Geografic-Information-System/raster/r.bitpattern/r.bitpattern.html

<h2>DESCRIPTION</h2>

<em>r.bitpattern</em> performs bit pattern comparisons.
The module can be used to pixelwise verify a satellite image
for low quality pixels if a Quality Control Bit Index map is
provided (e.g. as for MODIS sensor maps).

The functionality is two-fold:

<ol>
<li>define position: set bit(s) to 1 which shall match,
   then convert this position pattern to integer, set pattern=
   parameter with that integer value
<li>define pattern *value* which should be in that position:
   first bit pattern of value, convert to integer, set
   patval= parameter
</ol>

If several bitpatterns have to be tested, the resulting maps
can be used to exclude low quality pixel in the input satellite
image using <em>r.mapcalc</em> (OR and NOT operators).

<h2>EXAMPLE</h2>

<ol>
<li>define position:
<pre>
	xx xx 1x xx
	binary: 1000 -> integer: 8 -> pattern=8
</pre>

<li>define value:
<pre>
        Ex.: we want to check for 0 in that position
	xx xx 0x xx
	binary: 0000 -> integer: 0 -> patval=0
        if value can be arbitray (0/1), then assume 0 value
</pre>
</ol>

<h2>SEE ALSO</h2>

<em>
<a href="i.modis.qc.html">i.modis.qc</a>,
<a href="r.mapcalc.html">r.mapcalc</a>
</em>

<h2>AUTHORS</h2>

Radim Blazek, Markus Neteler

<p><i>Last changed: $Date$</i>