High precision measurement on the absolute localization accuracy of TerraSAR-X

Balss, Ulrich; Cong, Xiaoying; Brcic, Ramon; Minet, Christian; Breit, Helko; Eineder, Michael; Fritz, Thomas

doi:10.1109/igarss.2012.6351217

Cited by 27 publications

(36 citation statements)

References 3 publications

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“…1 Mainly depending on CR size (1.5 or 0.7 m) and imaging mode (ST300 or HS300). 2 Depending on test site and incidence angle. 3 Conservative assumption.…”

Section: Analysis Of Error Contributionsmentioning

confidence: 99%

“…However, SAR offers several additional capabilities. The objective of this paper is to highlight the ability to provide also absolute localization accuracy of bright, well-detectable radar targets at centimeter level [1][2][3][4] with respect to a given geodetic reference frame like International Terrestrial Reference Frame, release 2014 (ITRF2014) [5]. Such a high accuracy-where TerraSAR-X/TanDEM-X lead worldwide among space borne SAR sensors [6]-can be achieved only if the SAR data are processed and calibrated with meticulous care and if they are corrected for well-known effects such as wave propagation and solid Earth dynamics, as it is done in geodesy [7].…”

Section: Introductionmentioning

confidence: 99%

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Measurements on the Absolute 2-D and 3-D Localization Accuracy of TerraSAR-X

Balss¹,

Gisinger²,

Eineder³

2018

Remote Sensing

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Abstract:The German TerraSAR-X radar satellites TSX-1 and TDX-1 are well-regarded for their unprecedented geolocation accuracy. However, to access their full potential, Synthetic Aperture Radar (SAR)-based location measurements have to be carefully corrected for effects that are well-known in the area of geodesy but were previously often neglected in the area of SAR, such as wave propagation and Earth dynamics. Our measurements indicate that in this way, when SAR is handled as a geodetic measurement instrument, absolute localization accuracy at better than centimeter level with respect to a given geodetic reference frame is obtained in 2-D and, when using stereo SAR techniques, also in 3-D. The TerraSAR-X measurement results presented in this study are based on a network of three globally distributed geodetic observatories. Each is equipped with one or two trihedral corner reflectors with accurately (<5 mm) known reference coordinates, used as a reference for the verification of the SAR measured coordinates. Because these observatories are located in distant parts of the world, they give us evidence on the worldwide reproducibility of the obtained results. In this paper we report the achieved results of measurements performed over 6 1/2 years (from July 2011 to January 2018) and refer to some first new application areas for geodetic SAR.

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“…1 Mainly depending on CR size (1.5 or 0.7 m) and imaging mode (ST300 or HS300). 2 Depending on test site and incidence angle. 3 Conservative assumption.…”

Section: Analysis Of Error Contributionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Measurements on the Absolute 2-D and 3-D Localization Accuracy of TerraSAR-X

Balss¹,

Gisinger²,

Eineder³

2018

Remote Sensing

Self Cite

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“…The measurement series on hand is based on a CR with very precisely known ground coordinates (better than 5 millimeters) which we installed near the geodetic observatory Wettzell, Germany [3] [4]. Up to now, 52 high resolution Spotlight (HS) datatakes were recorded in two different acquisition geometries.…”

Section: Experimental Verificationmentioning

confidence: 99%

“…Previous studies showed a ranging accuracy at the centimeter level [1][2][3][4]. This accuracy level becomes attainable by a thorough design of all subsystems, including the precise orbit determination [5] [6], and the elimination of several processor approximations in the SAR data processing [4].…”

Section: Introductionmentioning

confidence: 99%

“…Thus, very precise knowledge of the underlying clock rate and of possible timing offsets is one critical prerequisite for precise position measurements by SAR. Beyond that, as the conversion from travel time to geometric distance usually refers to the vacuum velocity of light, the travel time has to be compensated for all signal propagation delays as we already detailed in our former papers [3][4].…”

Section: Introductionmentioning

confidence: 99%

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Analysis of internal timings and clock rates of TerraSAR-X

Balss

Breit

Fritz

et al. 2014

2014 IEEE Geoscience and Remote Sensing Symposium

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Due to the indirect measurement principle of radar on base of signal travel time, a very precise calibration of the sensor's internal clock with regard to clock rate and potential time offsets relative to the Coordinated Universal Time is an essential prerequisite for accurate pixel localization in Synthetic Aperture Radar. Giving special considerations on this aspect, we developed two algorithms that improve the already high localization accuracy of TerraSAR-X: The either one very precisely determines the true oscillator clock rate, while the other one effectively refines the accuracy of time annotation. Experimental analyses evaluate the obtained improvements in localization accuracy from both techniques.

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High-precision positioning of radar scatterers

Dheenathayalan

Small

Schubert

et al. 2016

J Geod

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Remote sensing radar satellites cover wide areas and provide spatially dense measurements, with millions of scatterers. Knowledge of the precise position of each radar scatterer is essential to identify the corresponding object and interpret the estimated deformation. The absolute position accuracy of synthetic aperture radar (SAR) scatterers in a 2D radar coordinate system, after compensating for atmosphere and tidal effects, is in the order of centimeters for TerraSAR-X (TSX) spotlight images. However, the absolute positioning in 3D and its quality description are not well known. Here, we exploit time-series interferometric SAR to enhance the positioning capability in three dimensions. The 3D positioning precision is parameterized by a variance-covariance matrix and visualized as an error ellipsoid centered at the estimated position. The intersection of the error ellipsoid with objects in the field is exploited to link radar scatterers to real-world objects. We demonstrate the estimation of scatterer position and its quality using 20 months of TSX stripmap acquisitions over Delft, the Netherlands. Using trihedral corner reflectors (CR) for validation, the accuracy of absolute positioning in 2D is about 7 cm. In 3D, an absolute accuracy of up to B Prabu Dheenathayalan ∼66 cm is realized, with a cigar-shaped error ellipsoid having centimeter precision in azimuth and range dimensions, and elongated in cross-range dimension with a precision in the order of meters (the ratio of the ellipsoid axis lengths is 1/3/213, respectively). The CR absolute 3D position, along with the associated error ellipsoid, is found to be accurate and agree with the ground truth position at a 99 % confidence level. For other non-CR coherent scatterers, the error ellipsoid concept is validated using 3D building models. In both cases, the error ellipsoid not only serves as a quality descriptor, but can also help to associate radar scatterers to real-world objects.

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High precision measurement on the absolute localization accuracy of TerraSAR-X

Cited by 27 publications

References 3 publications

Measurements on the Absolute 2-D and 3-D Localization Accuracy of TerraSAR-X

Measurements on the Absolute 2-D and 3-D Localization Accuracy of TerraSAR-X

Analysis of internal timings and clock rates of TerraSAR-X

High-precision positioning of radar scatterers

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