M.Sc. Tezi Görüntüleme

Student:	Kemal YURT
Supervisor:	Ass. Prof. Dr. Ertan GOKALP
Department:	Geodesy and Fotogrammetry Engineering
Institution:	Graduate School of Natural and Applied Sciences
University:	Karadeniz Technical University, Turkey

Title of the Thesis:	Local Geoid Determination and Modeling by Geometric and Gravimetric Methods: Case Study for Trabzon Municipilaty
Level:	M.Sc.
Acceptance Date:	29/9/2006
Number of Pages:	173
Registration Number:	i569

Summary:

Thanks to great advances in GPS technology, the positioning precision in horizontal and vertical directions has also improved. The studies to obtain orthometric heights from only GPS measurements have increased. In this study, it is aimed to determine the geometric and gravimetric local geoids of a small area (approximately 30 km2). To obtain the orthometric heights from GPS measurements, without any need to leveling measurements,is the main purpose of this study. It is also examined that which model is the most

convenient by comparing the determined geoid models.

In order to achieve these purposes, a region including the city center of Trabzon has been chosen as study area. 39 points have been established in this area and they have been connected with TUTGA points to assign coordinates to them. The heights of these points have been derived from geometric leveling that has a root mean square error (RMSE) ± 5.03 mm. The RMSE of GPS/Leveling geoid model is obtained as ± 8.5 mm. In

determining the gravimetric geoid, WGS84 EGM96 and Remove-Restore techniques have been used. In the methods in which the geopotential models EGM96 and OSU91A have been used, the contribution of gravity to geoid has been obtained by Stokes-Kernel function and FFT methods which has spherical approach and planar approach,

respectively. The most precise result has been achieved as ± 7.4 cm by spherical approach in which EGM96 geopotential model has been used.

After determining the geoid undulations, multiquadratic geoid surface models have been constituted for the study area. The second order orthogonal polynomial surface has been chosen as trend surface for the multiquadratic surface, since it has passed the significance test and the RMSE of unit weight of it is ± 22.8 cm. At the end of testing the GPS/Leveling multiquadratic geoid surface model with field measurements, the difference has been obtained as 1.7 cm with a RMSE ± 1.4 cm. As a consequence, it is possible to obtain the geoid undulations of the points with an accuracy of 2 cm by means of the product GPS/Leveling geoid surface model.