Indoor experiments on polarimetric SAR interferometry

Abstract

Abstract-A coherence optimization method, which makes use of polarimetry to enhance the quality of SAR interferograms, has been experimentally tested under laboratory conditions in an anechoic chamber. By carefully selecting the polarization in both images, the resulting interferogram exhibits an improved coherence above the standard HH or VV channel. This higher coherence produces a lower phase variance, thus estimating the underlying topography more accurately. The potential improvement that this technique provides in the generation of digital elevation models (DEM) of non-vegetated natural surfaces has been observed for the first time on some artificial surfaces created with gravel. An experiment on a true outdoor DEM has not been accomplished yet, but the first laboratory results show that the height error for an almost planar surface can be drastically reduced within a wide range of baselines by using the optimization algorithm. This algorithm leads to three possible interferograms associated with statistically independent scattering mechanisms. The phase difference between those interferograms has been employed for extracting the height of vegetation samples. This retrieval technique has been tested on three different samples: maize, rice, and young fir trees. The inverted heights are compared with ground truth for different frequency bands. The estimates are quite variable with frequency, but their complete physical justification is still in progress. Finally, an alternative simplified scheme for the optimization is proposed. The new approach (called polarization subspace method) yields suboptimum results but is more intuitive and has been used for illustrating the working principle of the original optimization algorithm.

Polarimetric Optimization of Temporal Sublook Coherence for DInSAR Applications

“…As shown later, due to the parallelism between the coherence estimator and the TSC approach, it is possible to extend this method to work with the Best [5], SOM [9], and ESM [10] polarimetric optimization methods.…”

“…Nonetheless, this approach does not fully benefits from the potentials of polarimetry. The following methods, referred to as SOM [9] and ESM [10], make use of PolSAR data in a more efficient way.…”

“…The objective is to improve the TSC performance in terms of both phase quality and pixels' density. In this framework, the polarimetric optimization methods referred to as Best [5], SubOptimum Scattering Mechanism (SOM) [9], and Equal Scattering Mechanism (ESM) [10] are adapted to work with the TSC approach.…”

The development of a ground based polarimetric SAR interferometer (GB-POLInSAR)

“…The data set selected for OVOG model investigation is an indoor measurement (hence free of temporal decorrelation) of a maize sample collected at the JRC-EMSL facility [6]. The sample consists of a tall stand of 6 x 6 plants with a height of 1.8m planted in a square container of size 2m.…”

“…Ground based radar observations are not new. Various scatterometers [3], imaging GB-SAR systems [4,5] and 3-D imagers [2,6] have been developed and deployed. More recently ground-based interferometers have also been widely used for monitoring subsidence and other small displacements [7].…”