This is not a command in itself, but an option to the command i.ortho.photo

## NAME

photo.camera - An imagery function that creates or modifies entries in a camera reference file.
(GRASS Image Processing Program)

## SYNOPSIS

photo.camera option must be selected from the GRASS Image Processing Program i.ortho.photo .

## DESCRIPTION

photo.camera 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 parameters. 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:               camera name______
    	CAMERA IDENTIFICATION:     identification___
    	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 computing the photo-to-target transformation parameters. These values should be entered from the camera calibration report (usually available from the photograph supplier).

This example is the camera Zeiss LMK9 265-002A belonging to the Hellenic Military Geographical Survey (HMGS) and calibrated in December 1985

The photo coordinate system origin is the so-called calibrated principal 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 origin 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 fiducial 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-coordinates as given in the camera calibration report. The X, and Y coordinates 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.

## SEE ALSO

i.ortho.photo
photo.2image
photo.2target
photo.init

## AUTHOR

Mike Baba, DBA Systems, Inc.

Last changed: $Date: 2002/11/27 09:14:11 $