earthquake-tools/tgbot/map_radius.html at master · mightymatth/earthquake-tools · GitHub

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<!-- don't remove this file, it's here for testing purposes -->

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Circle with Polygon Testing</title>

    <script src="https://maps.googleapis.com/maps/api/js?key=<YOUR_KEY_HERE>&callback=initMap"
            async></script>
    <script>
        const d2r = Math.PI / 180;   // degrees to radians
        const r2d = 180 / Math.PI;   // radians to degrees
        const earthRadius = 6371;   // in km

        function initMap() {
            // const hqPoint = {lat: 45.8293, lng: 15.9793}; // zagreb
            // const hqPoint = {lat: 64.9841821, lng: -18.1059013}; // iceland
            // const hqPoint = {lat: -36.852095, lng: 174.7631803}; // auckland, new zealand
            const hqPoint = {lat: 45.46, lng: 16.31}; // petrinja eq

            const points = 13
            const radius = 50 // km

            const map = new google.maps.Map(document.getElementById("map"), {
                zoom: 8,
                center: hqPoint
            });

            new google.maps.Marker({
                position: hqPoint,
                map: map
            });

            drawCircle(hqPoint.lat, hqPoint.lng, map, points, radius);
        }

        function drawCircle(lat, lng, map, points, radius) {
            // find the radius in lat/lon
            const latR = (radius / earthRadius) * r2d;
            const lngR = latR / Math.cos(lat * d2r);

            const latLngPoints = [];
            for (let i = 0; i < points + 1; i++) {
                const theta = Math.PI * (i / (points / 2));
                const ey = lat + (latR * Math.sin(theta)); // center b + radius y * sin(theta)
                const ex = lng + (lngR * Math.cos(theta)); // center a + radius x * cos(theta)
                latLngPoints.push({lat: ey, lng: ex});
            }

            new google.maps.Polyline({
                path: latLngPoints,
                strokeColor: '#000',
                strokeWeight: 2,
            }).setMap(map);
        }

    </script>

    <style>
        /* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
        #map {
            height: 100%;
        }

        /* Optional: Makes the sample page fill the window. */
        html,
        body {
            height: 100%;
            margin: 0;
            padding: 0;
        }
    </style>
</head>

<body>
<div id="map"></div>
</body>
</html>