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gential component estimate, wen with the observed errors the technique may stili be useiul for the estimation of the mean tangential component over large regions. The results for the cmes considered produced a large relative error, but it is apparent from the scattergrams and the correlation eoaeients that the statistical results indicate a better 6t as the azimuthal extent is inere&. Better results may certainly he obtained if the outstanding issues mentioned in the abwe parwaph were resolved Horn, the validity of this estimate may ultimately depend on the current variability in the reeon, which hap not been eonsidered here. If the W que ean pmvide a mean current estimate capability for Large oceanic sectors, it is still quite a usefui result since this parameter can't he estimated, in real-time, by other systems. ID condwion, heeavse of the following unlm-: Degree of current uniformity about drifter estimate; . Possible non-tionary currents within beam switching intervals; and Possible beamforming prohi- the performance of the vector current algorithm has not been rigorously established. Horn, the slmulatioos suggest this parameter can be easily estimated to within one standard deviation of the drifter and radar velocity distributions under uniform current conditions. 6.3 Discussion Since the -tor current algorithm sense. the radial current change over azimuth to estimate the other orthogonal current component, the extent of this azimuth in relation to the radar beamwidth is an important parameter. Obviously, this extent should resect the extent of the uniform nurent won. Ciearly then, as this extent decreases, the radar pedormance is dependent on the 'narrmess' of the receiving 77
eam for spatial selectivity. Optimally, each beam synthesized by the radar should isaiate a differrot mdu scattering area, or 'pi-piece' from the radar coverage zone such that the number of adjaeent be-, and hence the region size, is kept to a midmum If the extent is too large, the risk of using current data from a non-uniform region increases. The resolving paruer of any radar syaem is dependent on its ability to distinguish between multiple targets within a radar scattering cell. Howew, for currents there is only one fundamental target, that being ocean .naves that are matched to the radar carrier via the Bragg phenomena. The mean current is indirectly seared by thir mechanism for each radar eeU. Theretore, the cell size is a measure of the spatial resolution of a current meemring HF radar. Since the sector used for wetor went stimation consists of anumber of these cells, from a least squares perspective, as this number increases better estimates of the mean current may be expected. Further, the size of tlus number is a function of the radar system parameters Jueh as antenna hemwidth and radar bandwidth, which de6ne the are and radial extents, respectively, of the cell. Therefmore, in the design phase of a current measuiog radar system, these parameters must he carefully selected, based on the knowledge of the current @mes which are to be monitored. For the estimation of wetor currents at long rangen it b n-sary to synthesize very narrow beams. This may not be practical at eoartal sites because at HF they requM antenna arrays which are hundreds of meters in length. Hence, for a practicd system, if the beamwidth is not adequate to estimate 6ne scale current measurements at long ranges it may be necmary to provide a second station to sense the current 6dd from another direction. Howewr, if a 6naresolutian onestation system, which overcomes the aperture Limitations of a linear array, mn be developed, the method presented here may provide a framework for a praetieal real-time w ent monitoring system. 78
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CENTRE FOR NEWFOUNDLAND STUDIES TOT
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Abstract Esrlm=r#oo of ocean surf-
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Acknowledgements Quite a number of
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Contents Abstract List of Figures L
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5.2 Direct Radial Surface Current C
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3.4 System architecture of Cape Rae
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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
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southward. In t k example the same
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1.2 Conventional Methods for Measur
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iceberg motion, a better relationsh
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magnitude of the radid component is
Page 30 and 31:
Rice 1241, Barrick [I] developed an
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ange broad and narrow-ham systems (
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the shon-r- radar is quite diEerent
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of a chapter. Thig dso provides an
Page 38 and 39:
2.2 Radial Surface Currents 2.2.1 T
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Figure 2.1: Radw Spectrum (solid li
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intervals of Ar and A.9, where thee
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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 66 and 67: 4.6.2 Selection of Algorithmn Param
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 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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