Messages from Usenet group comp.lang.idl-pvwave, compiled by Paulo Penteado
Struan Gray <struan.gray@sljus.lu.se> writes: > David Fanning, davidf@dfanning.com writes: >> Does anyone know off-hand the formula for converting nautical >> miles to degrees of latitude and longitude for a given >> latitude and longitude? Pointers to appropriate reference >> materials is also appreciated. > If I remember correctly, one nautical mile is defined as one > minute of latitude at the equator. My data book (Kaye and Laby > 14th Ed.) says one n.m. equals 1.852 km. > Struan Here's a pretty authoritative source, which gives 1 n.m = exactly 1.852 km. http://physics.nist.gov/cuu/Units/outside.html and also http://ts.nist.gov/ts/htdocs/230/235/appxc/$temp.htm which includes the following notation The international nautical mile of 1 852 meters (6 076.115 49...feet) was adopted effective July 1, 1954, for use in the United States. The value formerly used in the United States was 6 080.20 feet = 1 nautical (geographical or sea) mile. Note, by the way, that this is very close one minute of latitude at the equator if one assumes a circumference of exactly 40000 kilometers. In fact, the original definition of a meter was one ten-millionth of the distance from the equator to the North Pole along a meridian passing through Dunkirk and Barcelona, i.e. a quarter circumference of exactly 10000 kilometers. William Thompson
One nautical mile was defined to be one minute of arc on the earth's surface. So moving north or south, the displacement in degrees of latitude is (naut miles)/60. Since the lines of longitude converge at the poles, the the displacement east or west in degrees of longitude is given by (naut miles)/(60*cos(latitude)). But how accurate must this be? The foregoing assumes a spherical earth, which is not quite true ... Cheers, Patrick Harrington In article <37D7E259.83B9EFB6@ssec.wisc.edu>, Liam Gumley <Liam.Gumley@ssec.wisc.edu> writes: |> David Fanning wrote: |> > Does anyone know off-hand the formula for converting nautical |> > miles to degrees of latitude and longitude for a given |> > latitude and longitude? Pointers to appropriate reference |> > materials is also appreciated. |> |> David, the following may prove helpful: |> |> According to my freshman physics text (Halliday and Resnick), 1 nautical |> mile = 1.852 kilometers. |> |> For computing the distance in kilometers between a pair of lat/lons, |> nothing beats the COMPASS routine from the ESRG library, available at |> |> http://www.astro.washington.edu/deutsch-bin/idllibsrch?keywo rd=compass |> |> Cheers, |> Liam. |> |> -- |> Liam E. Gumley |> Space Science and Engineering Center, UW-Madison |> http://cimss.ssec.wisc.edu/~gumley
Struan Gray (struan.gray@sljus.lu.se) writes: > If I remember correctly, one nautical mile is defined as one > minute of latitude at the equator. My data book (Kaye and Laby > 14th Ed.) says one n.m. equals 1.852 km. Duh. I've got to get better reference material. :-( Thanks, David -- David Fanning, Ph.D. Fanning Software Consulting Phone: 970-221-0438 E-Mail: davidf@dfanning.com Coyote's Guide to IDL Programming: http://www.dfanning.com/ Toll-Free IDL Book Orders: 1-888-461-0155
David Fanning wrote: > Does anyone know off-hand the formula for converting nautical > miles to degrees of latitude and longitude for a given > latitude and longitude? Pointers to appropriate reference > materials is also appreciated. David, the following may prove helpful: According to my freshman physics text (Halliday and Resnick), 1 nautical mile = 1.852 kilometers. For computing the distance in kilometers between a pair of lat/lons, nothing beats the COMPASS routine from the ESRG library, available at http://www.astro.washington.edu/deutsch-bin/idllibsrch?keywo rd=compass Cheers, Liam. -- Liam E. Gumley Space Science and Engineering Center, UW-Madison http://cimss.ssec.wisc.edu/~gumley
David Fanning, davidf@dfanning.com writes: > Does anyone know off-hand the formula for converting nautical > miles to degrees of latitude and longitude for a given > latitude and longitude? Pointers to appropriate reference > materials is also appreciated. If I remember correctly, one nautical mile is defined as one minute of latitude at the equator. My data book (Kaye and Laby 14th Ed.) says one n.m. equals 1.852 km. Struan
> Does anyone know off-hand the formula for converting nautical > miles to degrees of latitude and longitude for a given > latitude and longitude? Pointers to appropriate reference > materials is also appreciated. Yikes! Ol' Miss Buchanan is rolling in her grave! Pointers *are* appreciated. :-) Cheers, David -- David Fanning, Ph.D. Fanning Software Consulting Phone: 970-221-0438 E-Mail: davidf@dfanning.com Coyote's Guide to IDL Programming: http://www.dfanning.com/ Toll-Free IDL Book Orders: 1-888-461-0155