i.ortho.photo(1)	      Grass User's Manual	      i.ortho.photo(1)



NNAAMMEE
       ii..oorrtthhoo..pphhoottoo  - An interactive imagery function for the ortho-rectifi-
       cation of imagery group files.
       _(_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..oorrtthhoo..pphhoottoo

DDEESSCCRRIIPPTTIIOONN
       _i_._o_r_t_h_o_._p_h_o_t_o allows the user to ortho-rectify imagery group files.  An
       imagery	group  consists  of several scanned aerial photographs (raster
       files) of a common area.  Imagery groups can  be  created  or  modified
       using  the  GRASS  Image Processing Program _i_._g_r_o_u_p, or using the first
       menu option described below.  _i_._o_r_t_h_o_._p_h_o_t_o guides the user through the
       steps  required	to  ortho-rectify the raster files in a single imagery
       group.


       The first menu in _i_._o_r_t_h_o_._p_h_o_t_o provides the user  with	the  following
       options:

       Initialization Options:
	      1) Select/Modify imagery group

	      2) Select/Modify imagery group target

	      3) Select/Modify target elevation model

	      4) Select/Modify imagery group camera


       Transformation Parameter Computation:
	      5) Compute image-to-photo transformation parameters

	      6) Initialize exposure station parameters

	      7) Compute photo-to-target transformation parameters


       Ortho-rectification Option:
	      8) Ortho-rectify imagery group raster files

       RETURN to exit
	      >

       To  ortho-rectify aerial images the user has to follow the menu options
       step by step. Generally the user builds a target location containing  a
       projected  DEM  and  a map reference (topo sheet or other map). Another
       xy-location will contain the aerial  photo.  The  entire  rectification
       process is started within the xy-location. First the target to the pro-
       jected location has to be set (i.target),  then	the  image  references
       (fiducial  points) will be defined. After describing the camera parame-
       ters, reference points from aerial image to the	topo  sheet  from  the
       target location will be set. The local elevation will be taken from the
       target DEM. Finally the aerial image will be rectified.


       The options to follow are described as follows:

       _1_. _S_e_l_e_c_t_/_M_o_d_i_f_y _i_m_a_g_e_r_y _g_r_o_u_p
	      The current imagery group is display at the top of the  previous
	      menu.   You  may	select another (new or existing) imagery group
	      for the ortho-rectification program  using  option  (1).	 After
	      choosing	option	(1) you will be prompted for the name of a new
	      or existing imagery group.  Option (1)  using  the  GRASS  Image
	      Processing  Program  _i_._g_r_o_u_p,  for  creation  or modification of
	      imagery groups.  For more information on imagery group  creation
	      or modification please the the GRASS manual page for _i_._g_r_o_u_p.

       _2_. _S_e_l_e_c_t_/_M_o_d_i_f_y _i_m_a_g_e_r_y _g_r_o_u_p _t_a_r_g_e_t
	      The target location and mapset may be selected or modified using
	      option (2).  After choosing option (2) you will be prompted  for
	      the  names  of  the target location and mapset, where the ortho-
	      rectified raster files will reside.  The target location is also
	      the  location  from which the elevation model (raster file) will
	      be selected -- see option (3).  Option (2) uses the GRASS  Image
	      Processing  Program  _i_._t_a_r_g_e_t,  for selection or modification of
	      the imagery group target location and mapset.  For more informa-
	      tion  on	imagery group selection or modification please the the
	      GRASS manual page for _i_._t_a_r_g_e_t.

       _3_. _S_e_l_e_c_t_/_M_o_d_i_f_y _t_a_r_g_e_t _e_l_e_v_a_t_i_o_n _m_o_d_e_l
	      Option (3) allows you to select the raster file from the	target
	      location to be used as the elevation model.  The elevation model
	      is required for both the computation of photo-to-target  parame-
	      ters  (option  6) and for the ortho-rectification of the imagery
	      group files (option 8).  The raster file select for  the	eleva-
	      tion model should cover the entire area of the image group to be
	      ortho-rectified.	Currently, the elevation model raster file  is
	      expected to be in units of meters.  DTED and DEM files are suit-
	      able for use as the elevation model in  the  ortho-rectification
	      program.	 After	selection  option (3) you will be prompted for
	      the name of the raster file in the target location that you want
	      to use as the elevation model.

