I want to obtain the size of unchanged, decreased, and increased area etc (just like shown in image below) from 2 classification images in 2000 and 2007.
How do I do this in ERDAS?
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You can do it by this way: 1. Go to 'Image Interpreter >>> Utilities >>> Change detection'. 2. Give before and after images. 3. It will produce the 'Difference' image as well as 'thematic image' of five classes namely decreased, some decreased, unchanged, some increase and increased.
From which you can calculate the size of your decreased, increased and unchanged.
If you are using ERDAS 2013, what you can do is go to raster, choose zonal change in the change detection panel, then choose image difference:
Make sure you specify correctly the before map and the after map images, then you can specify directories for both outputs for the change in image and the highlighted one as shown.
After specifying your threshold you can then run it by pressing OK. After getting your result, open the highlight change image result you got then right click on its layer to open the tables from there. You can now work with your classes as you are required. Hope this makes sense.