i.pca(1)		      Grass User's Manual		      i.pca(1)



NNAAMMEE
       ii..ppccaa  - Principal components analysis (pca) program for image process-
       ing.
       _(_G_R_A_S_S _I_m_a_g_e _P_r_o_c_e_s_s_i_n_g _P_r_o_g_r_a_m_)

SSYYNNOOPPSSIISS
       ii..ppccaa
       ii..ppccaa hheellpp
       ii..ppccaa iinnppuutt==_n_a_m_e_,_n_a_m_e[_,_n_a_m_e_,_n_a_m_e,...]  oouuttppuutt==_n_a_m_e rreessccaallee==_m_i_n_,_m_a_x

DDEESSCCRRIIPPTTIIOONN
       _i_._p_c_a is an image processing program based on the algorithm provided by
       Vali (1990), that processes n (2 >= n) input raster map layers and pro-
       duces n output raster map layers containing the principal components of
       the  input data in decreasing order of variance ("contrast").  The out-
       put raster map layers are assigned names with .1, .2, ... .n  suffixes.
       The   current  geographic  region  definition  and  mask  settings  are
       respected when reading the input raster map layers.  When  the  rescale
       option is used, the output files are rescaled to fit the min,max range.

OOPPTTIIOONNSS
   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e_,_n_a_m_e[_,_n_a_m_e_,_n_a_m_e,...]
	      Name of two or more input raster map layers.

       oouuttppuutt==_n_a_m_e
	      The output raster map layer name to which  suffixes  are	added.
	      Each  output  raster  map  layer is assigned this user-specified
	      _n_a_m_e with a numerical (.1, .2, ...

       rreessccaallee==_m_i_n_,_m_a_x
	      The  optional  output  category  range.  (Default:   0,255)   If
	      rescale=0,0,  no rescaling is performed on output files.


NNOOTTEESS
       Richards  (1986)  gives	a good example of the application of principal
       components analysis (pca) to a time  series  of	LANDSAT  images  of  a
       burned region in Australia.

SSEEEE AALLSSOO
       Richards, John A., RReemmoottee SSeennssiinngg DDiiggiittaall IImmaaggee AAnnaallyyssiiss, Springer-Ver-
       lag, 1986.


       Vali, Ali R., Personal communication, Space Research Center, University
       of Texas, Austin, 1990.


       _i_._c_c_a

       _i_._c_l_a_s_s

       _i_._f_f_t

       _i_._i_f_f_t

       _m_._e_i_g_e_n_s_y_s_t_e_m

       _r_._c_o_v_a_r

       _r_._m_a_p_c_a_l_c

AAUUTTHHOORR
       David Satnik, GIS Laboratory,


       Major modifications for GRASS 4.1 were made by

       Olga Waupotitsch and Michael Shapiro, U.S.Army Construction Engineering
       Research Laboratory

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_3 _$



GRASS 5.0							      i.pca(1)
