GoogleMap地图的解析

    最近需要做一个离线地图的项目，然后找地图，最后确定从Google那边得到地图切片，然后就准备着手做了，Google地图的编号一开始不知到应该怎么做，后来查了资料之后，就尝试解方程了，最后用二分法找的解，效率不高，不过将就用了。下面是代码：

public class Main {
	/**
	 * @param args
	 * @param Google Map中将经纬度转换为图片编号的方法
	 * @author mikecoder
	 */
	public static void main(String[] args) {
		double LongDegree = 120.6395065;
		double LaDegree = 31.309066;
		int z = 19;
		int[] a = getGMapLocation(LongDegree, LaDegree, z);
		System.out.print(String.valueOf(a[0]) + ":" + String.valueOf(a[1]));
	}
	/**
	 * @param x y z
	 * @param x:为经度
	 * @param y:为纬度
	 * @param z:为缩放大小
	 */
	private static int[] getGMapLocation(double x, double y, int z){
		double tw,mapsize,origin,longdeg,longppd,longppdrad,longtiles,e;
		double pixelx,pixely;
		int tilex, tiley;
		tw = 256;  //每个小图的尺寸256×256(px)
		mapsize = tw * Math.pow((double)2, (double)z);
		origin = mapsize / 2;
		longdeg = Math.abs(180 + x);
		longppd = mapsize / 360;
		longppdrad = mapsize/(2*Math.PI);
		pixelx = longdeg * longppd;
		longtiles = pixelx  / tw;
		tilex = (int)longtiles;
		e = Math.sin((y)/180*Math.PI);
		if (e>0.9999) { e=0.9999; }
		if (e<-0.9999) { e=-0.9999; }
		pixely = origin + 0.5*Math.log((1+e)/(1-e)) * (-longppdrad);
		tiley = (int)(pixely / tw);
		//保存在这里
		int[] PNGNum = new int[2];
		PNGNum[0] = tilex;
		PNGNum[1] = tiley;
		return PNGNum;
	}
}