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There are two basic tiepoint operations - adding tiepoints and deleting
tiepoints.  When the Tiepoint Operation 
toggle is set to "Add", mouse clicks in the source and target windows 
(or in the source zoom and target zoom windows) will add tiepoints at 
the location of the click;  when the Tiepoint Operation toggle is set to 
"Delete", mouse clicks in the source and target windows 
(or in the source zoom and target zoom windows) will delete tiepoints, 
provided that a tiepoint is located \fIdirectly\fP under the mouse at the 
time of the click.  The procedure used to add and delete tiepoints is 
determined by the Tiepoint Mode, described below. 
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Tiepoint Mode
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	\fBSource And Destination\fP
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When the Tiepoint Mode (controlled by the value of the [-tp_mode] flag 
at the start of execution) is set to Source And Destination, the procedure 
to add 
tiepoint pairs is as follows.  First, click the mouse at the desired location
in either the source image or the source zoom window.  If the mouse is
clicked in the source image, a red tiepoint will appear in the source image;
if the region in which the new tiepoint is located is currently displayed in
the source zoom window, a red tiepoint will also appear in the zoom window.
If the mouse is clicked in the source zoom window, it will always appear in both
the source zoom window and the source image.  The tiepoint appears in red,
indicating that you must now match it with a tiepoint in the target window.
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Now, click the mouse at the desired location in either the target image
or the target zoom window.  If the mouse is clicked in the target 
image, a green tiepoint will appear in the target image; if the region 
in which the new tiepoint is located is currently displayed in the target 
zoom window, a green tiepoint will also appear in the zoom window.  If the 
mouse is clicked in the target zoom window, it will always appear in 
both the target zoom window and the target image.
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At the same time that the target tiepoint is created, its partner in the
source image will change its color from red to green, indicating that a 
tiepoint pair has been established.  You may now repeat the process to create
more tiepoint pairs.
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	\fBSource Only\fP
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When the Tiepoint Mode is set to Source Only, tiepoints are only created on
the source image;  in fact, there is no point in inputting a target image
at all, as it will not be used.  
This option is useful when tiepoint information is already available for
either the source or the target image, but the second tiepoint file
needs to be created interactively.  The resulting tiepoint file can
be used along with the original tiepoint file for warping the source image.  
vpolyco and vbilinco are two routines that will generate polynomial 
coefficients to map the source tiepoints onto the target tiepoints.  These 
coefficient files can then be used as the coefficients for vwarp to perform
image warping.
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The procedure to add individual tiepoints is
as follows. Click the mouse at the desired location in either the source 
image or the source zoom window.  If the mouse is clicked in the source image, 
a green tiepoint will appear in the source image; if the region in which the 
new tiepoint is located is currently displayed in the source zoom window, 
a green tiepoint will also appear in the zoom window.
If the mouse is clicked in the source zoom window, it will always appear in both
the source zoom window and the source image. 
This process may be repeated as many times as necessary.
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Zoom Type & Zoom Factor
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There are two methods for zooming on the source and target images-
Rubberband, and Point & Click.  Depending on what you are doing, one of the
methods may be more appropriate than the other. 
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	\fBPoint & Click\fP
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The Point & Click is the simpler, but less precise method of zooming.  
To change the location of the zoom area, click on the "Point & Click" 
action button, and follow that with a mouse click at the pixel in the 
image at which you want the center of the zoom area.  The contents of the 
zoom window will be immediately updated, so as to have the selected pixel 
of the image be at the center of the zoom window.
Under "Zoom Factor", go to either the "Source" or "Destination" selection, 
depending on whether you want to change the zoom factor of the source zoom 
window or the target zoom window.  Fill in the desired zoom factor, 
and hit <CR>. You will see the zoom window immediately update according 
to the new zoom factor.  
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	\fBRubberband\fP
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The Rubberbanding method of zooming is a little more complicated, but more 
precise.  To use the Rubberbanding method, click on the action button labeled, 
"Rubberband".  Then, go to the image, and click the mouse 
on the desired location of the upper left hand corner of
the zoom box to be created.  Holding the mouse button down, move the mouse
to the desired location of the lower right hand corner of the zoom box.  The
zoom box will be rubberbanded during this operation.  When the desired area
appears within the rubberbanded box, release the mouse button.  The zoom
area will be set within the rubberbanded box. The zoom factor is computed 
according to the bounds of the rubberbanded box, and the contents of the
zoom window are updated accordingly.  In addition, the contents of the zoom 
factor selection to the far right of the "Operations" pane will immediately 
be updated, informing you as to the exact zoom factor that was computed 
from the rubberbanding action.  Thus, when the Rubberbanding method of 
zooming is used, the "Zoom Factor" selection is an output, not an input.
The rubberbanded box will remain displayed in the image, to remind you of
the exact location of the zoom area.  
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