total of 10 pages only may be xeroxed - Memorial University's Digital ...

the dominant, or 9-, peaks of the spectrum have to he isolated, the data analpis
method h one of peak detection. These peak frequency pmitions were determined
from the spectra of eaeh mgaazimuth "all "sing the f0ll0~ steps:
1. A 150 emls window was placed about *fb such that the two frequencies wizh
greatest spectral po- muld be ~solated. These two peaks are the signals of interest
since they will typically be due to the Bragg waves if there h su5tient waw energy
for both components. If the radar frequency is 6.75 MHz then thjs corresponds to a
Doppler fqueney window of +0.0675 Ha about the Bragg huency. This window,
called the signal window, rvss ehmen to emre the detection of the largest expected
meat veloeitles in the experimental area (Pettie and Anderson [@I);
2. A noise Boor was calculated from the average power of all sign& in the region
0.5 Hz < Iq c 1.0 Hz where F is the Doppler frequency range. Because there are
potentially tan, Bragg sign& per radar spectrq one from the negative and pmltive
halves of the Doppler spectrum, this computation result9 in two signal and two noise
pmr measurements, one from either side of the spectrum;
3. The onasidd spectrum with the greatest signal-to-nohe ratio (SNR), of at
Least 10 dB, wan chaaen es the candidate spectrum for the current component esti-
mation; and
4. A moment calculation wa. performed by weighting the frequency components
in the signal windoar of the canmdate spectrum with the SNR dues to estimate the
central peak frequency. The SNR dues for each point used m the weighting had to
survive the minimum SNR threshold of 10 dB.
Thespectra from eafh radar cell ws subjected to the ahow pmcedure to generate
polar pi& of radial current data for each radar dateset. A sample plot of one of these
grids in shown in Figme 4.1. For display purposes each point on the grid is averaged
over a polar seetar of 20 km in range and 10' in azimuth.
period A m , Ine~pLIUlblel~lYIm hm thedata analysis may '81- mvwtlng thia mption. 41