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<h2>NAME</h2>
<em><b>photo.2image</b></em>
<H2>DESCRIPTION</H2>
<EM>photo.2image</EM> is an imagery function that enables
you to mark fiducial or reseau points on an image to be
ortho-rectified and then computes the image-to-photo
coordinate transformation parameters. The coordinates of
the fiducials or reseau marks can be choosen for a camera
reference file.
<P>
During the process of marking reference points with known
photo coordinates, you may compute the RMS (root mean
square) error for each reference point entered.
<EM>photo.2image</EM> does this by calculating the
transformation equation (the same one that is calculated by
<EM><A HREF="i.points.html">i.points</A> </EM>),
and then plugging these results into an equation for RMS
error.
<P>
<EM>photo.2image</EM> offers a zoom option to locate
precisely the fiducial or reseau point to be marked on an
image.
<P>
To run <EM>photo.2image</EM>, a graphics monitor is
required.
<P>
The procedure for marking fiducial or reseau points,
entering known photo-coordinates, and analyzing the RMS
error is described below.
<P>
The terminal screen displays this message:
<P>
<B>use mouse now...</B>
<P>
The graphics monitor displays the following screen:
<PRE>
+---------------------------+---------------------------------+
|imagery | |
+---------------------------+---------------------------------+
| | |
| | |
| | |
| | |
| | |
| | |
| | |
+---------------------------+---------------------------------+
| | |
| | |
| | |
| | |
| | |
| | |
| | |
+---------------------------+---------------------------------+
| | |
+---------------------------+---------------------------------+
</PRE>
<P>
A pop-down menu like that shown below will be superimposed on the
left half of the screen:
<P>
<PRE>
+------------------------------------------+
| Double click on raster map to be plotted |
| Double click here to cancel |
+------------------------------------------+
+----------------+
|Mapset imagery |
+-------+--------+
|gs13.1 | gs21.1 |
+-------+--------+
|gs14.1 | gs22.2 |
+-------+--------+
</PRE>
Any single file in the imagery group may be used on which to mark
points, and you may mark points on more than one file
in the imagery group to accumulate the suggested minimum number of
4-8 fiducial or ressue points.
The imagery file selected is displayed in the upper
left quadrant of the screen.
<P>
<H2>CAMERA FILE</H2>
The camera reference file may be viewed by placing the mouse
cross hairs on the words CAMERA. The camera reference file
will be displayed in the lower left quadrant of the display:
<P>
<PRE>
|---------------------------------------------------------------|
|Camera Reference File |
|---------------------------------------------------------------|
| CAMERA NAME : camera name |
| CAMERA ID : L1234 |
| CAMERA CFL : 153.021 mm. |
| CAMERA XP : 0.050 mm. |
| CAMERA XP : 0.056 mm. |
| number of fid. 4 |
|---------------------------------------------------------------|
| |
|ID (X PHOTO) mm. (Y PHOTO) mm. |
|_______________________________________________________________|
|1 -105.023 110.123 |
|2 107.987 109.834 |
|3 110.965 -104.329 |
|4 -103.932 -110.352 |
|_______________________________________________________________|
</PRE>
<P>
The following menu is displayed at the bottom
of the graphics display:
<P>
<B>
<PRE>
+-----+------+-----------+--------+---------+-------------------+-------------+
|Quit | Zoom | Plot Cell | Camera | Analyze | Input->KEYBOARD | CAMERA FILE |
+-----+------+-----------+--------+---------+-------------------+-------------+
</PRE>
</B>
<P>
<H2>ZOOM</H2>
To magnify the displayed file, you must
place the mouse cross hairs on the word ZOOM. The following menu
will then be displayed at the bottom of the screen:
<P>
<B>
<PRE>
+-------+-----+-------++--------------------+
|Cancel | Box | Point ||Select type of ZOOM |
+-------+-----+-------++--------------------+
</PRE>
</B>
<P>
You have the option of identifying the zoom window either by using
the mouse to make a box, or by using the mouse to mark the center
of the desired window, and adjusting the magnification factor.
The terminal screen will display a mouse button menu to guide you in
identifying the window. The section of the image within the zoom window
will be displayed in the upper right hand quadrant.
<P>
<H2>MARKING REFERENCE POINTS</H2>
To mark the known reference points (fiducial marks, reseau marks, etc.)
on the image, you must place the mouse cross hairs
on the corresponding location on the image to be marked and press
the left hand button on the mouse. A diamond shaped symbol will be marked
on the image.
<P>
If you wish to use the camera reference file only as a
comparative reference, then the keyboard can be chosen as
the means to input photo coordinates corresponding to the marked
reference points on the image. This is done by placing the mouse
cross hairs on the word KEYBOARD and pressing the left
button on the mouse.
<P>
The following menu is displayed on the graphics terminal:
<P>
<PRE>
+------------------------------------+--------------------------+
|Point 1 marked at IMAGE COORDINATES | |
|east: 1023.77 | |
|north: 506.56 | |
| | |
| | |
| | |
| | |
| | |
+------------------------------------+--------------------------+
|Enter PHOTO COORDINATES as x and y: |
+---------------------------------------------------------------+
</PRE>
</B>
<P>
You then enter the known (x,y) photo coordinates, relative
to the perspective center, for the reference
point marked on the image. If you
do not wish to enter a coordinate, simply hit RETURN to continue;
the marked reference point will disappear.
