User manual

Code: ENIGMA III User Manual
Edition: 1 Revision: 4
Date: 19/12/2008
Page: 68/97
7.2 Reflectivity.
The corrected reflectivity is calculated by the formula:
Z =SNR dBZ
0
20⋅logr a⋅rCCOR A
R
where:
SNR is a signal-to-noise ratio, calculated by the formula:
SNR=10⋅log
T
0
−N
N

;
T
0
is calculated in the autocorrelation algorithm.
The noise power N is calculated in the noise sampling procedure or in the adaptive noise sampling
algorithm. N of the noise sampling is stored in the following parameter:
SNR value is compared with the parameter 'NOISEThreshold' to eliminate values below the threshold.
7.3 Signal quality index (SQI)
SQI is a normalized magnitude of the first lag of autocorrelation.
SQI =
∣ R1 ∣
R0
It is in the range of [0;1]. 0 is a white noise, 1 is a perfectly-correlated signal.
SQI value is compared with the parameter 'SQIThreshold' to eliminate values below the threshold.
7.4 CCOR clutter correction
CCOR=10⋅log
S
ST
0
−R
0

S=
∣
R
1
∣
exp

2
⋅W
2
2

This value is compared with the parameter 'CCORThreshold' to eliminate values below the threshold.
7.5 Radial Velocity
Doppler velocity is calculated from the autocorrelation R
1
by formula:
V =
argR
1


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