Combining high resolution global geopotential and terrain models to increase national and regional geoid determinations, Maracaibo Lake and Venezuelan Andes case study

Abstract

The combination of global geopotential earth models with high resolution digital terrain models forms the main tool for geoid modelling and satisfies the requirements at a wide range of gravity field frequencies. The need for local and regional data can be reduced to minor areas around points of interest. The resolution gap between potential models and digital terrain models is narrowing - EGM08 and SRTM, for instance, going down to 5′- and 3″-spacing, respectively. The influence of regional gravity data or other field components is reduced to a limited area zone. This means a significant advantage particularly in the case of developing countries which normally demonstrate heterogeneous data quality, bad geographical distribution or complete lack of local data sources at all. Using as test area the Maracaibo Lake and the Venezuelan Andes region - an area with a 4,000 m height variation and some major height changes caused by natural or human based environmental hazards-, a recent GPS project dedicated to precise satellite observations over points of the first order leveling network in the area was performed. Applying most rigorous processing techniques, ellipsoidal height determinations at the 1-3 cm level were achieved at the 2008 campaign. Agreement between GPS/Leveling measurements and modeled geoid values improved. Comparing the new data with GPS observations dating from 1993 to 1998 - which formed a crucial part of the previous national geoid determination -, showed the limitations of the applied technique, partly explainable by height changes occurring in the area. An increasing epoch difference between new data sets and the original observations of the leveling network contributes in the differences, too. ©Springer-Verlag Berlin Heidelberg 2012.