Coastline detection
This experiment was based on a paper by Ireena A. Erteza on Automatic Coastline detection for use with SAR images.
It was found that the algorithm can be used more or less as is for multi spectral images, although it needs some tweaking to improve robustness.The following pictures show five stages in the detection process:
Original image.
Median filter applied two times.
Dilation filter applied to get rid of shadows and other dark spots on the land.
Edge detection is done by using a Sobel edge detector to get a gradient image.
Taking a threshold of 40 produced this image. The coastline is easily
recognizable and can be followed using a suitable contour following algorithm.