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#1
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Calculating distance from Lat/Long
Hi,
I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#2
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Calculating distance from Lat/Long
If you have a Bowditch, look under "Sailings" or look in Bowditch online for the same info. What you need will be in there. otn Lloyd Sumpter wrote: Hi, I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#3
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Calculating distance from Lat/Long
You want http://williams.best.vwh.net/avform.htm
"Lloyd Sumpter" wrote in message news  Hi, I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#4
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Calculating distance from Lat/Long
That will do it - thanks! Curious about how those formulae were developed, though... Lloyd On Thu, 04 Dec 2003 14:46:15 +0000, SpamJam wrote: You want http://williams.best.vwh.net/avform.htm "Lloyd Sumpter" wrote in message news Hi, I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#5
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Calculating distance from Lat/Long
"Lloyd Sumpter" wrote in message news That will do it - thanks! Curious about how those formulae were developed, though... I once tried to imagine Bowditch working and refining his tables and formulas manually. Must have been total dedication. Steve s/v Good Intentions Lloyd On Thu, 04 Dec 2003 14:46:15 +0000, SpamJam wrote: You want http://williams.best.vwh.net/avform.htm "Lloyd Sumpter" wrote in message news Hi, I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#6
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Calculating distance from Lat/Long
Lloyd Sumpter wrote:
That will do it - thanks! Curious about how those formulae were developed, though... Spherical Trigonometry - not for the fain of heart. -- Dan Best - (707) 431-1662, Healdsburg, CA 95448 B-2/75 1977-1979 Tayana 37 #192, "Tricia Jean" http://rangerbest.home.comcast.net/TriciaJean.JPG |
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#7
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Calculating distance from Lat/Long
It's an academic topic called "Spherical Geometry"
There is a plane which cuts the two coordinate pairs and the Earth center. A 'triangle' is drawn from the center and the two given points. The included angle is found from which the great circle distance is derived. Brian Whatcott On Thu, 04 Dec 2003 14:57:11 -0800, "Lloyd Sumpter" wrote: That will do it - thanks! Curious about how those formulae were developed, though... Lloyd On Thu, 04 Dec 2003 14:46:15 +0000, SpamJam wrote: You want http://williams.best.vwh.net/avform.htm "Lloyd Sumpter" wrote in message news Hi, I'm writing a program for Linux that displays position (from GPS) on a scanned-in chart, and would like it to calculate distance from current position to the cursor. How do you calculate distance between two points using lat/long? If they're due North/South, I can do it ( 1 minute of lat = 1 NM) but how do you calculate distance from longitude? Perhaps some formula based on the circumfrence of the Earth at the equator and the latitude? Lloyd Sumpter |
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#8
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Calculating distance from Lat/Long
Huh? The earth isn't flat? When did that happen? (tic)
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#9
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Calculating distance from Lat/Long
Dumb Ass! It's round. Kinda like a dinner plate. Be careful when you get
close to the edge. When Joshua Slocum was sailing around the world and meet a head of state in some island nation, that was the excepted explanation. Steve s/v Good Intentions |
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#10
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Calculating distance from Lat/Long
Dumb Ass! It's round. Kinda like a dinner plate. Be careful when you get
close to the edge. When Joshua Slocum was sailing around the world and meet a head of state in some island nation, that was the excepted explanation. Steve s/v Good Intentions |
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