Crosta Transformation for Landsat TM images (ENVI Classic)

This program performs Crosta transformations (Principal Components with just a well-know subset of TM bands). 

The Crosta H and F reference is as follows: 

Loughlin W.P. 1991, Principal Component Analysis for Alteration Mapping. Proceedings 8th Thematic Conference on Geologic Rmote Sensing, Denver, Co. USA, V1, pp293-306, April 29th - may 2nd. 1991. 

The paper will outline how to run a Crosta analysis for hydroxyl (H) and for iron oxides (F). For the latter however, it uses a PCA on Landsat TM bands 1,3,4 and 5. This is now broadly accepted as being red iron oxide (Fr) and a second PCA using bands 2,3,4 and 5 gives the yellow iron oxides (Fy).

To run the Crosta program:

1.- Place the crosta.pro (or crosta.sav) file in the /Exelis/enviXX/save_add directory.
2.- Two ways to run it:
  - By typing COSTRA in the IDL command line.
- Entering a new item in the ENVI menu. Edit the /enviXX/menu/envi.men file
 and enter something like this:
 2 {Crosta Transformations} {crosta} {crosta}
(the '2' depends on the level of menu where we are including this new entry).