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#11
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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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#12
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Calculating distance from Lat/Long
On Thu, 04 Dec 2003 13:20:40 -0800, "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 First, an explanatory note: inverse cos is also known as arc.cos or cos^-1 The great circle distance is given by Earth radius * arccos [cos Lat1* cos Lat2 * cos (Long1 - Long2) + sin Lat1 * sin Lat2] The Earth (equatorial) radius is 6378 km, or 3963 statute miles or 3442 NM. Does this help? (There are other formulae for the same result...) Brian Whatcott Altus OK |
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#13
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Calculating distance from Lat/Long
On Thu, 04 Dec 2003 13:20:40 -0800, "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 First, an explanatory note: inverse cos is also known as arc.cos or cos^-1 The great circle distance is given by Earth radius * arccos [cos Lat1* cos Lat2 * cos (Long1 - Long2) + sin Lat1 * sin Lat2] The Earth (equatorial) radius is 6378 km, or 3963 statute miles or 3442 NM. Does this help? (There are other formulae for the same result...) Brian Whatcott Altus OK |
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#14
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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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#15
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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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#16
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Calculating distance from Lat/Long
Fifty seven lurkers just headed for the Tylenols with their heads
spinning, feeling nauseated and dizzy....(c; I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... and GPS... On Fri, 05 Dec 2003 00:27:38 GMT, Brian Whatcott wrote: First, an explanatory note: inverse cos is also known as arc.cos or cos^-1 The great circle distance is given by Earth radius * arccos [cos Lat1* cos Lat2 * cos (Long1 - Long2) + sin Lat1 * sin Lat2] The Earth (equatorial) radius is 6378 km, or 3963 statute miles or 3442 NM. Does this help? (There are other formulae for the same result...) Brian Whatcott Altus OK Larry W4CSC NNNN |
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#17
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Calculating distance from Lat/Long
Fifty seven lurkers just headed for the Tylenols with their heads
spinning, feeling nauseated and dizzy....(c; I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... and GPS... On Fri, 05 Dec 2003 00:27:38 GMT, Brian Whatcott wrote: First, an explanatory note: inverse cos is also known as arc.cos or cos^-1 The great circle distance is given by Earth radius * arccos [cos Lat1* cos Lat2 * cos (Long1 - Long2) + sin Lat1 * sin Lat2] The Earth (equatorial) radius is 6378 km, or 3963 statute miles or 3442 NM. Does this help? (There are other formulae for the same result...) Brian Whatcott Altus OK Larry W4CSC NNNN |
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#18
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Calculating distance from Lat/Long
"Larry W4CSC" wrote in message ... Fifty seven lurkers just headed for the Tylenols with their heads spinning, feeling nauseated and dizzy....(c; I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... and GPS... Sounds like the old days with Oscar and his apples (to be polite). Oh... The is trig and not the sphere stuff..... Leanne |
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#19
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Calculating distance from Lat/Long
"Larry W4CSC" wrote in message ... Fifty seven lurkers just headed for the Tylenols with their heads spinning, feeling nauseated and dizzy....(c; I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... and GPS... Sounds like the old days with Oscar and his apples (to be polite). Oh... The is trig and not the sphere stuff..... Leanne |
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#20
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Calculating distance from Lat/Long
Not too surprising...I meant to mention that the inverse cos is
intended to provided an angle in *radians* 1 radian = 1 degree X 180/pi or about 57 degrees. Brian W On Fri, 05 Dec 2003 02:51:48 GMT, (Larry W4CSC) wrote: Fifty seven lurkers just headed for the Tylenols with their heads spinning, feeling nauseated and dizzy....(c; I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... I love my Nautical Almanac..... and GPS... On Fri, 05 Dec 2003 00:27:38 GMT, Brian Whatcott wrote: First, an explanatory note: inverse cos is also known as arc.cos or cos^-1 The great circle distance is given by Earth radius * arccos [cos Lat1* cos Lat2 * cos (Long1 - Long2) + sin Lat1 * sin Lat2] The Earth (equatorial) radius is 6378 km, or 3963 statute miles or 3442 NM. Does this help? (There are other formulae for the same result...) Brian Whatcott Altus OK Larry W4CSC NNNN |
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