i.rectify3(1)	       Grass User's Manual	    i.rectify3(1)



NNAAMMEE
       ii..rreeccttiiffyy33  -  An imagery function that rectifies an image
       by computing a coordinate  transformation  for  each  cell
       (pixel)	in  the image using the transformation parameters
       generated by the GRASS program _i_._p_o_i_n_t_s_3.

       _(_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..rreeccttiiffyy33

DDEESSCCRRIIPPTTIIOONN
       _i_._r_e_c_t_i_f_y_3 rectifies an image by using the  transformation
       paramters  generated  by  _i_._p_o_i_n_t_s_3.  Rectification is the
       process by which the geometry of an image is  made  plani-
       metric.	This is accomplished by mapping (transforming) an
       image from one coordinate system to  another.   In  _i_._r_e_c_-
       _t_i_f_y_3,  the coefficients computed by _i_._p_o_i_n_t_s_3 are used in
       an equation to convert x,y  coordinates	to  standard  map
       coordinates  for  each  cell  in  the image.  The user can
       select either a	POLYNOMIAL,  ORTHO-PHOTO,  or  LANDSAT-TM
       transformation  using _i_._p_o_i_n_t_s_3.  The result of _i_._r_e_c_t_i_f_y_3
       is an image with a standard map coordinate  system.   Upon
       completion of the program the rectified image is deposited
       in a previously targeted GRASS LOCATION_NAME and MAPSET.


       The GRASS programs _i_._t_a_r_g_e_t  and  _i_._p_o_i_n_t_s_3  must  be  run
       prior to _i_._r_e_c_t_i_f_y_3.


       The first prompt in the program asks the user for the name
       of the group containing the raster map layers to be recti-
       fied.

	      Enter imagery group to be rectified
	      Enter 'list' for a list of existing imagery groups
	      Enter 'list -f' for a verbose listing
	      Hit RETURN to cancel request
	      >

       The  user  is then asked to select the map layer(s) within
       the group to be rectified:

	      Please select the file(s) to rectify by  naming  an
       output file

		  spot.1 in demo:.........
		  spot.2 in demo:.........
		  spot.3 in demo:.........
		  spotclass in demo:spotrectify..
		  spotreject in demo:.........

	      (Enter  list  by any name to get a list of existing
       raster files)

		 AFTER COMPLETING ALL ANSWERS, HIT <ESC> TO  CON-
       TINUE
			       (OR <Ctrl-C> TO CANCEL)

       More than one raster map layer may be rectified at a time.
       Each raster map layer should have  a  unique  output  file
       name.


       Next  the  user	is  asked to select one of two geographic
       region settings:

	      Please  select  one  of  the following  options
		  1.:Use the current region in the  target  loca-
       tion
		  2.:Determine	the  smallest region which covers
       the image

       _i_._r_e_c_t_i_f_y_3 will only rectify that  portion  of  the  image
       that  occurs  within the chosen geographic region setting.
       Only that portion will be relocated  in	the  target  data
       base.  It is therefore important to check the current geo-
       graphic region settings in the target location  if  choice
       number one is selected.

NNOOTTEESS
       The rectification process may take an hour or more depend-
       ing on the resolution of the image, the number  of  files,
       and the size of the geographic region definition.


       The rectified (raster) image will be located in the target
       LOCATION when the  program  is  completed.   The  original
       unrectified raster map layers are not modified or removed.

SSEEEE AALLSSOO
       GRASS Tutorial: Image Processing



       _m_._p_r_o_j_, _s_._p_r_o_j_, _s_._p_r_o_j_, _v_._p_r_o_j_, _i_._g_r_o_u_p_, _i_._p_o_i_n_t_s_3_, _i_._r_e_c_-
       _t_i_f_y_, _i_._t_a_r_g_e_t


AAUUTTHHOORR
       Mike Baba, DBA Systems.


       Michael	Shapiro,  U.  S.  Army	Construction  Engineering
       Research Laboratory wrote the original _i_._r_e_c_t_i_f_y  program,
       from which the new program was developed.

       _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.rectify3(1)
