Principles and theory of radar interferometry september 19, 2004 igarss 04 tutorials paul a rosen. In this study, we developed the precise algorithm for phase to height conversion, including the ambiguity method taking into account earth ellipsoid, schw. Osa unscented information filtering phase unwrapping. Interferometric synthetic aperture radar insar is commonly used in earth sciences to study surface displacements or construct high resolution topogr. Data of this form are found in many applications, but the advent in the early 1990s of synthetic aperture radar interferometry in sar, in particular, spurred interest in developing reli. Phase unwrapping algorithms share a common initial approach. The commercial availability of these algorithms is leading to wide spread application in the user community. Phase unwrapping rocca 5 the technique shown is successful provided that the true gradient is bounded to.
A method for acquiring mutually orthogonal interference signal is introduced. In twodimensional phase unwrapping, two internationally recognized experts sort through the multitude of ideas and. Multibaseline sar interferometry for automatic dem. At the beginning of the studies on sar interferometry 198889, the phase unwrapping problem was investigated assuming that only two sar images were available. The proposed algorithm is the result of combining an unscented information filter with a levenbergmarquardt method, a robust phase gradient estimator called the amended matrix pencil model, and an efficient qualityguided strategy based on heapsort.
Phase unwrapping of multibaseline interferometry using. Phase unwrapping is the process of recovering unambiguous phase values from phase data that are measured modulo 2. Next, we give a brief overview of the phase unwrapping problem. Improvements are presented in order to use this method in areas with intensely fluctuated fringe lines. The development of satellite technology is rapidly increasing the evolution of remote sensing.
Two practicable methods are proposed based on the greens first identify with properly chosen greens functions satisfying the imposed newmanns boundary conditions. We also use the pseudointerferogram to reduce the phase aliasing. Thus a phase unwrapping has to be carried out to obtain the absolute phase, which finally can be transformed to the desired height z at each point over the xyarea leading to a three. However, problems such as accuracy and speed of phase unwrapping process still remain a challenge for sar interferometry.
Often such interferograms are used to observe land surface deformation in the order of centimeters over long time intervals, say up to years. Osa fast phase unwrapping algorithm for interferometric. An approach to twodimensional 2d phase unwrapping for synthetic aperture radar sar interferometry is presented, based on separate steps of coarse phase and fine phase estimation. This paper proposes a new phase unwrapping pu algorithm based on an unscented information filter for interferometric fringes. Pdf phase unwrapping is the key problem in building the digital elevation model dem of a scene from interferometric synthetic aperture radar sar. All these algorithms begin with the measured gradient of the phase field, which is subsequently integrated to recover the unwrapped phases. Section v shows simulations of 2d phase unwrapping by comparing the theory and methods for if estimation with the results of lms unwrapping. Insarinterferometric synthetic aperture radar has been studied and used. This paper discusses a phase unwrapping algorithm based on fringe line detection. Sar based threedimensional mapping is very helpful tool to understand largearea fault mechanism and following secondary surface deformation. Joint phase unwrapping for multifrequency sar interferometry. Compared with the traditional singlebaseline sb pu, mb pu is applicable to.
Satellite images give extensive useful information about the land structure that is easily manageable in the process of generating true, highspeed information which allows the forecasting of future environmental and urban planning. One of the factors critical to mapping accuracy is phase unwrapping. Multibaseline sar interferometry for automatic dem reconstruction. A \lake model, which simulates an uncorrelated sar. Remote sensing comprises active and passive systems. One of the most challenging aspects in the successful application of sar interferometry insar is unwrapping the interferometric phase. We are presenting a new method to unwrap the phase from irregularly sampled differential sar interferograms.
Twodimensional 2d phase unwrapping has received a great deal of attention in recent years, owing in large part to the advent of synthetic aperture radar sar interferometry. Two complementary inflection point retrieval methods are summarized. In this application, multiple coherent radar images of the same area are combined to form interferograms, with the 2d interferometric phase arrays. A novel phasebased approach to tear film surface quality. Sentinel1 insar phase unwrapping using s1tbx and snaphu. We present an algorithm that solves the phase unwrapping problem, using a combination of fourier techniques. Phase unwrapping for sar interferometry a data fusion. A helpful useful resource like no totally differentthe first full info to half unwrapping. Twodimensional phase unwrapping by ghiglia, dennis c. Phase unwrapping in three dimensions with application to insar.
