How to do a vegetation classification

[Daniela_06]

Hello everyone.

I am doing a classification for 2 different dates 2002 and 2012.

For the year 2002 I have a shapefile with polygons that show the classes (16) in total, using ERDAS and ENVI I was able to turn those polygons into training sites a do a proper classification. For the year 2012 I have no shapefile nor ground thruthing information and I am going to do a visual analysis of the 2002 classification map to create signatures for the 2012.

Now. I need to asses the deforestation of the area and my classification covers other classes that may be not necessary how ever I want to do use this classes for one classification and maybe do another classification of only vegetation.

I am using the color compsite 4,3,2, RGB false colour to appreciate vegetation. I would like to know how NDVI or vegetation indexes are used and how can use it to create the " only vegetation¨ classification I want to do.

Do NDVI is applied to the stacked images with the 3 layers or only to one band of the ETM satellite image? Once i have tge NDVI image how do I use it? does it substitues a layer in the RGB composite? Which one? what other indices can I use or band combinations to have a more acurrate vegetation classification?

Please help me, thank you for your time.