Description Usage Details Author(s) References Examples

Sets of precomputed grids that partition the Earth's surface into equal areas.

1 |

The available grids provide 50, 500, 5000, 10'000 and 20'000 equal area cells. The coordinates are given in radians. They can be converted into lat / lon decimal degrees using the code provided as an example.

Nils Arrigo, [email protected] 2012 EEB, the University of Arizona, Tucson

http://eqsp.sourceforge.net/ https://etna.mcs.kent.edu/vol.25.2006/pp309-327.dir/pp309-327.html

Leopardi, P. "A partition of the unit sphere into regions of equal area and small diameter" (2006). Electronic Transactions on Numerical Analysis 25:309-327.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | ```
#Converting grid50 (radians) to usual decimal degrees
data(grid50)
Rad2DD = function(lon, lat){
lonDD = 360 * round((lon / (2 * pi)), 5) - 180 + 0.01
latDD = 180 * round(lat / pi, 5) - 90 + 0.01
cbind(lonDD, latDD)
}
grid50DD = Rad2DD(grid50[,2], grid50[, 3])
grid50DD
#Converting decimal degrees to grid50 format (radians and properly centered)
DD2Rad = function(lon, lat){
lonrad = (lon + 180) * pi/180
latrad = (lat + 90) * pi/180
cbind(lonrad, latrad)
}
grid50Rad = DD2Rad(grid50DD[ ,1], grid50DD[ ,2])
grid50Rad = data.frame("1", grid50Rad) #this step is only cosmetic and necessary for compatibily issues.
grid50Rad
``` |

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