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» Online Classroom   »   » Public Discussion of Cel Nav   » nautical mile

   
Author Topic: nautical mile
cuniverse


 - posted January 31, 2010 11:16 AM      Profile for cuniverse           Edit/Delete Post 
how do you calculate the nautical miles between
N15Deg 150W to N15Deg 165W on Latitudinal plain

David Burch


 - posted January 31, 2010 11:48 AM      Profile for David Burch           Edit/Delete Post 
"...N15Deg 150W to N15Deg 165W on Latitudinal plain"

we have various calculators online that do this, but the short answer on the same lat line, for a short distance it would be just (Lon difference in minutes) x cos (lat)= 15x60xcos(15) = 869.33 nmi.

this is essentially a mercator result. it would be 869.16 nmi by GC

do a search to find our NIMA calculators to check the latter.

note that for a longer distance the CG difference will be larger, esp at higher latitudes.

Also if you really want to do this most precisely, you have to use ellipsoidal distances that depend on the chart datum, and we have a calculator for that online somewhere as well.

From: Starpath, Seattle, WA
David Burch


 - posted January 31, 2010 11:55 AM      Profile for David Burch           Edit/Delete Post 
Remember too, that you can always find mercator or rhumbline distances by just using your dividers on a chart and walk off the distance. No math required at all.

and you could even do this with a universal plotting sheet if you did not have a chart of the region of interest.

From: Starpath, Seattle, WA


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