photo.camera(1) 	      Grass User's Manual	       photo.camera(1)



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NNAAMMEE
       _p_h_o_t_o_._c_a_m_e_r_a  - An imagery function that creates or modifies entries in
       a camera reference file.
       _(_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
       _p_h_o_t_o_._c_a_m_e_r_a option must be selected from the  GRASS  Image  Processing
       Program _i_._o_r_t_h_o_._p_h_o_t_o .

DDEESSCCRRIIPPTTIIOONN
       _p_h_o_t_o_._c_a_m_e_r_a  creates  or  modifies entries in a camera reference file.
       For ortho-photo rectification, a camera reference file is required  for
       computation of scanned image to photo-coordinate transformation parame-
       ters.  There are two coordinate systems: The  image  coordinate	system
       (in  pixels)  and  the  photo  coordinate system (in milli-meters). The
       inner orientation establishes a relation between  the  pixels  and  the
       image coordinates with help of fiducial marks.


       The first prompt in the program will ask you for the name of the camera
       reference file to be created or modified.  You may create a new	camera
       reference  file	by  entering  a new name, or modify an existing camera
       reference file by entering the name of an existing camera file.


       After entering the camera file name, following menu is displayed:


       Please provide the following information




	    CAMERA NAME:	       _c_a_m_e_r_a _n_a_m_e______
	    CAMERA IDENTIFICATION:     _i_d_e_n_t_i_f_i_c_a_t_i_o_n___
	    CALIBRATED FOCAL LENGTH mm.:_________________
	    POINT OF SYMMETRY (X)   mm.:_________________
	    POINT OF SYMMETRY (Y)   mm.:_________________
	    MAXIMUM NUMBER OF FIDUCIALS:_________________

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

       The camera name and identification describe the camera reference  file.
       The  calibrated focal length and the point of symmetry are used in com-
       puting the photo-to-target  transformation  parameters.	 These	values
       should be entered from the camera calibration report (usually available
       from the photograph supplier).


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       _1_9_8_5


       The photo coordinate system origin is the so-called calibrated  princi-
       pal  point  (PP, Principal Point of Symmetry) which is in the center of
       the image.  The origin of the axes is at the intersection of the  radii
       traced  from  the fiducial marks. In the ideal case of no deviations in
       the camera (see camera calibration certificate) the center is the  ori-
       gin  and  the  values  are 0 for both X and Y of Point of Symmetry. But
       usually the principal point does not fall on the  intersection  of  the
       radii at the center of the picture. This excentricity is usually of the
       order of a few micrometers.


       You are then asked to enter the X and Y photo coordinates of each fidu-
       cial  as  follows.   These  fiducials (or reseau) marks are index marks
       imaged on film which serve as reference photo  coordinate  system.  The
       maximum	number	of  fiducials will determine the number of fiducial or
       reseau coordinate pairs to be entered below. The origin is  the	center
       of  the image (or the point of symmetry) and X and Y are left-right and
       up-down. The order is up to the	user,  but  must  be  kept  consistent
       throughout the rectification process.


       On  this  screen  you should enter the fiducial or reseau photo-coordi-
       nates as given in the camera calibration report. The X, and  Y  coordi-
       nates are in milli-meters from the principle point.


       Please provide the following information

	    Fid# FID ID 	  X	     Y

	    1__  _____		0.0___	  0.0___
	    2__  _____		0.0___	  0.0___
	    3__  _____		0.0___	  0.0___
	    4__  _____		0.0___	  0.0___
	    5__  _____		0.0___	  0.0___
	    6__  _____		0.0___	  0.0___
	    7__  _____		0.0___	  0.0___
	    8__  _____		0.0___	  0.0___
	    9__  _____		0.0___	  0.0___
	    10_  _____		0.0___	  0.0___

		      next:  end__

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

       The  input display is repeated until the number of MAXIMUM FIDUCIALS is
       reached.



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       _p_h_o_t_o_._i_n_i_t




AAUUTTHHOORR
       Mike Baba, DBA Systems, Inc.



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GRASS 5.0						       photo.camera(1)
