Ocean current estimated from X-band radar sea surface images

Sea surface currents can be derived from X-band radar sea surface images. The basic theory is previously known. However, in practice, the current estimates may be deteriorated by several sources of error. Trials with real radar data previously indicated that some further research was required to obtain reasonable current estimates. A current measurement algorithm has been derived, which compensates for some of the errors. In addition, a novel current measurement algorithm has been derived, using a slightly different approach to the problem, which makes it possible to avoid several of the sources of errors. Signal analysis is used in combination with knowledge about the properties of the three-dimensional image spectrum. The algorithms are tested on real radar data and compared to simultaneous microwave dual-frequency measurements and wind measurements. In addition, the estimated currents are evaluated by comparing to values obtained from the tidal model. Finally, the sea surface current vector field is estimated, with a resolution of 256 m, to provide more detailed information about the current within the radar image, which constitutes an area of many square kilometers.