Great Circle Functions and Calculations

A great circle from Africa to Antarctic 6422 km

For more information about great circles and why they are used visit for example this link. The great circle distance is the shortest distance between any two points on a sphere.

Navigational Functions

There are four special navigational functions available, which will calculate great circle values on the sphere (Earth):

dist(lat1,lon1,lat2,lon2)
  -> distance from P1 to P2 in meters
	example:
	d1=dist(61.534,21.432, 62.325,21.467)
	[=87914.9667447436]

cog(lat1,lon1,lat2,lon2)
  -> COG at P1 in degr.
	example:
	heading=cog (61.534,21.432, 62.325,21.467)
	[=1.1773584522]

point(lat1,lon1,cog,dist)
  -> point at course and distance
	example:
	point(61.534,21.432, 90, 1000)
	[=(61.5339986965, 21.4508807761)]

midp(lat1,lon1,lat2,lon2)
  -> mid point between 2 points
	example:
	midp(61.534,21.432, 62.325,21.467)
	[=(61.9295011095, 21.4492734801)]

• Latitudes are given positive north in degrees
• Longitudes are given positive east in degrees
• COG is Course Over Ground 90-east and 180-south
• Distances are in meters on a sphere with earth radius

Conversion Functions

Two functions can be used to convert between degrees only and degrees, minutes and seconds formats:

   degr(d,m,s)
    -> result in degrees only
		example:
		degr(61,59,59)
		[=61.9997222222]

   dtoms(degr)
    -> shows minutes and seconds (m.m, s.s)
		example:
		dtoms(61.534)
		[=(32.0400000006, 2.4000000360)]