Convert NC Grid to LatLng

grid2LatLng.js

/*

Usage: var convertedGrid = gridToLatLng("3542A8115A");
Returns: 
{ sw: [ 35.7125, -81.2625 ],
  se: [ 35.7125, -81.26666666666667 ],
  ne: [ 35.71666666666667, -81.26666666666667 ],
  nw: [ 35.71666666666667, -81.2625 ] }
  

Grids in NC are 1/4(.25) seconds square.  The grid notation is the encoded southwest corner of a .25 second square.

This may not be useful outside of NC 811.

Credit for reverse engineering goes to AH.

*/

function gridToLatLng(grid){
		String.prototype.replaceArray = function(find, replace) {
			var replaceString = this;
			var regex; 
			for (var i = 0; i < find.length; i++) {
				regex = new RegExp(find[i], "g");
				replaceString = replaceString.replace(regex, replace[i]);
			}
			return replaceString;
		};

		grid = grid.replaceArray(["D","C","B","A"],
			["00","15","30","45"]);

		var t = [];
		for(var x = 0; x<grid.length; x+=2){
			t.push(grid.substr(x, 2));
		}

		var lat = t.splice(0, t.length/2);
		var lng = t;
		for (var i in lat){
			lat[i] = parseFloat(lat[i]);
		}
		for (var i in lng){
			lng[i] = parseFloat(lng[i]);
		}

		var step = 15/3600;

		lat = lat[2]/3600 + lat[1]/60 + lat[0];
		lng = -(lng[2]/3600 + lng[1]/60 + lng[0]);
		
		var sw = [lat, lng];
		var se = [lat, lng - step];
		var nw = [lat + step, lng];
		var ne = [lat + step, lng - step];

		return {"sw":sw, "se":se, "ne":ne, "nw": nw};

}