Abstract
There are two useful methods of current measurement based on synthetic aperture radar (SAR): one is along-track interferometry (ATI), and the other is Doppler centroid analysis (DCA). For the ATI method, the interferometric phase must be accurate enough for ocean current measurements. Therefore, the space-varying of phase imbalances along the range, caused by antenna phase center position error, attitude error, antenna electronic miss pointing, antenna pattern mismatch, and other reasons, cannot be ignored. Firstly, this paper mainly analyzes the above possible factors by using real GF-3 ATI data and error model simulation results. Secondly, the ocean current has been preliminarily measured by the ATI method and the DCA method, using CDOP model, based on the GF-3 ATI data of the ocean scene near Qingdao, China, which is up to around −1.45 m/s. The results of the two methods are in good agreement with the correlation coefficient of 0.98, the mean difference of −0.010 m/s, and the root mean squared error (RMSE) of 0.062 m/s. Moreover, by comparing with the current measured by high-frequency surface wave radar (HFSWR), the correctness of the analysis is further proved.
Highlights
The study of ocean currents is an important part of ocean dynamics and is of great significance to humans working on the sea and in coastal areas
The CDOP model is obtained by using a three-layer neural network training the Doppler frequency shift of ASAR data and the wind retrieved by ASCAT; whether it is suitable for GF-3 data needs further verification
GF-3 along-track interferometry (ATI) mode performs imaging through dual-receive fine stripmap mode, which has an effective along-track antenna separation of 3.75 m
Summary
The study of ocean currents is an important part of ocean dynamics and is of great significance to humans working on the sea and in coastal areas. Synthetic aperture radar (SAR) is a high-resolution imaging radar that can observe the Earth for all weather and all time. Since the first spaceborne SAR, SeaSat, was launched successfully in 1970, SAR has shown irreplaceable ocean observation advantages. SAR can accurately measure ocean currents with high spatial resolution. Two methods of SAR current measurement are produced based on the characteristic that a target moving relative to the radar will make a Doppler frequency shift proportional to the speed. Goldstein and Zebker [1,2] proposed the concept and basic theory of ocean currents obtained by ATI-SAR in 1987 and demonstrated for the first time the ability of ATI-SAR to measure surface currents in San Francisco Bay, Mission Bay, and San Diego Bay in 1989. Frasier [3] combined the in site acoustic Doppler current profiler (ADCP)
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