area of water body in a grey color image

how to get area of water body in one band of a landsat image

[KSSV]

What data you have? What exactly you want to do?

[Poornima Posa]

i have band 4 of a landsat data, i need to find area of waterbody in that band

Answer 1

[Bjorn Gustavsson]

If the water-surface are flatter than the not-water-surfaces (seems reasonable assumption for standard optical satellite imaging without additional information), then you might try to look after regions where the magnitude of the gradients are small:

Im = double(your_one_band_landsat_image);
[dIdx,dIdy] = gradient(Im);
d2I = del2(Im);
subplot(1,3,2)
imagesc(Im)
subplot(1,3,1)
imagesc(d2I)
subplot(1,3,3)
imagesc(abs(dIdx)+abs(dIdy)) % other measures of flatness are also available

HTH

Answer 2

[yanqi liu]

sir，may be upload some image sample to develop.