Parent Topic: <A href="http://www.pcigeomatics.com/cgi-bin/pcihlp/GCPWORKS|Hints+and+Tips">Hints and Tips</a><hr>
<H4>Correcting PseudoColoured Images</H4>
GCPWorks is capable of correcting pseudo-coloured images, or using 
psuedo-coloured images as reference images for GCP collection; however,
some special consideration apply.
<P>
<UL>
<LI> No opportunity is provided to load PCT (Pseudo-Colour Tables).  The 
PCT must already be the default PCT for the selected image channel.
If this is not the case, the File Utility (File-&gt;Utility...) can be
used to edit the metadata for the pseudo coloured channel.  It should 
have a metadata entry something like ``DEFAULT_PCT_REF: gdb:{PCT:2}''
assuming that segment 2 is the desired PCT segment. 
</UL>
<UL>
<LI> Pseudo-colour only works in GCPWorks with single channels.  For example
three channels from the ``Uncorrected Image'' and one PCT channel
from the ``Georeferenced Database'' would NOT work.  The three channels
would show as RGB and the one channel would be reused three times
and would appear as one BW channel and the associated PCT would not
be used.
</UL>
<PRE>
   However using one of the three RGB channels as one BW channel and
   one channel as pseudo-colour would work.

   This limitation only effects the display of the images in collecting
   GCPs.  It does not effect access to the number of channels to
   process in the ``Perform Registration to Disk'' step.
</PRE>
<UL>
<LI> The ``Video Mode Control'' next to the PCI logo along the bottom edge
of the image windows can be used to switch between PCT, and Black and
White mode.  Note that RGB, B&amp;W1, B&amp;W2, and B&amp;W3 modes will be treated
as the same thing. 
</UL>
<UL>
<LI> Colour Matching is essentially useless for pseudo-coloured images, and 
should be avoided if either the uncorrected, or the georeferenced image
is pseudo-coloured. 
</UL>
<UL>
<LI> If a new file is created to register into in the final registration 
to disk panel, and a PCT is referenced on the source image, it will be
copied to the newly created file.  In other situations it may be necessary
to use the File Utility, or ImageWorks to transfer the PCT from the 
uncorrected file to the corrected file. 
</UL>
<UL>
<LI> Preregistration checking is largely useless unless the source and 
destination images share the same PCT. 
</UL>
<UL>
<LI> Only nearest neighbour resampling should be used when registering 
pseudo-coloured images.  Other resampling methods implicitly assume
greyscale images. 
</UL>
<hr>
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