USER’S MANUAL__________________________________________________________________
228 _________________________________________________________________ M211322EN-D
6.4.2 Adjusting Threshold Qualifiers
The effect of the various threshold qualifiers for each output parameter are
discussed in this section. In optimizing thresholds for your application, it
is recommended that you change only one parameter (level or criterion) at
a time so that you can verify the effect. Some hints for optimizing the levels
for the default criteria are:
LOG To optimize the LOG level, display dBT or dBZ and select the
lowest value of the threshold that eliminates the display noise.
If the LOG level is set too high you lose sensitivity. Note that
if you average more pulses or ranges, then the threshold level
can usually be reduced.
SQI To optimize the SQI level, display velocity and select the
lowest value of the threshold that eliminates the display noise.
If the SQI level is set too high you lose sensitivity. In general,
you should see a greater area covered by velocity than
reflectivity since the velocity is more sensitive. If you do not,
you should reduce your SQI threshold. Note that if you
average more pulses or ranges, then the threshold level can
usually be reduced.
CCOR This is used to eliminate clutter targets that are very strong. It
should not be set to eliminate all clutter targets on a clear day
since this means that you are losing sensitivity. To optimize
the CCOR threshold it is best to know your system coherency
in terms of dB of clutter cancelation. Start at a value of 10 dB
greater (closer to 0) than this. Now display a PPI of dBZ at an
antenna elevation of approximately1 degree. The display
should be relatively clean of any clutter targets since most will
be rejected. Now reduce the CCOR (more negative) to
increase the number of clutter targets on the display until the
number of clutter targets does not increase. The optimum
value of the CCOR is approximately 5 dB more (closer to
zero) than this point. For example, if the number of clutter
targets is a maximum at -35 dB, then set the CCOR to
approximately - 30 dB. Note that your clutter filter selection
will effect the result.
SIG This should be done last. To optimize the SIG level, display
the width W and select the lowest value of the threshold that
eliminates the display noise. If the SIG level is set too high
you lose sensitivity. If you average more pulses or ranges,
then the threshold level can usually be reduced.
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