View source: R/sl.triag.area.R
sl.triag.area | R Documentation |
Compute the area of a triangle on a sphere.
sl.triag.area(lon, lat)
lon |
a vector of length 3 specifying the longitudes of the triangle vertices. |
lat |
a vector of length 3 specifying the longitudes of the triangle vertices. |
This function is based on Girard's theorem: the area of a triangle on a unit sphere equals the excess of the sum of angles over pi
(180 degrees).
A scalar giving the area of the triangle (on a unit sphere).
This function is more accurate for large triangles but less accurate for small ones compared to sl.smalltriag.area
. Also, sl.smalltriag.area
is computationally cheaper, so for small triangles (<1/100 degrees or so), sl.smalltriag.area
should be preferred in any case.
Helge Goessling
sl.smalltriag.area
, sl.polygon.area
sl.triag.area(c(0,60,30),c(0,0,30))
## Should return:
## [1] 0.2866951
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