Atmospheric Phase Delay in Sentinel Sar Interferometry

Abstract

Commission III, WG III/3 KEY WORDS: Interferometric SAR, differential interferometry, tropospheric path delay ABSTRACT:The repeat-pass Synthetic Aperture Radio Detection and Ranging (RADAR) Interferometry (InSAR) has been a widely used geodetic technique for observing the Earth's surface, especially for mapping the Earth's topography and deformations. However, InSAR measurements are prone to atmospheric errors. RADAR waves traverse the Earth's atmosphere twice and experience a delay due to atmospheric refraction. The two major layers of the atmosphere (troposphere and ionosphere) are mainly responsible for this delay in the propagating RADAR wave. Previous studies have shown that water vapour and clouds present in the troposphere and the Total Electron Content (TEC) of the ionosphere are responsible for the additional path delay in the RADAR wave. The tropospheric refractivity is mainly dependent on pressure, temperature and partial pressure of water vapour. The tropospheric refractivity leads to an increase in the observed range. These induced propagation delays affect the quality of phase measurement and introduce errors in the topography and deformation fields. The effect of this delay was studied on a differential interferogram (DInSAR). To calculate the amount of tropospheric delay occurred, the meteorological data collected from the Spanish Agencia Estatal de Meteorología (AEMET) and MODIS were used. The interferograms generated from Sentinel-1 carrying C-band Synthetic Aperture RADAR Single Look Complex (SLC) images acquired on the study area are used. The study area consists of different types of scatterers exhibiting different coherence. The existing Saastamoinen model was used to perform a quantitative evaluation of the phase changes caused by pressure, temperature and humidity of the troposphere during the study. Unless the phase values due to atmospheric disturbances are not corrected, it is difficult to obtain accurate measurements. Thus, the atmospheric error correction is essential for all practical applications of DInSAR to avoid inaccurate height and deformation measurements.

Mitigating Atmospheric Effects in InSAR Stacking Based on Ensemble Forecasting with a Numerical Weather Prediction Model

“…The hydrostatic part can be calculated using Equation ( 6) ZHD = 2.2779 × P s 1 − 0.00266 cos(2θ) − 0.00028H 0 (6) where P s is the measured total surface pressure (hPa), θ is the latitude ( • ), and H 0 is the surface height (m).…”

“…Atmospheric delay consists of two major components: the ionospheric effect and the tropospheric effect [6]. The ionospheric delay is dispersive [7], meaning that it is inversely proportional to the signal frequency.…”

Assessment of Land Deformation and the Associated Causes along a Rapidly Developing Himalayan Foothill Region Using Multi-Temporal Sentinel-1 SAR Datasets

“…However, electromagnetic waves exhibit significant phase errors while propagating through the various atmospheric layers [35][36][37]. Other errors observed in the SAR interferometric techniques are typically the temporal decorrelation and the phase unwrapping errors, which often result in uncertainty in the interferometric phases and the corresponding LOS observations of elevation and displacement [26,38,39].…”