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

oth of these techniques ean then be compared to the dts from thedrifteranalysis.
Both simulated and actual data will be subjected to the algorithm.
4.2 Drifter Data
Weighted splines were fitted to the northerly aod easterly errordinates of each driner
track to form an evenly spaced time series, with t he hour inten*, of position and
velocity rn described by Helbig (491. Weights were chosen to he inversely proportional
to the &mated quality of each pasitional Ex. s supplied by Senice Arga. The
data were not low-pass atered and extensive simulations by Helbig (491 indicated the
rdtant rpeeds exhibited standard dwiations of about 5-7 m/s.
The gist of the drifter velocity calculation is to aerentiate the splined-fitted
pasitiaodd&a. It should be noted that although thespline 6ttio~ anddiEere~tI~ting
a intended to smooth irregularities from the drifter tracks, the deriwd velocities are
not eqwvalent to the radar results since they mntaio iaiormation at scds which may
be different than thase mewred by the radar. The drifter estimate is Lagrandan
in nature. glving an average due over a portion of a tradr. Howwer, the radar
meslue is Euleriao, being ao aver* estimate over the radar resolution cell, which
may he several square Idlometem. Therefore, the drifter and radar estimates may
never truly equate unless the current is uniform wer a region that is large, with
respect to the dimensions associated with both estimates. Hoover, this is the ody
Imown reliable technique to ted the radar cwent estimate since currents near the
s h e are extremely =cult to monitor.
4.3 Radar Data
Data from each radar beam direction was -pled at a rate of appmximately 1.7
Hz, as described in Section 2.2.2. This unambigously displays the spectral mntent
of the signal to apprmdmately f 0.8 Hz. which is su!Xcient for current measurement
39