Split-Band Interferometric SAR Processing Using TanDEM-X Data

Abstract

Most recent SAR sensors use wide band signals to achieve metric range resolution. One can also take advantage of wide band to split it into sub-bands and generate several lower-resolution images, centered on slightly different frequencies, from a single acquisition. This process, named Multi Chromatic Analysis (MCA) corresponds to performing a spectral analysis of SAR images.Split-Band SAR interferometry (SBInSAR) is based on spectral analysis performed on each image of an InSAR pair, yielding a stack of sub-band interferograms. Scatterers keeping a coherent behaviour in each subband interferogram show a phase that varies linearly with the carrier frequency, the slope being proportional to the absolute optical path difference. This potentially solves the problems of phase unwrapping on a pixelper-pixel basis.In this paper, we present an SBInSAR processor and its application using TanDEM-X data over the Nyiragongo volcano.

Elevation Changes Inferred From TanDEM-X Data Over the Mont-Blanc Area: Impact of the X-Band Interferometric Bias

“…But it could be used to first estimate the absolute height of at least one pixel for each connected component, before unwrapping the full image. This method has been recently applied to estimate the absolute altitude of the central crater of the Nyiragongo volcano using TDX data[47].The absolute phase of each disconnected areas was hence estimated by choosing, for each pixel, the integer number of 2π values that minimizes the difference between the TDX and Pléiades DEMs. This method works only because the elevation difference with Pléiades can be assumed to be less than half of the height of ambiguity.…”

Split-Band Interferometry-Assisted Phase Unwrapping for the Phase Ambiguities Correction

“…The operating and rationale of the SBInSAR processor have already been presented in [5]. In this section, we will first outline the basic principles of Split-Band Interferometry and the corresponding equations.…”

“…Frequencies of adjacent subbands are shifted of ∆ν. As stated in [5], the interferometric phase of the coregistered and spectrally decomposed images in the i th partial interferogram is expressed by:…”

“…The same test site has been considered by [4] using Cosmo-SkyMed images with a total bandwidth of 325 MHz. Another study [5] also demonstrated the potential of SBInSAR for height retrieval using a TanDEM-X bistatic pair of images of 100 MHz bandwidth over Nyiragongo volcano, but stressed the need for a larger value of the initial range bandwidth. So far, the frequency-persistent scatterers have been selected using the multifrequency phase error [6] that is an estimator of the coherence from one spectral subband to another and that quantifies the quality of the phase measurements.…”