T&T: compass calculations

[Peter Bennett]

Monday, September 21, 2009, 1:02:30 PM, Dickmasse wrote:

dcn> Greetings,  And I believe that would be nautical miles.

It is "units" - feet, metres, kilometres, furlongs, or whatever.


dcn>  
dcn> Dick
dcn> ----- Original Message -----
dcn> From: "Peter Bennett" <peterbb4 at interchange.ubc.ca>
dcn> To: "circumnavigate06" <circumnavigate06 at bellsouth.net>,
dcn> trawlers-and-trawlering at lists.samurai.com
dcn> Sent: Monday, September 21, 2009 3:46:26 PM GMT -05:00 US/Canada Eastern
dcn> Subject: Re: T&T: compass calculations

dcn> Monday, September 21, 2009, 12:28:53 PM, circumnavigate06 wrote:

c>> Hello,
c>>  
c>> There was a discussion in the marina this morning about a fellow that cruised
c>> from Charleston, SC to Bermuda and missed the islands entirely because his
c>> compass was not properly calibrated.  The next conversation of course, led to
c>> how many degrees you could be off course and still not miss Bermuda..
c>>  
c>> Well, I listened to all these professional cruisers conjure up their ideas and
c>> thought that it might not be safe to be on their boats!  I then realized that
c>> I also didn' lculating this and as we loop and cross
c>> Lake Michigan and other big bodies of water, including the big bend section of
c>> the Gulf, perhaps we all should take a few minutes and see what we really know
c>> about this and maybe when it comes to crossing big water, we will feel more
c>> comfortable knowing that we all can calculate these measurements.
c>>  
c>> So how about it Captains, what is the formula for calculating how many
c>> feet/meters/miles we are off for each degree of distance, at any distance
c>> away?
c>> Tommy

dcn> 1 in 60.

dcn> If you are off 1 degree, you will be off-course by 1 mile in 60 miles
dcn> (if I've remembered correctly)( this is only good for small angles,
dcn> perhaps up to 10 degrees or so.)




-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca