One of the gmti techniques currently being explored is based on sar along track interferometry sar ati, which uses the magnitudephase information of the interferogram to extract movers from stationary clutter. Demonstration of current measurements from space by along. Track interferometry single, stationary antenna moving target no interferometric baseline. By having antennas separated in the along track direction interferometry provides a very sensitive measure of the lineofsight velocity. Alongtrack synthetic aperture radar sar interferometry is a remote sensing technique capable. This method can measure the along track displacement with a measurement accuracy of. Motion detection using tandemx alongtrack interferometry. Pdf along track interferometry synthetic aperture radar atisar.
Abstract in this paper we consider the detection of a moving point target using along track at insar systems. Alongtrack interferometry system geometry suppose that the two antennas are mounted on the same aircraft, so that h. The doppler centroid analysis cannot be expected to deliver as accurate results as along track interferometry with optimal system parameters, but it has the unique advantage that it can be applied to the raw data of any newly acquired or a rchived singleantenna sar image without any special preparations 9. The empirical accuracies of the mai measurements are about 6. Crosstrack resolution achieved by short or coded pulses. Radar interferometry and its application to changes in the.
By mapping a targets signal onto a fractional fourier axis, the frft permits a constantvelocity target to be focused in the fractional fourier domain thereby affording orders of magnitude. Sar alongtrack interferometry with application to radarsat2. Ocean currents and ship velocities can be measured using along track interferometry. Alongtrack interferometric synthetic aperture radar nec. Bamler german aerospace center dlr, oberpfaffenhofen, d. Direct surface current field imaging from space by along. The flight direction of the platform carrying the along track antennas is in thex direction and these two antennas are separated by a distance b remote sensing of ocean waves and currents using airsar alongtrack interferometry ati.
River run off measurement with sar along track interferometry. Theoretical accuracy of alongtrack displacement measurements. Radar interferometry and its application to changes in the earths surface didier massonnet department of radar systems performance centre national detudes spatiales. Traffic monitoring using srtm along track interferometry, in to submit an. One of the gmti techniques currently being explored is based on sar alongtrack interferometry sar ati, which uses the magnitudephase information of the interferogram to extract movers from stationary clutter.
The performance of the system is evaluated by comparing the. The multiple channel antennas of the radar are assembled at. Ship detection and motion parameter estimation with. Traffic monitoring using srtm alongtrack interferometry h. Timedomain simulation of alongtrack interferometric sar for. Moving target detection by alongtrack interferometry. A relatively unknown yet powerful technique, the socalled fractional fourier transform frft, is applied to sar along track interferometry sarati in order to estimate moving target parameters. Consequently, the precise measurement of the along track displacement is a key issue in measuring the 3d displacements from insar method.
Measurement of slowmoving alongtrack displacement from an. Exploring the benefits of using cryosat2s cross track. We concentrate on two clutter cancelation methods known as the displaced phase center antenna dpca technique and along track sar interferometry. Across track interferometry as a measurement of angle. The observables measured by an interferometer are fringe visibility and closure phase, which can then be tted by a model or used to reconstruct an. Conventional along track interferometric synthetic aperture radar, atisar, approaches can detect targets with very low radial speeds, but their false alarm rate is too high to be used in ground moving target indication radars. Along track interferometry uses multiple receive antennas separated in the along track dimension in order to extract information about target motion in the imaged scene. Along track interferometry tandemx satellite data for. The mode allows two sar images to be taken under identical geometry of observation, but separated by a short time lag. Spaceborne alongtrack sar interferometry uzh department of.
Along track interferometric synthetic aperture radar atinsar systems are used to estimate the radial velocity of targets moving on the ground, starting from the interferometric phases, obtained by the combinations of two complex sar images acquired by two antennas spatially separated along the platform moving direction. Introduction along track interferometry ati is an operational and easy way in ground moving target indication gmti with along track dualreceived 15 january 2012, accepted 15 may 2012, scheduled 27 may 2012 corresponding author. The method to combine along track interferometry ati and constant false alarm rate cfar detection, referred to as aticfar, is considered to be a promising method for ground moving target indication gmti. Since then, the feasibility of current measurements by this technique has been demonstrated in a number of further experiments, using interferometric sar insar systems on aircraft e. In absence of targets, the pdf of the interferometric phase can be expressed in. Sentinel1 tops interferometry for alongtrack displacement measurement article pdf available in iop conference series earth and environmental science 571.
