# grid50: Grids partitioning the surface of Earth into n equal areas. In R2G2: Converting R CRAN outputs into Google Earth.

## Description

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

## Usage

 `1` ```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.

## Author(s)

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

## 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

 ``` 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 ```

R2G2 documentation built on May 29, 2017, 1:41 p.m.