Leaflet多段线点击点所属线段的PHP判断方法：基于航向角实现

<?php

/**
 * 计算两个地理坐标点之间的航向角（Bearing）。
 *
 * @param float $lat1 第一个点的纬度 (度)
 * @param float $lon1 第一个点的经度 (度)
 * @param float $lat2 第二个点的纬度 (度)
 * @param float $lon2 第二个点的经度 (度)
 * @return float 航向角 (0-360度)
 */
function calculateBearing($lat1, $lon1, $lat2, $lon2) {
    // 将度数转换为弧度
    $lat1 = deg2rad($lat1);
    $lon1 = deg2rad($lon1);
    $lat2 = deg2rad($lat2);
    $lon2 = deg2rad($lon2);

    // 计算经度差
    $dLon = $lon2 - $lon1;

    // 使用atan2函数计算航向角
    // y = sin(Δlon) * cos(lat2)
    // x = cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(Δlon)
    $y = sin($dLon) * cos($lat2);
    $x = cos($lat1) * sin($lat2) - sin($lat1) * cos($lat2) * cos($dLon);

    $bearingRad = atan2($y, $x);

    // 将弧度转换为度数，并归一化到0-360度范围
    $bearingDeg = rad2deg($bearingRad);
    return fmod(($bearingDeg + 360), 360);
}

// 示例用法：
// 假设多段线点为 A(51.691, -2.028), B(51.689, -2.024), C(51.690, -2.025)
// 假设点击点为 Click(51.690195, -2.025175)
// 假设最近点是 B(51.6898945656, -2.0241979535)

// 1. 计算从最近点B到C的航向角 (B -> C)
$bearing_B_to_C = calculateBearing(51.6898945656, -2.0241979535, 51.6909727036, -2.0277718088);
echo "Bearing from B to C: " . $bearing_B_to_C . " degrees\n"; // 示例输出：约154.17度 (实际应为 C 到 B 的反向，或者 B 到 C)

// 2. 计算从点击点到最近点B的航向角 (Click -> B)
$bearing_Click_to_B = calculateBearing(51.690195, -2.025175, 51.6898945656, -2.0241979535);
echo "Bearing from Click to B: " . $bearing_Click_to_B . " degrees\n"; // 示例输出：约154.61度

// 注意：这里需要根据实际的 A, B, C 点的顺序来调整计算。
// 如果多段线是 A -> B -> C，那么我们关心的是 B -> A 和 B -> C。
// 假设 A(51.692, -2.030), B(51.6898945656, -2.0241979535), C(51.6909727036, -2.0277718088)
// 那么 B 到 A 的航向角是 calculateBearing(B_lat, B_lon, A_lat, A_lon)
// B 到 C 的航向角是 calculateBearing(B_lat, B_lon, C_lat, C_lon)

// 实际应用中，需要一个函数来找到最近点及其前后点
function findClosestPointAndNeighbors($clickLat, $clickLon, $polylinePoints) {
    $minDist = PHP_FLOAT_MAX;
    $closestIndex = -1;
    $closestPoint = null;

    foreach ($polylinePoints as $index => $point) {
        // 简化距离计算，实际应用中可能需要更精确的Haversine公式
        $dist = sqrt(pow($clickLat - $point['lat'], 2) + pow($clickLon - $point['lon'], 2));
        if ($dist < $minDist) {
            $minDist = $dist;
            $closestIndex = $index;
            $closestPoint = $point;
        }
    }

    if ($closestIndex === -1) {
        return null;
    }

    $prevPoint = ($closestIndex > 0) ? $polylinePoints[$closestIndex - 1] : null;
    $nextPoint = ($closestIndex < count($polylinePoints) - 1) ? $polylinePoints[$closestIndex + 1] : null;

    return [
        'closest' => $closestPoint,
        'prev' => $prevPoint,
        'next' => $nextPoint,
        'closestIndex' => $closestIndex
    ];
}

// 示例多段线点
$polylinePoints = [
    ['lat' => 51.692, 'lon' => -2.030], // A
    ['lat' => 51.6898945656, 'lon' => -2.0241979535], // B
    ['lat' => 51.6909727036, 'lon' => -2.0277718088], // C
    ['lat' => 51.693, 'lon' => -2.032], // D
    ['lat' => 51.695, 'lon' => -2.035], // E
];

$clickLat = 51.690195;
$clickLon = -2.025175;

$neighbors = findClosestPointAndNeighbors($clickLat, $clickLon, $polylinePoints);

if ($neighbors) {
    $closestPoint = $neighbors['closest'];
    $prevPoint = $neighbors['prev'];
    $nextPoint = $neighbors['next'];

    echo "\nClosest point: (" . $closestPoint['lat'] . ", " . $closestPoint['lon'] . ")\n";

    $bearingClickToClosest = calculateBearing($clickLat, $clickLon, $closestPoint['lat'], $closestPoint['lon']);
    echo "Bearing (Click -> Closest): " . $bearingClickToClosest . " degrees\n";

    $tolerance = 5; // 允许的航向角误差范围

    if ($prevPoint) {
        $bearingClosestToPrev = calculateBearing($closestPoint['lat'], $closestPoint['lon'], $prevPoint['lat'], $prevPoint['lon']);
        echo "Bearing (Closest -> Prev): " . $bearingClosestToPrev . " degrees\n";
        // 判断点击点是否在 Closest -> Prev 方向
        // 由于航向角是单向的，Click->Closest 的方向应该与 Closest->Prev 的反向大致相同
        // 或者 Click->Closest 的方向与 Prev->Closest 的方向大致相同
        // Prev->Closest 的航向角
        $bearingPrevToClosest = calculateBearing($prevPoint['lat'], $prevPoint['lon'], $closestPoint['lat'], $closestPoint['lon']);
        echo "Bearing (Prev -> Closest): " . $bearingPrevToClosest . " degrees\n";

        if (abs($bearingClickToClosest - $bearingPrevToClosest) < $tolerance ||
            abs($bearingClickToClosest - $bearingPrevToClosest - 360) < $tolerance ||
            abs($bearingClickToClosest - $bearingPrevToClosest + 360) < $tolerance) {
            echo "Click is likely between previous point and closest point (e.g., A-B segment).\n";
        }
    }

    if ($nextPoint) {
        $bearingClosestToNext = calculateBearing($closestPoint['lat'], $closestPoint['lon'], $nextPoint['lat'], $nextPoint['lon']);
        echo "Bearing (Closest -> Next): " . $bearingClosestToNext . " degrees\n";

        $bearingNextToClosest = calculateBearing($nextPoint['lat'], $nextPoint['lon'], $closestPoint['lat'], $closestPoint['lon']);
        echo "Bearing (Next -> Closest): " . $bearingNextToClosest . " degrees\n";

        if (abs($bearingClickToClosest - $bearingNextToClosest) < $tolerance ||
            abs($bearingClickToClosest - $bearingNextToClosest - 360) < $tolerance ||
            abs($bearingClickToClosest - $bearingNextToClosest + 360) < $tolerance) {
            echo "Click is likely between closest point and next point (e.g., B-C segment).\n";
        }
    }

    // 如果点击点在多段线的起点或终点，只有一个方向可供比较。
    if (!$prevPoint && $nextPoint) {
        echo "Closest point is the start of the polyline.\n";
    } elseif ($prevPoint && !$nextPoint) {
        echo "Closest point is the end of the polyline.\n";
    }
} else {
    echo "No polyline points found or an error occurred.\n";
}

?>