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 planimetric.  This is accomplished by map-
       ping (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 equa-
       tion 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	previ-
       ously 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 rectified.

	      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 CONTINUE
			       (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 location
		  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 geographic region settings in the target location if choice
       number one is selected.

NNOOTTEESS
       The rectification process may take an hour or  more  depending  on  the
       resolution  of the image, the number of files, and the size of the geo-
       graphic 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 Labora-
       tory 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)