All existing examples of current measurements by spaceborne synthetic aperture radar sar along track interferometry atihave suffered from short baselines and corresponding low sensitivities. The performance of the presented along track interferometric system is evaluated by comparing the probability of false alarm and the probability of detection obtained in the two cases. A substantial improvement in measuring the along track displacement has been made with the multiple aperture sar interferometry mai proposed by bechor and zebker 15. Ocean surface feature detection with the ccrs alongtrack. Ship detection and motion parameter estimation with tandemx. Gmti for squint looking xtisar with rotatable forward. All motion measured via ati are components of the velocity along the look vector. Quality assessment of surface current fields from terrasar. Introduction the german xband radar satellite terrasarx will be launched in 2006.
Alongtrack interferometric synthetic aperture radar atinsar systems are. Index terms tandemx, alongtrack interferometry, traffic measurement, surface current estimation 1. Along track interferometry synthetic aperture radar atisar. Pdf synthetic aperture radar interferometry researchgate. Mti methods including alongtrack interferometry ati and displaced phase. Tidal current measurement with terrasarx alongtrack interferometry steffen suchandt 1, hartmut runge 1, roland romeiser 2, nuria tousramon 1, ulrich steinbrecher 1 1german aerospace center dlr, d82234 wessling, germany. Use two antennas on moving platform to achieve time interval.
One of the gmti techniques, currently being explored, is based on sar along track interferometry sarati, which uses the magnitudephase information of the interferogram to extract movers from stationary clutter. Phase values outside interval wrap mod, so that such values are indistinguishable from the ones differing for multiples. The residual clutter has a negative impact on the performance of. In this paper the performance of each processor is examined for three radarsat2 slantrange resolutions. Jun 10, 2015 a timedomain simulation of along track interferometric synthetic aperture radar atinsar has been developed to support ocean observations. Research on moving target indication based on along track. The fundamental principle is that the interferometric combination of two complex sar images of the same scene, acquired with a short time lag, is sensitive to the. Application of fractional fourier transform to moving target. A comparison of displaced phase centre antenna and along track interferometry techniques for radarsat2 ground moving target indication. Sar data derived from a single observation are subjec.
All motion measured via ati are components of the velocity along. Measurement of slowmoving along track displacement from an ef. Direct surface current field imaging from space 3 2. This situation can be improved by implementing operational along track interferometry ati capabilities on future sar satellites. Ocean surface feature detection with the ccrs along track insar. In synthetic aperture radar sar, interferometry may be divided into two categories. Demonstration of current measurements from space by.
Introduction althoughbistatic sar bsar systemshave beenstudied for the rst time more than25 yearsago, theyhave. Pdf in february 2000, the shuttle radar topography mission srtm was flown as the first singlepass sar interferometer in space. Quality assessment of surface current fields from terrasarx. Pdf traffic monitoring using srtm alongtrack interferometry. The same holds for the corresponding radial velocity values. Ship detection and motion parameter estimation with tandemx in large along track baseline configuration stefan. Here, singlepass data is jointly processed from two or more receive channels which are spatially offset in the along track direction. In order to evaluate the ability of the method used for gmti with terrasarx data, a set of. The interferometric imaging modes of the tandemx\ud terrasarx addon for digital elevation measurements\ud satellite formation offer improved along track interferometric capabilities e. Sar along track interferometry with application to. Timedomain simulation of alongtrack interferometric sar. Current measurements by sar alongtrack interferometry from a. The along track interferometric phase depends on radial velocity, baseline, and wavelength as shown in.
In chapter 3 the formation control requirements for alongtrack oceanographic interferometry are derived. The available products relevant for interferometry are presented and other relevant topics like orbit control and deltak interferometry are discussed. Remote sensing of ocean waves and currents using airsar. Measurement of slowmoving alongtrack displacement from. The paper summarizes the need for global space borne river runoff measurements. Alongtrack interferometry by onebitcoded sar signals. Introduction sar along track interferometry permits the detection and. Terrasarx tandemx alongtrack interferometry ati baseline in the order of 1 m transmit receive b ati,eff 1. A comparison of displaced phase centre antenna and along. A timedomain simulation of alongtrack interferometric synthetic aperture radar atinsar has been developed to support ocean observations. However, the estimated empirical accuracies cannot be generalized to any interferometric pair because they largely depend on the processing parameters and coherence of.
