r.bitpattern 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:
define position: set bit(s) to 1 which shall match,
then convert this position pattern to integer, set pattern=
parameter with that integer value
define pattern *value* which should be in that position:
first bit pattern of value, convert to integer, set
patval= parameter
If several bitpatterns have to be tested, the resulting maps
can be used to exclude low quality pixel in the input satellite
image using r.mapcalc (OR and NOT operators).
EXAMPLE
define position:
xx xx 1x xx
binary: 1000 -> integer: 8 -> pattern=8
define value:
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