Vaisala IRIS - Figure 63 Radial Shear Algorithm Schematic

V
2
V
9
V
4
V
10
V
11
V
1
V
2
V
9
Gap > 0.5 *Range Filter Length
V
10
V
1
1/4
1/2
Convolve Triangular Filter
V
2
V
9
V
4
V
10
V
11
V
1
V~0 V~0
V’
1
V’
2
V’
9
V’
10
V
2
1
4
V
1
1
2
V
2
1
4
0
W
2
and
n
0 if V
n
is thresholded, else
n
1
where W
2
1
4
1
1
2
2
1
4
3
If the weight W is
1
2
, then bin is thresholded (eliminates speckle bins).
Input Radial Velocity Field
Reject V ~ 0 Bins
Difference Adjacent Bins
Filter and Smooth
Figure 63 Radial Shear Algorithm Schematic
Point Clutter Bin Removal
Point clutter bins produce erroneous high shear values when they are dierenced with
surrounding valid velocities. The first step in the shear algorithm is to remove obvious clutter
bins which were not canceled by the signal processor clutter filter. All velocity bins having a
velocity within 2 % of 0 velocity (as compared to the full velocity range) are tagged as
potential Clutter Bins. A Clutter Length Scale is defined as 1/3 of the Range Filter Length
value in km. Contiguous runs of Clutter Bins that are less than or equal to the Clutter Length
Scale are rejected.
IRIS Product and Display User Guide M211319EN-H
180 RESTRICTED