Along track interferometry ati from syntheticaperture radar sar is a promising new technique for measuring and mapping the spatial structure of ocean surface velocities. Bedding school of physics, university of sydney 2006, australia abstract. Alongtrack interferometry for simultaneous sar and gmti. Theoretically, the best data quality at x band is expected at effective baselines on the order of 30 m, i. First results of tandemx alongtrack interferometry core. In contrast to the coarse 200 m alongtrack accuracy required for routine acrosstrack interferometric global dem acquisition, the alongtrack separation desired for ati oceanography is only 50 m 10 m. Mar, 2003 canadas radarsat2 r2 synthetic aperture radar sar satellite will be equipped with an experimental ground moving target indication gmti mode, which makes use of the dualreceive capability of the r2 antenna to provide two apertures aligned in the along track direction. Multichannel alongtrack interferometric sar systems. The fundamental principle is that the interferometric combination of two complex sar images of the same scene. Conventional along track interferometric synthetic aperture radar, atisar, approaches can detect targets with very low radial speeds, but their false alarm rate.
Scansar trades resolution in along track dimension for swath. On the retrieval of total surface current using dual. Ship detection and motion parameter estimation with tandemx in large alongtrack baseline configuration stefan. The ati technique permits direct velocity measurements with spatial resolutions on the order of 100 m, which would be attractive for many applications. Acrosstrack interferometry as a measurement of angle. Bistatic sar along track interferometry with multiple fixed receivers sergi duque 1,pacolopezdekker. Introduction canadas radarsat2 commercial sar satellite, to be launched in spring 2006, will have an experimental mode called modex for moving object detection experiment that will allow the full antenna to be broken into two sub. Abstractsea surface height ssh measurements provided by pulselimited radar altimeters are onedimensional profiles along the satellites nadir track, with no information whatsoever in. Conventional along track interferometric synthetic aperture radar, atisar, approaches can detect targets with very low radial speeds, but their false alarm rate is too high to be used in ground. Comparison of current fields from terrasarx and tandemx.
Sentinel1 tops interferometry for alongtrack displacement measurement view the table of contents for this issue, or go to the journal homepage for more 2017 iop conf. Conventional along track interferometric synthetic aperture radar, atisar, approaches can detect targets with very low radial speeds, but their false. With the standard helical orbit pattern, the two satellites have an along track distance between 0 at the northern and southernmost points of the orbit and about 550 m over the equator, limiting the region of useful along track baselines for intersatellite interferometry to narrow latitude bands far in. Measurement of slowmoving alongtrack displacement from an ef. Application of hybrid alongtrack interferometrydisplaced. Interferometry is a family of techniques in which waves, usually electromagnetic, are superimposed in order to extract information. Canadas radarsat2 r2 synthetic aperture radar sar satellite will be equipped with an experimental ground moving target indication gmti mode, which makes use of the dualreceive capability of the r2 antenna to provide two apertures aligned in the along track.
Along track interferometry observations along track interferometry ati from syntheticaperture radar sar is a promising new technique for measuring and mapping the spatial structure of ocean surface velocities. Moving target detection by along track interferometry. Pdf moving target detection by alongtrack interferometry. The results from two different sar techniques, including along track interferometry ati show good correspondence. While the geometrical alignment should in theory be suf. We must then sort out a collection of signals, each one of which is a mixture of a thousand 5m samples, each of which contributes to a. Demonstration of current measurements from space by alongtrack sar interferometry with srtm data roland romeiser1, helko breit2, michael eineder2, and hartmut runge2 1 institute of oceanography, university of hamburg, troplowitzstra. Performing organization names and addresses stiefvater consultants 2 hillside terrace marcy new york 403 8.
Along track interferometry synthetic aperture radar ati. Canadas radarsat2 r2 synthetic aperture radar sar satellite will be equipped with an experimental ground moving target indication gmti mode, which makes use of the dualreceive capability of the r2 antenna to provide two apertures aligned in the along track direction. The report proposed a dualthreshold approach that combines the conventional interferometric phase detection and the sar image amplitude. The simulation is in the time domain and based on bragg scattering to be applicable for moving ocean surfaces. The measurement of precise along track displacements has been made with the multipleaperture interferometry mai. To form an interferogram, the signals from the two chan. This tutorial gives a general introduction to optical and infrared interferometry. Introduction sar alongtrack interferometry permits the detection and. The flexibility of the tandemx interferometer and the high sensitivity to ground motions offer new possibilities for ground motion measurement by means of ati techniques a large ati baseline and high motion sensitivity enable the detection of even near along track motions. Aug 31, 1999 an along track interferometric sar synthetic aperture radar of the present invention includes a single sar line and observes a target only once.