Determination of Geoid Heights by GPS and Precise Trigonometric Levelling

Abstract

Most commonly used method for the determination of geoid is the evaluation of GPS (Global Positioning System) and levelling measurements together. Despite the fact that geometric levelling (GL) is in general easy and practicable, it is a measurement method that is hard and uneconomic to apply particularly in mountainous, hilly and rugged areas. This study aims the use of precise trigonometric levelling (PTL) method instead of GL for the determination of precise geoid heights. The method has been probed into in consideration of the accuracy, practicability, measurement and evaluation criteria, and has been compared with GL measurement results. In addition, geoid profiles that have been determined both (GPS_GL) and (GPS_PTL) measurements have been compared with TG-99A (Turkish Geoid-1999A) and IGNA (Istanbul GPS Network) geoid models to explore their consistency.

Performance evaluation of the Earth Gravitational Model 2008 (EGM2008) – a case study

“…This is a great achievement in the fields of geodesy and geophysics since we can obtain heights with physical meaning without necessarily carrying out the tedious and time-consuming procedures of obtaining these heights by geometric or trigonometric levelling (Hirt, et al, 2011. The EGM08 derived geoid heights can reach the accuracy of regional or local geoid models after modelling the differences between the GPS/levelling geoid heights and EGM08 derived geoid heights at identified control points (Dawod, 2008;Dawod et al, 2010;Soycan, 2014).…”

Improving EGM2008 by GPS and leveling data at local scale

“…In recent applications, approaches were adopted to determine long wavelength effects utilizing the earth's potential coefficients, medium wave length effects utilizing gravity, and short and ultra-short wavelength effects utilizing combined methods (KIAMEHR, andSJOBERG 2005, BENAHMED DAHOA et al 2006;FEATHERSTONE and SPROULE, 2006;KOTSAKIS and KATSAMBALOS, 2010) Particularly, following the improvements on GNSS (Global Navigation Satellite Systems) technology, the researches focusing on obtaining "cm" level geoid accuracy attracts attention in the 2000's. The geometric modeling with GPSleveling method come to the fore in studies for the determination of short and ultrashort wavelength components of geoid in those years (IAG,1995;OLLIKAINEN, 1997;SOYCAN and SOYCAN, 2003;SOYCAN, 2006). Recently, a great attention has been paid to the precise determination of local/ regional geoids, aiming at replacing the GPS-leveling method with the improvement of accurate geopotential models.…”

Analiza geostatističnega modela površja za višinsko transformacijo gps: študija primera na območju Izmirja v Turčiji

“…The recent geodetic research has focused on obtaining "cm" level geoid both in theoretical and practical studies, e.g. Vanicek and Kleusberg, 1987;Li and Sideris, 1994;Tóth et al, 2000;Kühtreiber, 2002;Chen et al, 2003;Soycan, 2006a;Abbak et al, 2012. Geoid is simply defined as the equipotential surface of the Earth's gravity field which best fits, in a least-squares sense, global mean sea level.…”

“…In particular, it is difficult to predict the local effects of the geoid by the global or regional geoid models. A more detailed local surface model is needed for the determination of short and ultra-short wavelength (IAG, Soycan and Soycan 2003;Soycan, 2006a;Soycan, 2006b;Stopar et al, 2006;Erol et al, 2008). The height differences derived from GPS and levelling data are the highest quality and most reliable data to predict the local effects.…”