package com.xiaopeng.itinerary.utils.map;
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public class FastDistanceCalculator {
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private static final double R = 6371.0; // 地球半径（千米）
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private static final double DEG_TO_RAD = Math.PI / 180.0;
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/**
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* 快速近似算法 - 性能极高，误差<0.5%
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* 适合需要大量计算的场景（如KNN、聚类）
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* 米
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*/
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public static double distanceFast(double lat1, double lon1,
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double lat2, double lon2) {
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try {
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double x = (lon2 - lon1) * DEG_TO_RAD * Math.cos((lat1 + lat2) * 0.5 * DEG_TO_RAD);
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double y = (lat2 - lat1) * DEG_TO_RAD;
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return R * Math.sqrt(x * x + y * y)*1000;
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}catch (Exception e){
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e.printStackTrace();
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}
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return 0;
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}
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/**
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* 快速近似算法 - 误差<0.5%
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* 适合需要大量计算的场景（如KNN、聚类）
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* 千米
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*/
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public static double distanceFastKm(double lat1, double lon1,
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double lat2, double lon2) {
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double x = (lon2 - lon1) * DEG_TO_RAD * Math.cos((lat1 + lat2) * 0.5 * DEG_TO_RAD);
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double y = (lat2 - lat1) * DEG_TO_RAD;
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return R * Math.sqrt(x * x + y * y);
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}
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/**
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* 平面近似 - 极高性能，适用于小范围（城市内）
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*/
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public static double distanceFlatApprox(double lat1, double lon1,
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double lat2, double lon2) {
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// 每度纬度约111km，每度经度随纬度变化
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double kmPerDegreeLat = 111.0;
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double kmPerDegreeLon = 111.0 * Math.cos((lat1 + lat2) * 0.5 * DEG_TO_RAD);
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double dLat = lat2 - lat1;
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double dLon = lon2 - lon1;
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return Math.sqrt(Math.pow(dLat * kmPerDegreeLat, 2) +
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Math.pow(dLon * kmPerDegreeLon, 2));
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}
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}
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