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Not necessarilly. Great Lake charts are in statute miles and use Poly
Conic projection, rather than the Mercator that the off shore charts use. Reply ******************** An exception somewhat proving the rule. I'm not familiar with charts for the Great Lakes, of course, but it's surprising they wouldn't follow the convention of the majority of the world. Do Great Lakes sailors discuss vessel speed or wind speeds in knots or MPH? ================================== I'm told that the Lakes use statute miles because of the land mass involved in the charts. However, had the St. Lawrence Seaway came into being sooner, bringing "salties" to the Lakes, the chartmakers might have decided to use the "off-shore" type of chart and nautical miles to avoid confusion. As far as speed terminology, you hear both. |
On Fri, 15 Apr 2005 10:33:48 -0400, Black Dog
wrote: and occasionally some drunken lubber will throw in KPH too ========================== Personally I've always had a preference for furlongs per fortnignt. |
On Fri, 15 Apr 2005 15:05:11 -0400, Wayne.B
wrote: On Fri, 15 Apr 2005 10:33:48 -0400, Black Dog wrote: and occasionally some drunken lubber will throw in KPH too ========================== Personally I've always had a preference for furlongs per fortnignt. I always thought cubits per parsec was a good method. Later, Tom |
On Fri, 15 Apr 2005 21:21:22 GMT, Gene Kearns
wrote: On Fri, 15 Apr 2005 20:15:02 GMT, Short Wave Sportfishing wrote: On Fri, 15 Apr 2005 15:05:11 -0400, Wayne.B wrote: On Fri, 15 Apr 2005 10:33:48 -0400, Black Dog wrote: and occasionally some drunken lubber will throw in KPH too ========================== Personally I've always had a preference for furlongs per fortnignt. I always thought cubits per parsec was a good method. Let it go, guys.... this is getting too close to how long you taught your wife a foot was... Um... ¿Que? |
On Fri, 15 Apr 2005 19:12:36 GMT, Red Cloud©
wrote: The windspeed during the storm was increasing by roughly 3 KPH! ============================================ In Europe it is very common to measure wind speed in meters per second. There is a handy conversion however taught to me by a Swede who used to crew on my former racing boat. If you double meters per second, it is almost exactly equal to knots. Try it, it works. |
On Wed, 13 Apr 2005 13:51:46 -0400, "The real ME"
wrote: In another posts someone asked questions concerning nautical terms. A knot is what you put in a line (not a rope), a MPH is a speed measurment. |
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My only point was that there IS a correct way to use the term "KPH",
although it is frequently used incorrectly. "Knots" includes an implied "per hour", so the only time you would add "Per Hour" after knots, (KPH) would be to describe by how much speed something (wind, boat, dolphins) was increasing or decreasing on average referenced to an elapsed hour. rusty redcloud *********** "Knots per hour" is an incorrect usage. Since a 1 knot speed is equal to a nautical mile per hour, some people might wonder why they are spelled differently. "Knot" isn't a misspelling of "naut". Using knots to measure speed dates back to the days of sail. A midshipman or the quartermaster would be required to measure the speed of a vessel at regular intervals, make a note of it in a log, and make report to the master and/or navigator. To measure speed, a wooden, wedge-shaped board (speed log) was tossed overboard. A spooled line would be attached to the board, and the line would be allowed to pay out as the board was left in the vessel's wake. The line payed out for a short but precisely measurable period of time. (A short interval sand glass would have been used) A series of knots were tied in the line at known intervals, and the seaman measuring the speed would count the number of knots that slipped through his fingers during the measuring period. Speed would be reported as "eight knots" if eight knots slipped though the fingers of the party doing the measuring. The math is simple, but ingenious. The time interval will be a specific portion of an hour. Say for example the measuring exercise took place for 30 seconds after the "log" splashed down- that would be 1/120th of an hour. If the knots were tied in the line 1/120th of a nautical mile (about 47 and 1/4 feet) apart then at 1 nautical mile per exactly 1 "knot" would pay out during the measuring. If 6 X approx 47 1/4 feet payed out in 30 seconds, then the vessel would cover six nautical miles in an hour, or be making a speed of six knots. |
A boat was traveling at 5 knots. It speeds up gradually at a rate of 2
Knots per Hour. ******************** A vessel's speed may be recorded at specific periods of time, but nobody familiar with the movement of a boat that is effected by winds, currents, etc would presume that the change had been, or even likely would be, evenly graduated over a period of time. If you boat is making 5 knots at 0500 and 11 knots at 0800, that doesn't mean that it sped up at a rate of 2 knots per hour. It is entirely possible that the boat didn't speed up until 0759, when the wind shifted. |
Here's a new term to keep you confused: AVERAGE
sheesh! rusty redcloud ********* Thank you. Here's one for you, as well. NAVIGATION There is no navigational use for determining the average hourly change in knots during a previous period of time. It cannot be used to forecast future changes, will almost certainly be non-linear, and could lead to some wildly erroneous conclusions about position. It is common to project present speed, particularly for short intervals, to predict future position. How fast you were running yesterday, or even several hours ago becomes meaningless. The average rate of hourly change in knots made would be useful for evaluating tits on a boar. |
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