Ecuadorian Vertical Datum Link to the International Height Reference System
21/09/2016 | 17:15 | Session 5: Height systems and vertical datum unification
Author(s): José Carrión, Sílvio Correia de Freitas and Riccardo Barzaghi
José Carrión, Sílvio Correia de Freitas and Riccardo Barzaghi
The continue development of spatial technologies has allowed to apply new methodologies to carry out geodetic surveys, with clear advantages in terms of resources optimization and products quality. When it is required to integrate the information that comes from global information sources with local information, it is essential to discriminate among different spatial reference systems, which are adopted by various observation techniques. In this context, Geodesy studies the suitable mechanisms to link the Local Vertical Reference Systems (LVRSs) with a Global Vertical Reference System (GVRS), thus allowing the LVRS homogenization and its compatibility with the global information sources. To achieve this objective, it is necessary to define and materialize a Global Vertical Datum (GVD) and besides know the relationship with the Local Vertical Datums (LVDs). Height determination in Ecuador has been established locally by adopting as Vertical Datum (VD) the Mean Sea Level (MSL) determined for a specific reference epoch. It is then required to explore a suitable methodology to address the Ecuadorian VRS case in the context of the International Height Reference System (IHRS) establishment. This implies the consequent modernization of the LVRSs according to the precepts disclosed by the International Association of Geodesy (IAG). In this work it was computed the discrepancy between the Ecuadorian Vertical Datum (EVD) and the GVD in terms of geopotential values. Local gravity information from heterogeneous sources is complemented by the spectral decomposition technique, using Global Geopotential Models (GGMs) and the effects of the residual topography (Residual Terrain Model - RTM). The heterogeneity of the gravity information, in terms of estimated precisions and spatial and physics referential, is an important aspect to be considered. In this respect, the Least Square Collocation (LSC) method allowed to modelling the residual quantities into the EVD region from heterogeneous data for later apply the Geodetic Boundary Value Problem (GBVP) solution in the fixed form. The results show consistency and will be contrasted with those that will be obtained from an oceanographic approach.