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4.6.2 Selection of Algorithmn Parameters For a single vector current estimate, radial current speeds tom a polar -tor of radar data are required, namely a Q-type sector as discused in Senion 2.3.1. Homer, determining the optimal size of thLn sector by ~peeifying the values of AR and A0 has been ao arbitrary aspect of the procedure at this stage. The emphaek has heen on algorithmn mrrectness as o ppd to optirmzation. Lo other words, algorithmn performance in the presence of a uoifouoifm current with added noise is the primary objective of this exercise. At this stage of the aigorithm development this b the simplest approach, since we wish to provide a comparative analysis between the radar and drifter methods with the m ption the drifter estimate is representative of the current in a Q-type senor in the vicimty of this estimate. However, it is pwsible that the oceanographic regimes about the drifter estimate aod the polar radar sector may not be the same. Since the algorithm requires, as input, radar data from a region wheh may be larger than the w on represented by the drifter estimate, it is unclear how the effeceets of a non-uniform current may bias the results. In the worst case scenario it is hoped the current estimate is indicative of the mean current in the region of interest. The problems associated with a conparison of this nature will be discused in the following section. 4.6.3 Algorithmn Constraints To perform a dehitive comparison between the radar and drifter estimates, the oceanographic regimes ssrociated with both estimates should coincide. This presents s problem whm the polar sector used by the vector current algorithmn issignificantly larger than the region in the vicinity of a drifter estimate. To apply the algorithmn we are assurmog the current b uniform in the sector. However, this may be true for only a small region about the drifter pwition. Ideally. this region Jhould span same porton of the drifter t rd. It should aLso be as smd as possible, such that the radar
vector current estimate is not distorted by radial components far removed h m the position of the driiter estimate. As the polar sector size is reduced the coneem noted in the abow parapaph do not exist or are not ss prominent. H m r , there are other issues to consider when this situation arise and there are a function of the radar's spatial parameters. For example, the anpllar extent of the seetor, A@, used by the vector m ent algorithm. will be affected by the number of be- required to span it. This may adversely dect the tangential component estimate if the ratio of this parameter to the radar beamwidth is not greater than two. This is apparent fram inspecting the general formulation equatioas in Section 2.3.1, sioee at leas two b- must span the region for the solution to he unique Thk &ect ia even more pronounced if the spectral resolution, and henee the current resalution, is too mme to sense the radial current change from beam to beam. The other extreme case is when the region size becorner too large. In thjs csse. ermrs m estimating the t-ntial current may be due to u nhm current miation throughout the region. In other words, the point estimate provided by the drifter data does not adequately repreent the mean evrrent of the region. For a consistent comparison each radar ertimate should be computed using data from a constant region size for each radarfdrifter estimate. This will amid any hiss as a result of variable spatial aver- in a comparison dataset. Far erample, the radar ediate from a sector of a hundred square !dometers wi!l consist d more range-azimuth cells, and hence more regression points, than an -timate from a few square kilometers. The validity of such a comparison holds only if the same c mnt e*sts owl both regions. Due to the inherent polar nature of the radar data, the radial point density is a function of range in that fewer points are aMtilable per unit area cs the range is increased. This is B result of the beamwidth of a directional antenna, since the are 48
Page 1:
CENTRE FOR NEWFOUNDLAND STUDIES TOT
Page 6 and 7:
Abstract Esrlm=r#oo of ocean surf-
Page 8 and 9:
Acknowledgements Quite a number of
Page 10 and 11:
Contents Abstract List of Figures L
Page 12 and 13:
5.2 Direct Radial Surface Current C
Page 14 and 15:
3.4 System architecture of Cape Rae
Page 16 and 17: List of Tables 5.1 Summary of stati
Page 18 and 19: List of Symbols d : Distance irom r
Page 20 and 21: Chapter 1 Introduction The monitori
Page 22 and 23: southward. In t k example the same
Page 24 and 25: 1.2 Conventional Methods for Measur
Page 26 and 27: iceberg motion, a better relationsh
Page 28 and 29: magnitude of the radid component is
Page 30 and 31: Rice 1241, Barrick [I] developed an
Page 32 and 33: ange broad and narrow-ham systems (
Page 34 and 35: the shon-r- radar is quite diEerent
Page 36 and 37: of a chapter. Thig dso provides an
Page 38 and 39: 2.2 Radial Surface Currents 2.2.1 T
Page 40 and 41: Figure 2.1: Radw Spectrum (solid li
Page 42 and 43: intervals of Ar and A.9, where thee
Page 44 and 45: Figure 2.3: Wan Q is mbdivided into
Page 46 and 47: The abwe system of equations is swe
Page 48 and 49: Chapter 3 Experimental Data 3.1 Int
Page 50 and 51: e built at other eoastd sites such
Page 52 and 53: Since the mean currents within mast
Page 54 and 55: Figure 3.4: System architecture of
Page 56 and 57: spatid variability and to check sys
Page 58 and 59: oth of these techniques ean then be
Page 60 and 61: the dominant, or 9-, peaks of the s
Page 62 and 63: modelled, since they are known quan
Page 64 and 65: Sine the drifter estimates m e mnst
Page 68 and 69: subtended by the b- increases in sb
Page 70 and 71: simplib the analysis by converting
Page 72 and 73: for then beams is therefore 3, 5 an
Page 74 and 75: with the graphs are from a linear r
Page 76 and 77: Fiere 5.2: Scattergrams of radid su
Page 78 and 79: Table 5.2 that the SNR eases of 10
Page 80 and 81: m-ments deliwred by radar and buoys
Page 82 and 83: Figure 5.6: Scattergrams of simulat
Page 84 and 85: Figure 5.7: Scattergrams of -tor me
Page 86 and 87: size. In other words, the algorithm
Page 88 and 89: tem, which is a programmable fsture
Page 90 and 91: Radii vetocify [cws) - Radar Figure
Page 92 and 93: ocean surface m nts where the curre
Page 94 and 95: Chapter 6 Conclusions 6.1 Direct Ra
Page 96 and 97: gential component estimate, wen wit
Page 98 and 99: One of the goals of this thesis has
Page 100 and 101: Future work dl also deal with the f
Page 102 and 103: [I4 D. Diemand, E. Faemer, and J. B
Page 104 and 105: (461 D. Barriek, M. Evans, and B. W
Page 106 and 107: DATE (LOCAL) EVENT Comments shorn 6
Page 108 and 109: TIME - DATE (LOCAL) EVENT Comments
Page 110 and 111: The tape was mated by using the DEC
Page 112 and 113: Where DATLOG - Array of 32x3 bytes
Page 114 and 115: Appendix C Catalogue of the NRSL Ra
Page 116 and 117:
Date (1992) 11/11 12/11 13/11 14/11
Page 118 and 119:
Time I FFT 1 - Date 01/11/92 02/11/
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