GNSS in Practical Determination of Regional Heights - Global Navigation Satellite Systems: Signal,Theory and Applications - page 152

reference benchmarks must be at least 1 benchmark per 15 km 2 for determination of precise
local geoid with geometric approach (LSMSDPR, 2005; Deniz&Çelik, 2008), however with
the purpose of testing and local improvement of the regional geoid, the density of the
reference GNSS/levelling benchmarks are foresighted to be at least 1 benchmark per 200
km 2 by the regulation.
Longitude (°E)
Fig. 14. Çankırı geoid reference benchmarks on topography (Erol et al., 2008)
In respect of the case study carried out with Çankırı local GNSS/levelling network by Erol
et al. (2008), Turkish regional geoid TG03 (TNUGG, 2003; Kılıçoğlu et al., 2005) was tested at
31 GNSS/levelling benchmarks, and refined by combining the GNSS/levelling heights
using least squares adjustment (LSA) of height differences derived from GNSS ellipsoidal
heights and TG03 geoid undulations on the baselines, and simple corrector surface model
(CS) with only a bias and a tilt. The performances of the refinement methods were also
compared in terms of geoid height residuals at the 9 test points of 31 benchmarks. In
addition, LSA of the geoid height differences on the baselines approach was applied with
estimated variance components of each height sets, using iterative Minimum Quadratic
Unbiased Estimation. The performances of TG03 and its refined versions were also
compared with local GNSS/levelling geoid model which were determined with
GNSS/levelling heights at 22 reference benchmarks using a 2 nd order polynomial equation
in the study. Considering the reported results, the accuracy of TG03 model is ±26.2 cm in
terms of RMSE of geoid heights and the mean of geoid height differences at the benchmarks