Accuracy of Speed Trials on the Measured Mile
Résumé
Speed over the ground S is determined from observations of the time interval between the perpendicular crossing of two parallel lines of beacons, usually exactly one nautical mile apart. The combined effect of observational errors is investigated. It is shown that — contrary to a widely held opinion — these effects are not negligible. The required speed through the water V is determined by the usual method of taking the mean of means of at least 4 determinations of S on opposite courses. The reliability of this method of elimination of drift is not a subject of discussion in this News Letter; it is however shown that the standard error in V is considerably smaller than in each of the 4 determinations of S. Trials in daytime are to be preferred, because night trials are likely to be considerably less accurate. Other methods of speed trials are discussed in News Letter No. 27, 1958 (*).Téléchargements
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(i) References from Journals:
Anders, F.J. and Byrnes, M.R.(1991). “Accuracy of shoreline change rates as determined from maps and aerial photographs”, Shore and Beach, 59, pp. 17-26.
(ii) References from Books:
Foley, J.D., van Dam, A., Feiner, S. K. and Hughes, J.F. (1990), Computer Graphics – Principles and Practice, 2nd ed., Addison-Wesley, Reading, MA.
(iii) References from the technical material or research literature:
Smith, A. (1988). Colour photomapping. Report NRC-01-512. National Research Centre. Ottawa, Canada.
(iv) References from a web site:
desJardins, M. (2005). How to succeed in postgraduate study, Applied Ecology Research Group, University of Canberra, viewed 26 April 2009, http://aerg.canberra.edu.au/jardins.t.htm.
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