Ersoy ARSLAN, Mehmet YILMAZ

İstanbul metropolitan alanında geoit araştırması

Geoit uydularla belirlenen elipsoidal yükseklik ile nivelman ölçmeleriyle belirlenen ortometrik yükseklik arasındaki doğal bir bağdır. Geoit belirleme, enlem ve boylamı bilinen herhangi bir noktadaki geoit yüksekliğinin belirlenmesidir. Presizyonlu İstanbul geoidini belirlemek için hesaplamalarda enlem, boylam, elipsoidal ve ortometrik yükseklikleri bilinen 393 nokta, hesapların kontrollerinde ise 50 nokta kullanılmıştır. Geoit belirleme yöntemlerinden EGM96 yeryuvarı modeli ve GPS/nivelman yöntemi ile hesaplar yapılmıştır. Polinom katsayıları ve bulanık mantık yöntemi ile geoit belirlemede GPS/nivelman yöntemine göre belirlenen geoit yükseklikleri veri olarak kullanılmıştır. Bulanık mantık yöntemiyle en presizyonlu sonuçlar elde edilmiştir.

Geoid research in Istanbul metropolitan area

Geoid is called the surface which is constituted points that gravitational potential constant and close to Mean Sea Level. Geoid is a complex surface and can not be defined as mathematically. In geodesy, measurements are done on physical topography, however, computations are done on the ellipsoid whose dimensions are determined. However, geoid and ellipsoid can not be collided with each other and there would be a difference between when center of these two surfaces were collided at the center of gravity. The difference between these two surfaces is called geoid height. Geoid determination is computation of geoid height on a point whose latitude and longitude are known. Precise geoid determination became one of the most important problems in geodesy by developed satellite techniques. The reason for this is that geoid height is the only tie between ellipsoidal height obtained by satellite measurement and orthometric height obtained by leveling. 393 points whose latitudes and longitudes known are used to determine precise Istanbul geoid and 50 points used for testing of calculations. Of the geoid determination methods, EGM96 geopotential method and GPS/leveling methods are used. Geoid heights obtained from GPS/leveling method are used as data in polynomial coefficients and fuzzy logic method. Fuzzy logic method is the most precise methods of all.

PDF

___

Ayan T., Aksoy A., Çelik R.N., Deniz R., Arslan E., Özşamlı C., Denli H.,Erol S., Özöner B.,. (1999). İstanbul GPS Nirengi Ağı (İGNA) Teknik Rapor, İstanbul Teknik Üniversitesi İnşaat Fakültesi Jeodezi Anabilim Dalı, İstanbul, Kasım.
Akyılmaz O., Ayan T., Özlüdemir T., (2003). Geoid surface approximation by using Adaptive Network based Fuzzy Inference Systems, AVN 308-315.
Banarjee, P., Foulger, G.R., Satyaprakash, and Dabral, C.P., (1999). Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data, Journal of Geodesy, 73, 79-86.
Grafarend, E. W., (1994). What is geoid?, Geoid and its geophysical interpretations, edited by Petr Vanicek and Nikolas T.Christou, Chapter 1, CRC press, Boca Raton, FL, USA.
Heiskanen, W.H., Moritz, H., (1967). Physical Geodesy, Freeman, San Fransisco, USA.
Sevilla M. J., (1996). A new gravimetric geoid in the Iberian Peninsula, Joint Special Issue of the of the Bureau Gravimétrique Intarnational Bulletin d'Information No. 77 and International Geoid Service Bulletin No. 4, 163-180.
Sjöberg, L. E., (1994). Techniques for geoid determination, Geoid and its geophysical interpretations, edited by Petr Vanicek and Nikolas T.Christou, Chapter 2, CRC press, Boca Raton, FL, USA.
Yılmaz M., (2005). İstanbul Metropolitan Alanında Geoit Araştırması, Doktora Tezi, İTÜ Fen Bilimleri Enstitüsü, İstanbul.