High grey value from the Sobel filtering indicated the presence
of an edge between two objects. The root mean square (RMS) of two
3 3 templates produced a mean brightness value 118.17 which
was higher than 105 and 72.19 produced by the average and median
filters respectively. High values in the analysis of the processed
histogram were indicative of edge lines detection in the image, that
were later visualized as the boundary lines between sea and land.
Using an edge filter helped compute the mean of the absolute
difference between the grey value at the central pixel and at each of
its neighbors within the filter window. The mean value of the
filtration was 92.12 equaling to the value of the original image
which is processed by the average and median filters. The median
and standard deviation values were 79 and 60.26 respectively.