Which Tools do you use for Classification of Remote Sensing Data?

Which tool do you prefer to use for classification of remote sensing data, e.g. classifying land use, and why?

Which other tools have you tried, and why did you decide against them?

Answer

I use a number of tools depending on the type of classification I am trying to perform.

For general unsupervised/supervised classification I use ENVI, which has many options for classification methods (including some more advanced methods using neural networks and support vector machines). It is very easy to extend ENVI using the IDL programming language, and I have found that this often simplifies post-classification analysis (as you can write your own code to do this if needed).

If I want to perform object-based classification (which involves segmenting the image into objects and then classifying these objects, the benefits being that you can use aggregated properties of the objects such as means of the bands, shape and texture) I use eCognition, although I have also heard that ENVI EX is good if you don't need the power of eCognition.

If you're looking for free software then Opticks has a number of options for classification, although I've never got on very well with Opticks. Also, Spectral Python is a very nice tool that allow you to load images into NumPy arrays in Python and then process them. It includes a module containing various classification methods, and is very easy to extend.