Vaisala RVP900, Руководство пользователя

Страница: 216 / 484

1. The most recent and the previous ray are used. For every valid point in the most recent
ray, the algorithm performs a search among the three nearest neighbors in the previous
ray to find a valid velocity. The search pattern is shown at the bottom of
Figure 46
(page 213) . This larger selection of alternate-PRF bins makes it more likely that the
algorithm finds the pairs of Low/High PRF data that are required for unfolding.
2. The unfolded velocities are subjected to standard 3x3 filtering.
7.5.3.2.2 Dual PRF, Random Phase Processing
In random phase processing, the "seam" at the start of the second trip is always
problematic, since the transmitter main bang and nearby clutter virtually always wipe out
the first few second trip range bins.
At a constant PRF, the second trip seam is always at the same range, but in dual PRF random
phase mode, the seam is different each ray.
Thresholded bins at the seam of the high PRF can be surrounded on either side by valid bins
taken at the low PRF.
The 3x3 filter has the effect of interpolating the reflectivity and width data over the bins at
the 2nd trip seam. Velocity data is also be filled-in using the nearest neighbor. The 2D filter
mitigates much of the damage that is caused at the 2nd trip seam to make a nearly seamless
display.
7.6 Reflectivity Calibration
The calculation of reflectivity described in 7.4.3 Reflectivity (page 200) . Here we look at its
derivation.
You can use the
Zauto utility to perform the calibration. See IRIS and RDA Utilities Guide .
7.6.1 Plot Method for Calibration of Io
This approach generates the curve (red) that determines the value of I
o
.
RVP900 User Guide M211322EN-J
214