Monitoring ground deformation using SAR interferometry (InSAR) sometimes requires the introduction of coherent radar targets, especially in vegetated nonurbanized areas. Passive devices such as ...corner reflectors were used in such areas in the past. However, they suffer from drawbacks related to their large size and weight, conspicuousness, and loss of reliability because of geometric variations as well as material and maintenance-related degradation over several years of deployment. The viability of smaller, lighter, and less conspicuous radar transponders as an alternative is demonstrated via two field experiments: validation tests in a controlled environment, and operational performance for monitoring landslides in a heavily vegetated area. Comparison of 113 transponder-InSAR observations with independent validation measurements such as leveling and the global positioning system yields an empirical precision range of 1.8-4.6 mm, after outlier removal, for double-difference (spatial and temporal) transponder phase measurements in the radar line of sight, for Envisat and ERS-2.
Persistent scatterer interferometry (PSI) is capable of millimetric measurements of ground deformation phenomena occurring at radar signal reflectors (persistent scatterers, PS) that are phase ...coherent over a period of time. However, there are also limitations to PSI; significant phase decorrelation can occur between subsequent interferometric radar (InSAR) acquisitions in vegetated and low-density PS areas. Here, artificial amplitude- and phase-stable radar scatterers may have to be introduced. I2GPS was a Galileo project (02/2010–09/2011) that aimed to develop a novel device consisting of a compact active transponder (CAT) with an integrated global positioning system (GPS) antenna to ensure millimetric co-registration and a coherent cross-reference. The advantages are: (1) all advantages of CATs such as small size, light weight, unobtrusiveness and usability with multiple satellites and tracks; (2) absolute calibration for PSI data; (3) high sampling rate of GPS enables detection of abrupt ground motion in 3D; and (4) vertical components of the local velocity field can be derived from single-track InSAR line-of-sight displacements. A field trial was set to test the approach at a potential landslide site in Potoška planina, Slovenia to evaluate the applicability for operational monitoring of natural hazards. Preliminary results from the trial highlight some of the key considerations for operational deployments in the field. Ground motion measurements also allowed an assessment of landslide hazard at the site and demonstrated the synergies between InSAR and GPS measurements for landslide applications. InSAR and GPS measurements were compared to assess the consistency between the methods from the slope mass movement detection aspect.
Geodetic Network Design for InSAR Mahapatra, Pooja S.; Samiei-Esfahany, Sami; Hanssen, Ramon F.
IEEE transactions on geoscience and remote sensing,
07/2015, Letnik:
53, Številka:
7
Journal Article
Recenzirano
Ground deformation can be monitored with subcentimetric precision from space, using interferometric synthetic aperture radar (InSAR). This technique can sometimes be limited by a low density of ...naturally occurring phase-coherent radar targets. Measurement densification may be achieved through improvements in processing algorithms and new satellites with better revisit times, but there can still exist areas where very few coherent targets are detected, e.g., in vegetated nonurbanized areas. For third-party end users of InSAR survey results, there is currently no systematic method to determine a priori whether these coherent targets have adequate spatial distribution to estimate the parameters of their interest. We propose such a method, along with a practical solution for measurement densification, i.e., deployment of coherent target devices such as corner reflectors or transponders. We propose a generic network design methodology that does the following: 1) determines whether the naturally occurring InSAR measurements are adequate; 2) finds the minimum number of additional devices (if required); and 3) finds their optimal ground locations. The method digests, as inputs, the expected locations and quality of existing coherent targets, the quality of the devices being deployed, and, if available, any prior knowledge of the deformation signal. At the core of the method is a comparison of different covariance matrices of the final parameters of interest with a criterion matrix (i.e., the desired idealized covariance matrix), using a predefined metric. The resulting network is optimized with respect to precision, reliability, and cost criteria. Simulated data sets and a subsidence case study in the Netherlands are used to demonstrate this method.
