Vertical Gravity Gradient Modeling by 3-D Least Squares Collocation and its impact on quasigeoid-geoid separation term

European Geosciences Union General Assembly 2020, Vienna, Avusturya, 4 - 08 Mayıs 2020, ss.1-2

For the quasi-geoid determination by 3-D Least Squares Collocation (LSC) in the context of

Molodensky’s approach, there is no need to measured or modelled vertical gravity gradient (VGG)

as the 3-D LSC takes the varying heights of the gravity observation points into account. However,

the use of measured or modelled VGG instead of the thereotical value is expected to improve the

quasigeoid-geoid separation term particularly in mountainous areas. The VGG measurements are

found to be different from the theoretical value in the range of - % 25 and + % 39 in western

Turkey. Previously there has been no study using modelled VGGs for gravimetric geoid modelling

in Turkey. VGGs are modelled by 3-D Least Squares Collocation (LSC) in remove-restore approach

and validated by terrestrial VGG measurements in western Turkey. The effect of using modelled

VGG instead of the theoretical one in quasigeoid-to-geoid separation term is found to be

significant. The quasi-geoid computed by 3-D LSC in western Turkey is converted to geoids using

theoretical or modelled VGG values and compared with GPS/levelling geoid-undulations.