This part of the insar principles manual is dedicated to beginners who. While phase unwrapping algorithms have proliferated over the past 10 years, two main approaches are currently in use. Refined twostage programmingbased multibaseline phase. National aeronautics and space administration applied remote sensing training program 2. Using interference data of esa ers1 satellite to do experiments, it show that this method is superior to least squares method, quality guided method and original kalman filter method in unwrapping precision and quality, it has higher stability. The phase of the sar image is determined primarily by the distance between the. The paper addresses the problem of the development of robust algorithms for unwrapping the interferometric phase if produced in the sar interferometry. Singlepass crosstrack interferometry with rerrasarx tandem. Sar, in particular, spurred interest in developing reli able twodimensional 2d phase unwrapping. Pdf multiresolution phase unwrapping for sar interferometry. Differential sar interferometry for land subsidence monitoring. Note that when performing the multilook process for data that will be used for phase unwrapping, the coherence band coh must be included along with the i and q bands. Results on x sar interferometric data are obtained.
Insar, kalman filtering, phase unwrapping, sar interferometry. We investigate a multimodel approach to deal with phase. An analysis of the calibration of angle difference in dual. Pdf phase unwrapping for interferometric sar using. The amplitude is the strength of the radar response and the phase is the fraction of one complete sine wave cycle a single sar wavelength. In all cases the problem is that the measuredphase signal can only take on values in a range, whilst the original phase signal can take on any value. Phase unwrapping is the most complicated stage of interferometric data processing. Two image pairs and no motion in one of them with two interferometric pairs four sar images and no terrain motion in one of them. An overview of sar interferometry esa earth observation data.
That was the actual situation at that time since the only few interferometric sar images were from the seasat and the jpl single pass airborne systems. Finally, extended kalman filter smooth reduce the errors spread. The interferometric phase is ambiguous and only known within 2. Phase unwrapping of low coherence differential interferograms.
Mapping secondary surface deformation related to the 2018. Phase unwrapping for sar interferometry a data fusion approach by kalman filtering. Interferometric synthetic aperture radar phase unwrapping based on. Extended kalman filter phase unwrapping smooth algorithm in. A fast phase unwrapping algorithm for sar interferometry. Phase unwrapping in sar interferometry consists of two steps. Interferometric synthetic aperture radar presents a new technology for performing highresolution topographic mapping. The information coming from several interferograms with different baselines increases the elevation ambiguity interval and allows automatic phase unwrapping. Twodimensional phase unwrapping with use of statistical.
Digital elevation model dem generation using the sar. Principles and theory of radar interferometry september 19, 2004 igarss 04 tutorials paul a rosen jet propulsion laboratory ieee is an authorized ceu provider of the international association for continuing education and training. Osa phase unwrapping through fringeline detection in. If the data are good, phase unwrapping is straigh orward. Phase unwrapping a discussion is given first of 2d phase unwrapping as an. Multibaseline sar interferometry can be successfully exploited for automatic phase unwrapping and high quality digital elevation model dem reconstruction. A polarimetric approach s guillaso, l ferrofamil, a reigber, e pottier university of rennes i, france. In this recipe, we will use snaphu, which is a twodimensional phase. The phase diagram clari es that phase unwrapping is accurately. X sar desa champ system and mission heritage srtm tandemx terrasarx topas grace tandemx. Two laws used for acquiring the preliminary conversion signal are summarized. The execution time for our algorithm is equivalent to the computation time required for performing. Given an input interferogram and other observable data, snaphu attempts to compute congruent phase unwrapped solutions that are maximally probable in an. Application synthetic aperture radar, general optical interferometry, mr angiography, mr chemical.
In this study, we mapped surface displacements caused by the 2018 sulawesi earthquakes in threedimension. The software is publicly available and should run on most unixlinux platforms. Wavelength scanning distance interferometry using inflection. This unambiguous phase can then be used for the computation of the scene height model. The insar interferometric sar processing steps for dem generation consist of the coregistration of two sar data, interferogram generation, phase filtering, phase unwrapping, phase to height conversion, and geocoding, etc.