Deformation estimates from Interferometric Synthetic Aperture Radar (InSAR) are relative: they form a ‘free’ network referred to an arbitrary datum, e.g. by assuming a reference point in the image to ...be stable. However, some applications require ‘absolute’ InSAR estimates, i.e. expressed in a well-defined terrestrial reference frame, e.g. to compare InSAR results with those of other techniques. We propose a methodology based on collocated InSAR and Global Navigation Satellite System (GNSS) measurements, achieved by rigidly attaching phase-stable millimetre-precision compact active radar transponders to GNSS antennas. We demonstrate this concept through a simulated example and practical case studies in the Netherlands.
Applying time-series InSAR to measure crustal deformation in vegetated non-urbanized areas often yields a low density of measurement points (persistent scatterers or PS). Algorithmic improvements and ...new sensors with better revisit times can improve measurement densities, but there still exist areas with heavy decorrelation from where almost no coherent information can be extracted. We propose a new scheme that determines the optimal density and locations of introduced in situ devices (e.g. passive corner reflectors or active transponders) for measuring deformation within the constraint of a desired optimality criterion. The scheme digests, as input, prior knowledge of the expected deformation signal, (probable) PS locations, PS quality and device measurement precision. We demonstrate this scheme through a simulated dataset and a ground subsidence case study in the Netherlands.
The geodetic quality of a low-cost commercial off-the-shelf InSAR transponder has been empirically assessed, both under controlled conditions and operationally for landslide monitoring. Comparison of ...113 transponder-InSAR observations with independent validation measurements (levelling or GPS) yields a transponder precision range of 1.8-4.6 mm after outlier removal for double-difference (spatial and temporal) phase measurements in the satellite line of sight for Envisat and ERS-2, making it a compact and lightweight alternative to a corner reflector for C-band InSAR.
Artificially introduced persistent scatterers (PS) are often desirable, and sometimes even crucial, when monitoring deformation using InSAR especially in non-urbanised areas. The use of active radar ...transponders as viable `artificial PS' is demonstrated via two field experiments: a validation test in a controlled calibration environment, and their operational use for monitoring landslides. In the latter case, the added value of having collocated InSAR-GNSS measurements is also presented.
Cottonseed is a sustainable source of plant protein, producing ~10 million metric tons of protein globally. This protein has the potential to fulfil the annual protein requirement of more than half a ...billion people globally. Its functional properties have established the potential of cottonseed protein (CSP) as a candidate for alleviating malnutrition in the Asian and African continents. Regardless of these quality attributes, the inherent association of gossypol with CSP makes it unsuitable for direct human consumption due to its toxicity.
The present review elaborates on physical, chemical and biological methods for enhancing the quality and suitability of CSP for human nutrition by reducing the gossypol content to permissible limits (450 ppm) per the U.S. Food and Drug Administration and World Health Organization. Amino acid profiling, functional property (water holding capacity, oil holding capacity, foaming properties, emulsification characteristics, and protein solubility), in vitro protein digestibility and molecular weight analyses are the parameters considered important for the application of CSP in foods. This review also highlights the diverse applications of CSP directly in human nutrition or indirectly as animal protein.
Degossypolyzation is mainly performed by solvent extraction, although gamma irradiation and the use of microorganisms are gaining momentum. CSP is a good candidate for use in food and feed formulations, with a balanced amino acid composition and functional properties comparable to those of soy protein. Integration of both chemical and biological methods might prove to be more efficient for degossypolization and improving the utilization of CSP for human nutrition.
•Physical, chemical, and biological methods for improving utilization of cottonseed as protein source.•Solvent extraction remains the method of choice.•Functional properties and amino acid profile for evaluation of quality of cottonseed protein are well discussed.•Application of cottonseed protein as direct and indirect source of supplement in human nutrition.•Food safety and regulatory issues for application of cottonseed protein/flour in foods is outlined in the review.
PDF
