I want to do supervised classification in ArcGIS 9.3. I have a 321RGB composite of a pretty good quality which I want to use for supervised classification.
How can I create signature file which contains training sites, and how do I create training sites?
I do know what qualities are needed regarding the areas and the number of areas (number, all possible categories, spectrally separable etc.)
Best Answer
I have tried supervised classification in ArcGIS.
Firstly I would say that it is not the best software for classification.
As I did it, you can create training sites as points. Just create a shapefile (or geodatabase), add Integer field, click points over your image and assign classes as numbers. (I think you can also use polygon shapefile).
For signatures, go to ArcToolbox > Spatial Analyst Tools > Multivariate > Create Signatures. There just put your bands and training points.
ArcGIS doesn't show you the resulting signature file, however it is ASCII file and you can look inside, for example using Notepad++. For each band you can see something like this:
If you wish, you can plot the Means manually to see if they are separated, for example in Excel.
You can do a dendrogram for your classes Spatial Analyst Tools > Multivariate > Dendrogram.
Then you do actually classification Multivariate > Maximum Likelihood Classification. There you have only two tunable options: to say, how much uncertain pixels will remain unclassified (rejected), and probability weighting for classes; and request a confidence raster.
And the result looks like this:
For theorical information check classification help and signature help.
Actually, after several attempts I switched to Remote Sensing software.