       _4_. _S_e_l_e_c_t_/_M_o_d_i_f_y _i_m_a_g_e_r_y _g_r_o_u_p _c_a_m_e_r_a
	      Using  option  (4)  you may select or create an camera reference
	      file that will be used with the current imagery group.  A camera
	      reference file contains information on the internal characteris-
	      tics of the aerial camera, as well as the geometry of the  fidu-
	      cial  or reseau marks.  The most important characteristic of the
	      camera is its focal length.  Fiducial or reseau marks  locations
	      are  required  to  compute the scanned image to photo-coordinate
	      transformation  parameter  (option  5).	For  a	more  detailed
	      description  of  option (4) please see the GRASS manual page for
	      _p_h_o_t_o_._c_a_m_e_r_a.

       _5_. _C_o_m_p_u_t_e _i_m_a_g_e_-_t_o_-_p_h_o_t_o _t_r_a_n_s_f_o_r_m_a_t_i_o_n _p_a_r_a_m_e_t_e_r_s
	      The scanned image to photo-coordinate transformation  parameters
	      are  computed  using option (5).	In this interactive option you
	      associate scanned reference  points  (fiducials,	reseau	marks,
	      etc.)  with their known photo coordinates from the camera refer-
	      ence file.  Complete documentation for this option is  available
	      under the manual entry _p_h_o_t_o_._2_i_m_a_g_e.

       _6_. _I_n_i_t_i_a_l_i_z_e _e_x_p_o_s_u_r_e _s_t_a_t_i_o_n _p_a_r_a_m_e_t_e_r_s
	      The  use of photo.init (menu 6) is only required when rectifying
	      a tilted or oblique aerial photo.

	      If option (6)  is  selected,  initial  camera  exposure  station
	      parameters  and  initial	variances may be selected or modified.
	      Complete documentation for this option is  available  under  the
	      manual entry _p_h_o_t_o_._i_n_i_t.

       _7_. _C_o_m_p_u_t_e _p_h_o_t_o_-_t_o_-_t_a_r_g_e_t _t_r_a_n_s_f_o_r_m_a_t_i_o_n _p_a_r_a_m_e_t_e_r_s
	      The  photo to target transformation parameters are compute using
	      option(7).  Here control	points	are  marked  on  one  or  more
	      imagery  group  files and associated with there known positional
	      and elevation  coordinates.   Complete  documentation  for  this
	      option is available under the manual entry _p_h_o_t_o_._2_t_a_r_g_e_t.

       _8_. _O_r_t_h_o_-_p_h_o_t_o _i_m_a_g_e_r_y _g_r_o_u_p _f_i_l_e_s
	      Option  (8) is used to perform the actual image ortho-rectifica-
	      tion after all of the transformation parameters have  been  com-
	      puted.  Ortho-rectified raster files will be created in the tar-
	      get location for each selected  imagery  group  file.   You  may
	      select  either  the current window in the target location or the
	      minimal bounding window for the ortho-rectified image.  Complete
	      documentation  for  this	option	is  available under the manual
	      entry _p_h_o_t_o_._r_e_c_t_i_f_y.


NNOOTTEESS
       _i_._o_r_t_h_o_._p_h_o_t_o currently requires the elevation model to be  in  meters,
       and the target location to be a metric coordinate system.

SSEEEE AALLSSOO
       _p_h_o_t_o_._c_a_m_e_r_a

       _p_h_o_t_o_._2_i_m_a_g_e

       _p_h_o_t_o_._2_t_a_r_g_e_t

       _p_h_o_t_o_._i_n_i_t

       _p_h_o_t_o_._r_e_c_t_i_f_y

AAUUTTHHOORR
       Mike Baba,  DBA Systems, Inc.


       Updated rectification and elevation map to FP 1/2002 Markus Neteler

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_3_/_0_9_/_0_9 _1_3_:_1_0_:_1_8 _$



GRASS 5.0						      i.ortho.photo(1)
