Abstract:
Single-pass interferometric synthetic aperture radar (InSAR) elevation measurements of dry snow, firn, and ice are known to be substantially biased downward due to a part...Show MoreMetadata
Abstract:
Single-pass interferometric synthetic aperture radar (InSAR) elevation measurements of dry snow, firn, and ice are known to be substantially biased downward due to a partial penetration of the radar signals into the medium, resulting in a phase center location within the volume. The so-called penetration bias, i.e., the elevation difference between surface and InSAR phase center, can be estimated from the contribution of the volume to the interferometric coherence and may be used to retrieve the surface elevation. In this article, we show that both an additional elevation bias and a horizontal shift occur in the InSAR processing for natural media with a dielectric constant different to the one of air, originating from an uncompensated stretch of the vertical wavenumber in the medium and refraction effects at the surface. This geolocation error depends on the magnitude of the penetration bias, the dielectric constant, and the acquisition geometry. It may reach up to few meters for X- and C-band frequencies and more for lower frequencies and therefore may significantly affect cryospheric elevation products from past (SRTM), current (TanDEM-X), and future (e.g., Harmony and Tandem-L) SAR interferometers. In this article, the geolocation error is assessed and an adapted interferometric processing allowing for an accurate geolocation (i.e., surface elevation measurement) is presented.
Published in: IEEE Transactions on Geoscience and Remote Sensing ( Volume: 62)