GPS tomography tests for DInSAR applications on Mt. Etna

Massimo Aranzulla Massimo Aranzulla,Giuseppe Puglisi Giuseppe Puglisi

doi:10.4401/ag-6750

Massimo Aranzulla Massimo Aranzulla, Giuseppe Puglisi Giuseppe Puglisi

Open Access

https://doi.org/10.4401/ag-6750

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Abstract

<p>Tropospheric artifacts of SAR images in a volcanic area like Mt. Etna cause ambiguity in the interpretation of deformations with such technique. It would be useful to measure the delay caused by tropospheric anomalies in synthetic aperture radar (SAR) satellite signals (phase of the back-scattered radar wave) that could be interpreted as deformation. From the delay estimated through the GPS data processing, the tropospheric tomography of electromagnetic waves refractivity, has been performed using the SIMULps12 software. The aim of this study was to perform software synthetic tests by using SIMULps12 applied to atmospheric tomography and to verify the influence of the different GPS geodetic network configurations on obtaining a reliable tomography. Three different anomalies of increasing complexity have been investigated in order to understand the representative parameters of a correct tomography, the best spatial resolution and the portions of space in which the tomography is reliable. The tests also focused on fixing/establishing the a-priori atmospheric model and the critical values of the main parameters involved in the tomographic inversion. To this end, we made a random choice of two days, necessary to define the tomographic problem. Three different network configurations with 15, 30 and 90 GPS receivers were studied. The results indicate that the well-resolved area of tomographic images increases with the number of GPS receivers not linearly, and that the actual GPS network of 42 receivers is capable of revealing/detecting the atmospheric anomalies.</p>

Highlights

Differential synthetic aperture radar (SAR) (Synthetic Aperture Radar) interferometry (DInSAR) is a satellite-based technique used frequently today to measure the shape of the Earth and its variation in time.The measurement of ground deformations with DInSAR technique is based on the comparison between two SAR images acquired at different times
Starting from the previous studies [Bonforte et al 1999, Bonforte et al 2001, Bruno et al 2007], we propose some advances aimed at assessing a method to obtain a suitable tomography of EM waves propagation velocity of the lower atmosphere, from delays measured by the Mt
GPS is commonly used to estimate the delays of EM waves through the atmosphere and some studies have recently exploited this characteristic to obtain tomographies [Hirahara 2000, Hoeven et al 2002, Nilsson and Gradinarsky 2006, Nilsson et al 2007], few studies have been conducted on Mount Etna

Summary

Introduction

Differential SAR (Synthetic Aperture Radar) interferometry (DInSAR) is a satellite-based technique used frequently today to measure the shape of the Earth and its variation in time. The measurement of ground deformations with DInSAR technique is based on the comparison between two SAR images acquired at different times (called interferograms). If ground deformation occurs between two satellite passes in the same area, the path differences between the sensor and the ground (through the two passes) lead to a difference in the phase of the back-scattered radar wave [Ulaby et al 1986, Massonnet et al 1993]. The neutral atmosphere (stratosphere and troposphere) is the portion of the atmosphere where the variations that significantly affect the interferograms occur. In areas with prominent topography, such as the volcanoes, atmospheric heterogeneities are relatively frequent and yield the use of DInSAR technique for monitoring purposes in such areas critical

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