High resolution ZTD maps from SIRGAS-CON Network in Central West Argentina

PATRICIA A. ROSELL; VIRGINIA MACKERN; PABLO A. EUILLADES; LEONARDO D. EUILLADES; LAURA MATEO

Río de Janeiro

Simposio; Simposio Internacional SIRGAS (Sistema de Referencias Geocéntrico para las Américas); 2019

International Association of Geodesy

Troposphere is a layer of the atmosphere which extends from Earth's surface to an altitude of 10-15 km above sea level. In its lowest part, variation in pressure, temperature and water vapor pressure change the refractivity index resulting in a delay of electromagnetic waves that break through it.Signal is slowed down, its path a little bit bended and travel time increases. This generate a lengthening, known as Zenith Total Delay (ZTD), affecting measurement of the coordinates from GNSS antennas for it need to be determinate and applied as a correction. SIRGAS generates ZTD from its antennas (every 1 or 2 hours) and this product can be used for atmospheric corrections in Synthetic-aperture Radar (SAR) images. The aim of this project is generate continues ZTD maps for later SAR corrections (pixel-by-pixel), at specific time and dates.In this work, we show the results of applying an Iterative Decomposition model (ITD) profiting data from SIRGAS-CON Network for creating high resolution ZTD maps. The area of interest (AOI) is focused over San Juan Province, Central West Argentina, including part of the Central Andes where a high topographic relief is present. Temporal data set covers 83 dates from October 2014 to April 2018 at 10 UTC whilst AOI is approximately 130 km x 80 km with a spatial resolution of 15 m x 15 m.We used SIRGAS-CON stations within a range of 200 km allowing us to process data of six antennas (CSLO, MZAC, MZAE, MZAU, UNSJ and SANT), two of them inside the study area (CSLO and UNSJ). A ZTD value was obtained for each pixel. In order to evaluate those values, we remove CSLO and UNSJ from processing and a ZTD value was calculated for those cells within stations. Average differencesbetween real and interpolated values are in the order of 0.05 m for CSLO and 0.01 m for UNSJ. Generated maps show continues values of ZTD for epochs in which data is available but noticeable discontinuities can be seen for those areas where both small number and different stations are used. Nevertheless, this interpolation model allows us to obtain high resolution maps over anextended area that will be improved as the GNSS network grows in density.