计算地球表面以一点为中心指定距离为半径范围内的经纬度

private final static double DEF_PI = 3.14159265359; // PI
private final static double DEF_PI180 = 0.01745329252; // PI/180.0
private final static double DEF_R = 6370693.5; // radius of earth

/**
* 根据圆心、半径算出经纬度范围
* 
* @param lon	圆心经度
* @param lat	圆心纬度
* @param r  半径（米）
* @return double[4] 南侧经度，北侧经度，西侧纬度，东侧纬度
*/
public static double[] getRange(double lon, double lat, int r) {
	double[] range = new double[4];
	// 角度转换为弧度
	double ns = lat * DEF_PI180;
	double sinNs = Math.sin(ns);
	double cosNs = Math.cos(ns);
	double cosTmp = Math.cos(r / DEF_R);
	// 经度的差值
	double lonDif = Math.acos((cosTmp - sinNs * sinNs) / (cosNs * cosNs)) / DEF_PI180;
	// 保存经度
	range[0] = lon - lonDif;
	range[1] = lon + lonDif;
	double m = 0 - 2 * cosTmp * sinNs;
	double n = cosTmp * cosTmp - cosNs * cosNs;
	double o1 = (0 - m - Math.sqrt(m * m - 4 * (n))) / 2;
	double o2 = (0 - m + Math.sqrt(m * m - 4 * (n))) / 2;
	// 纬度
	double lat1 = 180 / DEF_PI * Math.asin(o1);
	double lat2 = 180 / DEF_PI * Math.asin(o2);
	// 保存
	range[2] = lat1;
	range[3] = lat2;
	return range;
}

/**
 * 计算地球面上两上坐标点之间距离
* @param lon1	位置1经度
* @param lat1	位置1纬度
* @param lon2	位置2经度
* @param lat2	位置2纬度
 */
public static double getLongDistance(double lon1, double lat1, double lon2, double lat2) {
	double ew1, ns1, ew2, ns2;
	double distance;
	// 角度转换为弧度
	ew1 = lon1 * DEF_PI180;
	ns1 = lat1 * DEF_PI180;
	ew2 = lon2 * DEF_PI180;
	ns2 = lat2 * DEF_PI180;
	// 求大圆劣弧与球心所夹的角(弧度)
	distance = Math.sin(ns1) * Math.sin(ns2) + Math.cos(ns1) * Math.cos(ns2) * Math.cos(ew1 - ew2);
	// 调整到[-1..1]范围内，避免溢出
	if (distance > 1.0) distance = 1.0;
	else if (distance < -1.0) distance = -1.0;
	// 求大圆劣弧长度
	distance = DEF_R * Math.acos(distance);
	return distance;
}

public static void main(String args[]) {
	double x1 = 13.957503;
	double y1 = 49.77837;
	double r[] = getRange(x1, y1, 100000);
	System.out.println(r[0]);
	System.out.println(r[1]);
	System.out.println(r[2]);
	System.out.println(r[3]);
	System.out.println(getLongDistance(x1, y1, r[0], y1));
	System.out.println(getLongDistance(x1, y1, r[1], y1));
	System.out.println(getLongDistance(x1, y1, x1, r[2]));
	System.out.println(getLongDistance(x1, y1, x1, r[3]));
}