if an satellite image contain different features like forest area,reservoir ,hill then how to count areas of forest, hill ,reservoir separately?

if an satellite image contain different features like forest area,reservoir ,hill then how to count areas of forest, hill ,reservoir separately?

Answer 1

[Image Analyst]

You need to do "classification". It's a whole field of image analysis, especially important in remote sensing. Look up papers and algorithms here: http://iris.usc.edu/Vision-Notes/bibliography/contentscartog.html#Cartography,%20Aerial%20Images,%20Remote%20Sensing,%20Buildings,%20Roads,%20Terrain,%20ATR. It's far too complicated to just give you a 500 line snippet of code here. You're going to have to do development of an algorithm that works with your images.

[Image Analyst]

How do you want to draw a boundary? With plot() from the boundary coordinates of the binary image of the forest? If so, do this

boundaries = bwboundaries(binaryImage);
imshow(originalImage);
title('Outlines, from bwboundaries()');
hold on;
boundaries = bwboundaries(binaryImage);
numberOfBoundaries = size(boundaries, 1);
for k = 1 : numberOfBoundaries
  thisBoundary = boundaries{k};
  plot(thisBoundary(:,2), thisBoundary(:,1), 'g', 'LineWidth', 2);
end
hold off;

do this for any class you want the boundaries of. Do one at a time, getting a new binary image for each class. Plot boundaries in a different color for each class if you want.

[ajay]

nice

Answer 2

[ajay]

I classified the image as forest,reservoir etc but i want to draw a boundary and calculate the boundary area?

[Image Analyst]

You can use your classified image to create a binary image.

binaryImage = classifiedImage == classNumberThatYouWant;

Then use bwboundaries

boundaries = bwboundaries(binaryImage);