<P>
If you select the CAMERA FILE option, then reference points
marked on the image will be associated with selected photo
coordinates from the displayed camera reference file. In this option,
when you mark a point on the image, the following menu is
displayed on the graphics terminal:
<P>
<PRE>
-------------------------------------------------------------
CANCEL Double click on the fiducial mark to be referenced
-------------------------------------------------------------
</PRE>
<P>
If you would like to select the photo coordinates of a displayed
reference mark, this can be accomplished by placing the mouse
cross hairs on the reference point to be selected and pressing
the left button on the mouse twice. After a reference point is selected
from the display, you are prompted with "Look ok? (Y/N)".
If you respond with no, the reference point is ignored.
If you respond with yes, the following is displayed on the terminal:
<P>
<P>
<PRE>
+----------------------------------------+--------------------------+
|Point 1 marked at IMAGE COORDINATES | |
|east: 1023.77 | |
|north: 1065.41 | |
| | |
| | |
|Point 1 referenced at PHOTO COORDINATES | |
|X: -105.023 | |
|Y: 110.122 | |
| | |
| | |
| | |
| | |
| | |
+----------------------------------------+--------------------------+
| use mouse now... |
+----------------------------------------+--------------------------+
</PRE>
</B>
<P>
The photo coordinates and the corresponding image coordinates are
automatically saved in the photo_points file associated with the imagery
group.
<P>
<P>
<H2>ANALYZE</H2>
After a number of points have been marked (4 to 8), you can
check the RMS error of the points marked on the image. This is done
by placing the mouse cross hairs on the word ANALYZE at the bottom
of the monitor. An error report resembling the one shown below
is superimposed on the monitor:
<P>
<PRE>
+--------------------------------------------------------------------+
| error image photo |
| |
|# row col photo east north x y |
|1 0.0 -0.9 1.0 1048.5 -144.8 -105.023 110.122 |
|2 0.4 1.0 1.3 2153.1 -567.2 107.987 109.834 |
|3 -1.2 -0.5 0.6 1452.8 -476.5 110.965 -104.329 |
|4 1.1 0.5 1.3 1034.0 -109.2 -103.932 -110.352 |
| |
+--------------------------------------------------------------------+
| overall rms error: 4.46 |
+--------------------------------------------------------------------+
</PRE>
<P>
The following menu then appears at the bottom of the monitor:
<P>
<PRE>
+-----+-------+------+-----------------------------------------------+
|DONE | PRINT | FILE | Double click on point to be included/excluded |
+-----+-------+------+-----------------------------------------------+
</PRE>
</B>
<P>
The RMS error for the image is given under the column
TITLEd "error" and subTITLEd "row" and "col". In the above
report, point number 1 is 0.0 rows and -0.9 columns from
the predicted location calculated from the transformation
equation. The RMS error for the photo coordinates is
listed under the heading "photo". This is the RMS error
for the x and y coordinates of the photo coordinates but it
is presented in the table using one general value. The
overall RMS error is displayed at the bottom of the screen
in milimeters. Points that create high RMS error are
displayed in red on the monitor (represented here in
italics).
<P>
The location of the point marked on the imagery group file
is given under the heading "image" and the subheadings
"east" and "north". The location of the point in the photo
coordinates is given under the heading "photo" and the
subheadings "x" and "y". If you would like to exclude or
include a point, this can be accomplished by placing the
mouse cross hairs on the point number to be included (if
the point is absent) or excluded (if the point is
displayed) and pressing the left button on the mouse
twice. When a point is excluded, it is not afterwards
included in the calculation of the RMS error, or included
in the final transformation matrix. However, it can be
retrieved within <EM>photo.2image</EM> at any time by
double clicking with the mouse as described above.
<P>
<H2>QUIT</H2>
To end the <EM>photo.2image</EM> program place the mouse cross hairs
on the word QUIT; the marked reference points (including coordinates)
will be saved.
<P>
<H2>NOTES</H2>
A good rule of thumb is to mark at least 4 to 8 points which are
evenly distributed over the perimeter of the imagery
group file in order to obtain
an accurate transformation equation for the rectification process.
The RMS error may increase with more points added, but the
transformation equation will be more accurate.
<P>
An RMS error of less than or equal to approximately one resolution
unit (pixel) for the image being rectified is generally considered
acceptable.
<H2>SEE ALSO</H2>
<EM><A HREF="i.ortho.photo.html">i.ortho.photo</A></EM>,
<EM><A HREF="photo.camera.html">photo.camera</A></EM>,
<EM><A HREF="photo.2target.html">photo.2target</A></EM>,
<EM><A HREF="photo.init.html">photo.init</A></EM>,
<EM><A HREF="photo.rectify.html">photo.rectify</A></EM>
<H2>AUTHOR</H2>
Mike Baba, DBA Systems, Inc.
<p><i>Last changed: $Date: 2006-12-15 11:10:21 +0100 (Fri, 15 Dec 2006) $</i>
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