Vaisala RVP900

Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 231
area, it is recommended that you switch both speckle filters off. When
either speckle filter is switched on, it is applied in HydroClass.
6.4.3.2 2D 3x3 Speckle Filter
The 2D 3x3 speckle filter examines three adjacent range bins from three
successive rays, in order to assign a value to the center point. Thus, for each
output point, its eight neighboring bins in range and time are available to
the filter. Only the dBZ, dBT, Velocity, and Width data are candidates for
this filtering step; all other parameters are processed using the default 1D
speckle filter.
The rules for the 2D 3x3 speckle filter are as follows:
The 2D 3x3 filter performs two functions:
- Filling by interpolation
- Thresholding of isolated noise bins
Some examples are shown graphically in the Figure 48.
Center Point Action
Assign Threshold Else
Valid Center Point If there are none or only
one other valid point in
the 3x3.
Do Nothing. Pass the
center point value as-is.
Thresholded Center Point If there are five or fewer
valid neighbors in the
3x3.
If there are six or more
valid neighbors in the
3x3, average to fill the
center point.