Automatic Water Eddy Detection in SST Maps Using Random Ellipse Fitting and Vectorial Fields for Image Segmentation

The impact of water eddies off the Iberian coast in the chemistry and biology of the ocean ecosystems, on the circulation of ocean waters and on climate still needs to be studied. The task of identifying water eddies in sea surface temperature maps (SST) is time-consuming for oceanographers due to the large number of SST available. This motivates the present investigation aiming to develop an automatic system capable of performing that task. The system developed consists of a pre-processing stage where a vectorial field is calculated using an optical flow algorithm with one SST map and a matrix of zeros for input. Next, a binary image of the modulus of the vectorial field is created using an iterative thresholding algorithm. Finally, five edge points of the binary image, classified according to their gradient vector direction, are randomly selected and an ellipse corresponding to a water eddy fitted to them.

[1]  Euijin Kim,et al.  Fast and Robust Ellipse Extraction from Complicated Images , 2002 .

[2]  R. Halír.  Numerically Stable Direct Least Squares Fitting of Ellipses , 1998 .

[3]  Bahram Parvin,et al.  Singular features in sea surface temperature data , 2000, Proceedings 15th International Conference on Pattern Recognition. ICPR-2000.

[4]  David J. Fleet,et al.  Performance of optical flow techniques , 1994, International Journal of Computer Vision.

[5]  Berthold K. P. Horn,et al.  Determining Optical Flow , 1981, Other Conferences.

[6]  José Antonio Torres Arriaza,et al.  Competitive neural-net-based system for the automatic detection of oceanic mesoscalar structures on AVHRR scenes , 2003, IEEE Trans. Geosci. Remote. Sens..

[7]  Ling-Hwei Chen,et al.  A high-speed algorithm for elliptical object detection , 1996, IEEE Trans. Image Process..

[8]  R. Delmas,et al.  Automatic segmentation of oceanic eddies on AVHRR thermal infrared sea surface images , 1995, 'Challenges of Our Changing Global Environment'. Conference Proceedings. OCEANS '95 MTS/IEEE.

[9]  Ronald J. Holyer,et al.  Circle detection for extracting eddy size and position from satellite imagery of the ocean , 1994, IEEE Trans. Geosci. Remote. Sens..

[10]  Bülent Sankur,et al.  Survey over image thresholding techniques and quantitative performance evaluation , 2004, J. Electronic Imaging.

[11]  Sarah H. Peckinpaugh,et al.  Edge detection applied to satellite imagery of the oceans , 1989 .

[12]  Karim Faez,et al.  Fast Circle Detection Using Gradient Pair Vectors , 2003, DICTA.

[13]  A. Campbell,et al.  Progress in Artificial Intelligence , 1995, Lecture Notes in Computer Science.

[14]  Nuno C. Marques,et al.  Automatic Detection of Meddies Through Texture Analysis of Sea Surface Temperature Maps , 2005, EPIA.