Hi Avinash,

Supervised classification would be appropriate to use when you have some knowledge about your study site since you need to designate training areas for the classifier to work. You can get information about crop types from farmers, air photos, regional agriculture offices, etc. Good luck! Best wishes, Kemal

Dear sir,

I have GPS point of different-different crops . Can I use these points for making signatures.

Yes, you can. However, be careful when you do accuracy assessment. You don't want to use the training points for validation. This will result in bias and inflated validation statistics. I would recommend that you save some of your field data for validation if that were your goal for collecting field data. Good luck. 

Thank you so much Dr. Gokkaya for your valuable respopnse.