

Authors

1 Lt col. Officer, research student for M.sc. degree M.T.C.

2 Assistant professor, Ain Shams faculty of engineering, Ain Shams University, Cairo, Egypt.

3 Assistant professor, Shoubra faculty of engineering, Cairo, Egypt.

4 Military technical college, Cairo, Egypt.

Abstract

The height measurements by Global Positioning System ,GPS, which
measures the heights with respect to the reference ellipsoid make confusion with
the height of Mean Sea Level (MSL) which determined with respect to geoid. The
datum that defines the MSL (also called the geoid) is a complex surface that
requires dense and accurate data to define its shape.
In this study, ellipsoidal heights of data points were determined from GPS
measurements, with respect to WGS84 reference ellipsoid, and we know
accurately the undulation of these points at specific locations inside the cairo
city. The objective of this research is to predict the undulation of unknown points
by using different prediction techniques.
Four different prediction methods were used to determine geoid undulation.
These methods are: inverse distance weighting method, triangulation method,
radius search method, and nearest neighbor method.
Comparison among different techniques were applied. Distance as a
common variable for all different techniques is used to compare the accuracy for
the different resulted values of Geoid undulation. Most results show that the
triangulation
prediction method is the best for prediction of Geoid undulation.

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