OFFSET EVALUATION OF THE ECUADORIAN VERTICAL DATUM RELATED TO THE IHRS

José L Carrión Sánchez,Sílvio R C De Freitas,Riccardo Barzaghi

doi:10.1590/s1982-21702018000400031

José L Carrión Sánchez, Sílvio R C De Freitas + Show 1 more

Open Access

https://doi.org/10.1590/s1982-21702018000400031

Copy DOI

Abstract

Abstract Considering the definition of the International Height Reference System (IHRS) in the geopotential space (Resolution 1/2015, International Association of Geodesy - IAG), among the present main objectives of the international geodetic community is the materialization of IHRS around the world. One fundamental task for this is the offset determination of each national vertical datum related to the IHRS. In this manuscript we establish the relationship between the Ecuadorian Vertical Datum (EVD) and the IHRS in the geopotential space following the foundations of the Resolution 1/2015 IAG. Gravity data, heights from the Ecuadorian Fundamental Vertical Network, Global Geopotential Models and Digital Elevation Models were used in the computations. Based on the Least Squares Collocation method, empirical covariance functions and spectral decomposition techniques, we realized the modelling of the geopotential in the study region (4° x 4° centered in the La Libertad tide gauge, Ecuador). Based on the referred approaches, we solved the free Geodetic Boundary Value Problem for determining the discrepancy of the EVD related to the IHRS. An offset of approximately 29 cm ± 3 cm was estimated for the W 0 - W 0 i relation when the GO_CONS_GCF_2_DIR_R5 model was used in the modeling of the medium and long wavelengths of the terrestrial gravity field, and approximately 43 cm ± 3 cm when the EIGEN6C4 model was used.

Highlights

The International Association of Geodesy (IAG) establishes a coordinated approach for monitoring global changes inside the Global Geodetic Observing System (GGOS)
GMGGM − rγ where GMGGM is the geocentric universal gravitational constant related with the Global Geopotential Models (GGMs) and GMGRS is the geocentric universal gravitational constant related with the geodetic reference system
The geopotential value (W0i) computation were carried out on the reference level corresponding to the Mean Sea Level (MSL) determined for the period 1988 2009 and materialized on the fundamental bench mark (BM03 - origin of the EVRN)

Summary

Introduction

The International Association of Geodesy (IAG) establishes a coordinated approach for monitoring global changes inside the Global Geodetic Observing System (GGOS). An essential aspect which must be considered, is that the discrepancy of each Vertical Datum (VD) to the referred global equipotential surface propagates to each functional which depends on the heights (e.g. gravity anomalies). This is the called VD indirect effect (Gatti, Reguzzoni and Venuti, 2012). To avoid this problem, it is necessary to refer all national VDs to the same global equipotential surface

Methods

Results

Conclusion