While executing tasks such as sea surveilling

maritime searching and rescue

sea pollution monitoring utilizing remote sensed images

the coastal line feature should be determined at first. Thresholding method is a type of simple but valid method for image segmentation

likewise

they can be used to detect coastal line feature in remote sensed images. However

while conventional thresholding methods used to do it

they are always short of enough discriminating ability to objects' shadow

weak scattering vegetations

dark artificial buildings

sea gulf blurred by noise along costal line. This paper proposes a multi threshold based morphological approach

which divides the isolated regions by thresholding detecting into intra continent

exterior sea

and along coastal isolated regions at first

and then utilizes two definitions and morphological operators to process along coastal regions further so as to improve the detecting accuracy and decreasing false detecting

especially to enhance detecting accuracy for above objects' shadow

vegetations and dark artificial builds. Experiments are executed and the results exhibit the proposed approach possessing better performance than conventional thresholding approach.