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



NNAAMMEE
       ii..ppccaa   -  Principal components analysis (pca) program for
       image processing.
       _(_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 algo-
       rithm provided by Vali (1990), that processes n (2  >=  n)
       input  raster  map layers and produces n output raster map
       layers containing the principal components  of  the  input
       data  in  decreasing  order of variance ("contrast").  The
       output 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-Verlag, 1986.


       Vali, Ali R., Personal communication, Space Research  Cen-
       ter, 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 Construc-
       tion 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)
