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SailTimer is a technology for sailboat navigation, which calculates optimal tacking angles, distances and times. Seafarers have had a dilemma for as long as sailboats could use lift to sail upwind.〔Chapter 5: The Wind and How It Makes a Sailboat Go. From: O'Day, George D. (1967). Sail in a Day!, Grosset & Dunlap Publishers, New York.〕〔(Points of Sail ) , SchoolofSailing.net, Burlington, VT USA. Viewed Dec. 27 2011.〕 Should you head off the wind more, to get more speed (but at a longer distance)? Or should you sail upwind more, to lessen the distance (but at slower speed)? Different sailboats have varying capabilities for sailing upwind〔(Sailing Upwind (Tutorial) ) , Leo Robbins Community Sailing Center, Ventura CA, USA. Viewed Dec. 18 2011.〕 because of the condition of their sails, the type of rigging, and the ability to track in the water based on their keel or centerboard design. That means there is not a single rule for everyone; each vessel has its own individual polar plot of boat speed for all of the possible wind angles.〔(Polar plot for Najad 505 ). Najad Yachts of Sweden. Viewed Dec. 18 2011.〕〔(Polar plot for Morris 29 ). Morris Yachts, Maine, USA. Viewed Dec. 18 2011.〕 The mathematical calculations for determining the tacking angles and times with polar plots would not be practical to do mentally. ==Rationale== Civilian access to GPS navigation became available circa 1989. Estimated time of arrival (ETA) is a standard GPS chartplotter parameter, based on the assumption that the route will be a straight line to the destination. However, sailboats typically tack back and forth, creating a longer distance than a straight line.〔(Bad News for "Velocity Made Good" ): GAM on Yachting magazine, Toronto, Canada, May–June 2009, pp. 26-30. (836k PDF)〕 SailTimer evaluates tacking distances and boat speeds on different points of sail to determine optimal tacking headings. During the original development of the SailTimer software in 2005-2006,〔(2006 Press Releases ). History of product announcements for SailTimer Inc. at SailTimerInc.com, Viewed Dec. 18 2011.〕 the term TTD (tm) was coined for "Tacking Time to Destination". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「SailTimer」の詳細全文を読む スポンサード リンク
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