Dear all,

I am trying to do some unsupervised classification on hyperspectral images using the ISODATA tool. However, I find some unclarity between the GUI options and the ENVI help.

ISODATA requires to specify thresholds about standard deviation of the data ("Maximum class Stdv") and the help states that this standard deviation should be expressed in "DN" (which I guess means "Digital Number"). But what does it means exactly? I am working on scaled reflectance images, how should I convert them to DN?

Also the default standard deviation threshold is 1, which seems odd even if working with DNs. Does this mean that ISODATA performs some kind of normalization on the data?

Thanks for the clarification!