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Open AccessArticle

Calibration of an Airborne Interferometric Radar Altimeter over the Qingdao Coast Sea, China

1
Marine Survey Research Center, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China
2
Qingdao National Laboratory for Marine Science and Technology, Qingdao 266373, China
3
Laboratory for Ocean and Climate Dynamics, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China
4
Center for Ocean Mega-Science and Technology, Chinese Academy of Sciences, Qingdao 266071, China
5
College of Geodesy and Geomatics, Shandong University of Science and Technology, Qingdao 266590, China
6
Beijing Institute of Radio Measurement, Beijing 100854, China
7
College of Information Science and Engineering, Ocean University of China, Qingdao 266100, China
8
Geodetic Data Processing Centre of Ministry of Natural Resources, Xi’an 710000, China
9
Geodesy and Geomatics Engineering Laboratory, Technical University of Crete, GR-73100 Chania, Greece
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Remote Sens. 2020, 12(10), 1651; https://doi.org/10.3390/rs12101651
Received: 4 April 2020 / Revised: 13 May 2020 / Accepted: 16 May 2020 / Published: 21 May 2020
(This article belongs to the Special Issue Calibration and Validation of Satellite Altimetry)
Calibration/Validation (Cal/Val) of satellite altimeters is fundamental for monitoring onboard sensor performance and ensuring long-term data quality. As altimeter technology has been evolving rapidly from profile to wide swath and interferometric altimetry, different requirements regarding Cal/Val have emerged. Most current Cal/Val technology has been developed for conventional profile altimeters, whereby satellite observations are compared against measurements at one point along orbit lines. However, the application of this type of Cal/Val technique to swath interferometric altimeters with two-dimensional measurements is difficult. Here, we propose a new strategy for the evaluation of interferometric altimeters based on comparison of wave-induced sea surface elevation (WSSE) spectra from one- and two-dimensional measurements. This method assumes that the WSSE variance of an equilibrium wave field is uniform and can be measured equivalently in the space or time domains. The method was first tested with simulated data and then used to evaluate the performance of an airborne interferometric radar altimeter system (AIRAS) using Global Navigation Satellite System (GNSS) buoy measurements. The differences between the WSSE variances from the AIRAS and two GNSS buoys were below 8 cm2, corresponding to a standard deviation of 2.8 cm, which could serve as a reference for the WSSE error over the scale range of waves. The correlation coefficient between the AIRAS and GNSS buoys was approximately 0.90, indicating that the error was small relative to the WSSE signals. In addition, the sea surface height (SSH) difference measured by the AIRAS was compared with that derived from the GNSS buoys at two sites. The results indicated that the error of the SSH difference was 3 cm. This approach represents a possible technique for the Cal/Val of future spaceborne/airborne interferometric altimeters; however, additional experiments and applications are needed to verify the feasibility of this method. View Full-Text
Keywords: interferometric altimeter; Guanlan; GNSS buoy; power spectrum density; wavenumber; calibration; validation interferometric altimeter; Guanlan; GNSS buoy; power spectrum density; wavenumber; calibration; validation
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MDPI and ACS Style

Yang, L.; Xu, Y.; Zhou, X.; Zhu, L.; Jiang, Q.; Sun, H.; Chen, G.; Wang, P.; Mertikas, S.P.; Fu, Y.; Tang, Q.; Yu, F. Calibration of an Airborne Interferometric Radar Altimeter over the Qingdao Coast Sea, China. Remote Sens. 2020, 12, 1651.

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