scholarly journals Robust, Model-Based External Calibration of Multi-Channel Airborne SAR Sensors Using Range Compressed Raw Data

2019 ◽  
Vol 11 (22) ◽  
pp. 2674 ◽  
Author(s):  
Marc Jäger ◽  
Rolf Scheiber ◽  
Andreas Reigber
Keyword(s):  
Beam Forming ◽  
Raw Data ◽  
Single Pass ◽  
Robust Model ◽  
Antenna Phase ◽  
Antenna Phase Center ◽  
Delay Variations ◽  
Airborne Sar ◽  
Interferometric Sar ◽  
Calibration Techniques

The paper describes a method for the accurate calibration of multi-channel SAR instruments, such as those required to support SAR polarimetry, single-pass interferometry and digital beam-forming (DBF), on the basis of dedicated SAR acquisitions containing reference targets with known properties. Unlike conventional approaches, the method is based entirely on the analysis of range-compressed raw data. It leverages the pulse-by-pulse analysis of amplitude, phase and delay variations observed within the range histories of reference targets to fully characterize and correct propagation direction dependent calibration issues such as those related to antenna pointing or antenna phase center positions. The fact that the approach does not require SAR image focusing in azimuth is especially relevant in the context of DBF, where individual channels need to be calibrated but are, by themselves, under-sampled. The calibration techniques presented are illustrated and validated using multi-channel polarimetric and single-pass interferometric SAR data acquired by DLR’s airborne F-SAR and DBFSAR instruments.

scholarly journals Estimation of absolute GNSS satellite antenna group delay variations based on those of absolute receiver antenna group delays

GPS Solutions ◽  
2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Susanne Beer ◽  
Lambert Wanninger ◽  
Anja Heßelbarth
Keyword(s):  
Group Delay ◽  
Observation Data ◽  
Satellite Antenna ◽  
Phase Measurements ◽  
Gps Satellites ◽  
Antenna Phase ◽  
Antenna Phase Center ◽  
Delay Variations ◽  
Phase Center Variations ◽  
Code Pseudorange

AbstractGNSS satellite and receiving antennas exhibit group delay variations (GDV), which affect code pseudorange measurements. Like antenna phase center variations, which affect phase measurements, they are frequency-dependent and vary with the direction of the transmitted and received signal. GNSS code observations contain the combined contributions of satellite and receiver antennas. If absolute GDV are available for the receiver antennas, absolute satellite GDV can be determined. In 2019, an extensive set of absolute receiver antenna GDV was published and, thus, it became feasible to estimate absolute satellite antenna GDV based on terrestrial observations. We used the absolute GDV of four selected receiver antenna types and observation data of globally distributed reference stations that employ these antenna types to determine absolute GDV for the GPS, GLONASS, Galileo, BeiDou, and QZSS satellite antennas. Besides BeiDou-2 satellites whose GDV are known to reach up to 1.5 m peak-to-peak, the GPS satellites show the largest GDV at frequencies L1 and L5 with up to 0.3 and 0.4 m peak-to-peak, respectively. They also show the largest satellite-to-satellite variations within a constellation. The GDV of GLONASS-M satellites reach up to 25 cm at frequency G1; Galileo satellites exhibit the largest GDV at frequency E6 with up to 20 cm; BeiDou-3 satellites show the largest GDV of around 15 cm at frequencies B1-2 and B3. Frequencies L2 of GPS IIIA, E1 of Galileo FOC, and B2a/B2b of BeiDou-3 satellites are the least affected. Their variations are below 10 cm.

INS/GNSS Integration with Account for Timing Skew and Displacement of GNSS Antenna. Experience of Practical Realization

2021 ◽  
Vol 29 (3) ◽  
pp. 52-68
Author(s):  
N.B. Vavilova ◽  
◽  
A.A. Golovan ◽  
A.V. Kozlov ◽  
I.A. Papusha ◽  
...  
Keyword(s):  
Spatial Separation ◽  
Measurement Unit ◽  
Complex Data ◽  
Navigation Systems ◽  
Inertial Navigation Systems ◽  
Positioning Systems ◽  
Global Positioning ◽  
Antenna Phase ◽  
Antenna Phase Center ◽  
Timing Skew

We examine two aspects specific to complex data fusion algorithms in integrated strapdown inertial navigation systems aided by global positioning systems, with their inherent spatial separation between the GNSS antenna phase center and the inertial measurement unit, as well as with the timing skew between their measurements. The first aspect refers to modifications of mathematical models used in INS/GNSS integration. The second one relates to our experience in their application in onboard airborne navigation algorithms developed by Moscow Institute of Electromechanics and Automatics.

Experimental Determination of DRW Antenna Phase Center at mm-Wavelengths Using a Planar Scanner: Comparison of Different Methods

2011 ◽  
Vol 59 (8) ◽  
pp. 2806-2812 ◽  
Author(s):  
Pablo Padilla ◽  
Patrik Pousi ◽  
Aleksi Tamminen ◽  
Juha Mallat ◽  
Juha Ala-Laurinaho ◽  
...  
Keyword(s):  
Experimental Determination ◽  
Phase Center ◽  
Antenna Phase ◽  
Antenna Phase Center

scholarly journals Evaluation of Atmospheric Effects on Interferograms Using DEM Errors of Fixed Ground Points

Sensors ◽  
2018 ◽  
Vol 18 (7) ◽  
pp. 2336 ◽  
Author(s):  
Takashi Nonaka ◽  
Tomohito Asaka ◽  
Keishi Iwashita
Keyword(s):  
Phase Noise ◽  
Atmospheric Effects ◽  
Sar Images ◽  
Single Pass ◽  
Digital Elevation ◽  
Total Phase ◽  
Disaster Monitoring ◽  
The Difference ◽  
Elevation Model ◽  
Interferometric Sar

High-resolution synthetic aperture radar (SAR) data are widely used for disaster monitoring. To extract damaged areas automatically, it is essential to understand the relationships among the sensor specifications, acquisition conditions, and land cover. Our previous studies developed a method for estimating the phase noise of interferograms using several pairs of TerraSAR-X series (TerraSAR-X and TanDEM-X) datasets. Atmospheric disturbance data are also necessary to interpret the interferograms; therefore, the purpose of this study is to estimate the atmospheric effects by focusing on the difference in digital elevation model (DEM) errors between repeat-pass (two interferometric SAR images acquired at different times) and single-pass (two interferometric SAR images acquired simultaneously) interferometry. Single-pass DEM errors are reduced due to the lack of temporal decorrelation and atmospheric disturbances. At a study site in the city of Tsukuba, a quantitative analysis of DEM errors at fixed ground objects shows that the atmospheric effects are estimated to contribute 75% to 80% of the total phase noise in interferograms.

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