R2G2 (version 1.0-2)

grid50: Grids partitioning the surface of Earth into n equal areas.

Description

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

Usage

data(grid50)

Details

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.

References

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.

Examples

#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