On the Accuracy of Geoid Heights Derived from Discrete GNSS/Levelling Data Using Kriging Interpolation

Abstract

Local geoid models presenting higher resolution than global ones are generally derived by a combination of different datasets, integrating individual pure astrogeodetic, gravimetric and GNSS/levelling solutions. To define local geoid, different interpolators may be applied starting from dataset of geoid height values. It is well known that the accuracy of the resulting models depends not only by interpolation method, but also by points numerosity and distribution. This article aims to analyse the performance of Kriging approaches in dependence of the density of the dataset. The experiments are carried out on geoid heights extracted in random way from an already existing local geoid model: different subsets are organized containing an increasing number of points in the same area and each of them is submitted to Kriging interpolations (Universal Kriging and Ordinary Kriging). The resulting models are compared with the original one and residuals are calculated to evaluate the accuracy in dependence of point density. The results demonstrate the efficiency of the Kriging methods, highlighting the possibility to achieve higher accuracy (a few centimetres) using a point density of 1 point/100 sqkm, in absence of gravity anomalies. Ordinary Kriging provides better results than Universal Kriging but the undulations between the resulting models are minimal (a few millimetres) when a high number of points is involved. Furthermore, the results highlight the limit of the leave one out Cross validation since it supplies higher residuals than direct comparison for both Universal Kriging and Ordinary Kriging, when few points are used.

Statistical Assessment of Some Interpolation Methods for Building Grid Format Digital Bathymetric Models

“…Anyway, only the bias obtained for SD1, SD2 and SD3 (lowest sampling densities) were significantly different from zero (no bias), showing a low average positive bias that, in any case, was below 10 cm. This is likely due to the fact that UK needs high sampling densities to obtain more accurate results [77]. Note that UK is prone to overestimating the actual seabed depth, since it assumes that the mean depends on spatial location [66].…”

Computation of the Height Reference Surface for the Territory of the Republic of Albania

“…The TG03 and EGM2008 models were found to be about 2 times less accurate than the precise local geoid models. Alcaras et al created a geoid model of the island of Corsica, France, which includes 81 rows and 40 columns, has a grid spacing of 1.5 in latitude and 2 in longitude, covering an area of about 24,767 km 2 [22]. It was found that ordinary kriging gives more accurate results than universal kriging, but the discrepancies between two models are minimal when there is high number of points.…”