Modelling seasonal motions at geodetic reference stations by the combination of GNSS and GRACE data at the normal equation level

BRUNINI, CLAUDIO; SÁNCHEZ L.; GALVÁN, ROMINA; DREWES, HERMANN; GENDE, MAURICIO

Copenhagen

Simposio; International Symposium Gravity, Geoid and Height Systems; 2018

International GNSS Service

We propose to extend the GNSS normal equations systems (NEQ) to estimate station coordinates (position and velocity) and vertical seasonal displacements simultaneously. The proposed model parametrizes the kinematic of the GNSS time series assuming that the verticaldisplacement in a given station is proportional to the loading-induced deformation inferred from GRACE. Our experiments combine (a)NEQ calculated on a weekly basis for the regional reference frame SIRGAS (Sistema de Referencia Geocéntrico para las Américas) over five years with (b) grids of equivalent water height (EWH) derived from GRACE for the same time span. The solution of the combined NEQ leads to the common adjustment of seven parameters per GNSS station; namely, three position coordinates at a certain epoch, three constant velocity coordinates, and one parameter representing the factor of proportionality between displacements measured with GNSS and loading-induced deformations inferred from GRACE. After solving the combined NEQ iteratively, thecomparison of the station motions observed by GNSS with the deformations predicted with our approach shows an agreement of ±3 mm at the one sigma level.