The advent of interferometric sar for geophysical studies, in particular, has resulted in the need for accurate, ef. Radio science, volume 23, number 4, pages 7720, julyaugust 1988 satellite radar interferometry twodimensional phase unwrapping richard m. In this recipe, we will use snaphu, which is a twodimensional phase unwrapping algorithm developed by chen and zebker. We consider phase images as a sequence of measurements and apply 3d kalman filtering to effectively combine those measurements. However, problems such as accuracy and speed of phase unwrapping process still remain a challenge for sar interferometry applications. This tutorial walks through an example of stripmap interferometry on the 2014 napa valley earthquake. Data of this form are found in many applications, but the advent in the early 1990s of synthetic aperture radar interferometry in sar. Each is most useful only for certain restricted applications. The various phase unwrapping algorithms differ in the way these two steps are done. Processing strategies for phase unwrapping for insar applications charles l.
Geometric aspects of interferometric phase measurement a. Most of these phase unwrapping techniques are suitable for a phase unwrapping for a static fringe system generated by interferometry, however when we have to generate phase. Request pdf phase unwrapping for sar interferometry a data fusion approach by kalman filtering this paper considers the problem of unwrapping the phase image obtained from a noisy. Interferometric synthetic aperture radar, abbreviated insar or deprecated ifsar, is a radar technique used in geodesy and remote sensing. Thus a phase unwrapping has to be carried out to obtain the absolute phase, which. An insar phase unwrapping algorithm with the phase. In this chapter, we propose a modi ed ltering algorithm to the l opez and fabregas l. In this paper we present a new phase unwrapping method for multiple interferometric sar measurements, which is based on kalman filtering.
To date all algorithms applied to interferometric sar have used variations of. Technical university of berlin, germany introduction phase unwrapping in sar interferometry is a key step to construct a topographic map from a sar dataset. Phase unwrapping algorithms for radar interferometry. For optimal unwrapping results it is recommended to multilook and phase filter the interferogram, as instructed in the insar data recipe. Phase unwrapping is a mathematical disadvantagefixing technique extra and extra utilized in synthetic aperture radar sar interferometry, optical interferometry, adaptive optics, and medical imaging. In twodimensional phase unwrapping, two internationally recognized experts sort through the multitude of ideas and algorithms. Thermodynamicsinspired phase unwrapping in remote sensing. The tutorial covers creating subsets, coregistration, spectral filtering, interferogram formation, coherence estimation, topographic phase removal, phase filtering, phase unwrapping. Interferometric synthetic aperture radar phase unwrapping based on sparse markov random fields. Robust algorithms for phase unwrapping in sar interferometry. A wide range of interferometric techniques recover phase information that is mathematically wrapped on the interval. A sar signal contains amplitude and phase information. Guidelines for sar interferometry processing and interpretation.
Traditionally, interferograms were measured by locating the center of a fringe and then tracing along the fringe. Phase shifting interferometry avoids the need to track. A wavelength scanning distance interferometry scheme is demonstrated. A resource like no otherthe first comprehensive guide to phase unwrapping phase unwrapping is a mathematical problemsolving technique increasingly used in synthetic aperture radar sar interferometry, optical interferometry, adaptive optics, and medical imaging.
From the measured, wrapped phase, unwrap the phase from some arbitrary starting location, then. A new method for temporal phase unwrapping of persistent. Various phase unwrapping algorithms have been developed for extraction of topographic digital terrain model dtm and displacement detection in sar interferometry since 1988. Obtaining the true unwrapped phase is a longstanding problem. We propose an efficient algorithm, named corphu correction of phase unwrapping errors, for the correction of unwrapping errors after phase unwrapping, based on the phase closure of interferogram triplets within an interferometric network. A fast, automated, ndimensional phase unwrapping algorithm. Phase unwrapping in three dimensions with application to.
Pdf development of unwrapped insar phase to height. A comparison of phase unwrapping techniques in synthetic. This geodetic method uses two or more synthetic aperture radar sar images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite or aircraft. Phase unwrapping is a problem that occurs in several. The insar multilooked phase is described by the following pdf.
Multibaseline mb phase unwrapping pu is a key step of mb synthetic aperture radar sar interferometry insar. The difficulties arise in attempting to find global optimization procedures with the. Phase unwrapping is the key problem in building the elevation map of a scene from interferometric synthetic aperture radar sar system data. This paper presents a new algorithm that unwraps phase through fringeline detection. Synthetic aperture radar sar interferometry insar is primarily used in remotesensing applications and has created a new class of radar data that has significantly evolved during the last couple of decades. Phase unwrapping consists in the reconstruction of the phase difference of the radiation received by two sar systems as a function of the azimuth and slant range coordinates. They confirm the excellent performance of the procedure. Index termsinterferometric synthetic aperture radar.
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