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Draw a Circle

Draw a Circle

Draw a geographic circle using a GeoJSON polygon approximation.

const API_KEY = 'toursprung';

    function createGeodesicCircle(center, radiusKm, steps = 64) {
        const coords = [];
        for (let i = 0; i <= steps; i++) {
            const angle = (i / steps) * 2 * Math.PI;
            const dx = radiusKm / 111.32;
            const dy = radiusKm / (111.32 * Math.cos(center[1] * Math.PI / 180));
            coords.push([center[0] + dy * Math.sin(angle), center[1] + dx * Math.cos(angle)]);
        }
        return { type: 'Feature', geometry: { type: 'Polygon', coordinates: [coords] } };
    }

    const map = new maptoolkit.Map({
        container: 'map',
        style: `https://static.maptoolkit.net/styles/toursprung/terrain.json?api_key=${API_KEY}`,
        center: [11.39085, 47.27574],
        zoom: 11,
        attributionControl: { compact: false }
    });

    map.addControl(new maptoolkit.NavigationControl(), 'top-right');

    map.on('load', () => {
        const circle = createGeodesicCircle([11.39085, 47.27574], 5);

        map.addSource('circle', { type: 'geojson', data: circle });

        map.addLayer({
            id: 'circle-fill',
            type: 'fill',
            source: 'circle',
            paint: { 'fill-color': '#3887be', 'fill-opacity': 0.3 }
        });

        map.addLayer({
            id: 'circle-outline',
            type: 'line',
            source: 'circle',
            paint: { 'line-color': '#3887be', 'line-width': 2 }
        });
    });
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Draw a Circle – Maptoolkit Maps JS</title>
    <meta property="og:description" content="Draw a geographic circle using a GeoJSON polygon approximation." />
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <script src="https://unpkg.com/@maptoolkit/maps@11.0.0-beta.2/dist/maptoolkit.js"></script>
    <link rel="stylesheet" href="https://unpkg.com/@maptoolkit/maps@11.0.0-beta.2/dist/maptoolkit.css" />
    <style>
        html, body { width: 100%; height: 100%; margin: 0; padding: 0; }
        #map { width: 100%; height: 100%; }
    </style>
</head>
<body>
<div id="map"></div>
<script>
    const API_KEY = 'toursprung';

    function createGeodesicCircle(center, radiusKm, steps = 64) {
        const coords = [];
        for (let i = 0; i <= steps; i++) {
            const angle = (i / steps) * 2 * Math.PI;
            const dx = radiusKm / 111.32;
            const dy = radiusKm / (111.32 * Math.cos(center[1] * Math.PI / 180));
            coords.push([center[0] + dy * Math.sin(angle), center[1] + dx * Math.cos(angle)]);
        }
        return { type: 'Feature', geometry: { type: 'Polygon', coordinates: [coords] } };
    }

    const map = new maptoolkit.Map({
        container: 'map',
        style: `https://static.maptoolkit.net/styles/toursprung/terrain.json?api_key=${API_KEY}`,
        center: [11.39085, 47.27574],
        zoom: 11,
        attributionControl: { compact: false }
    });

    map.addControl(new maptoolkit.NavigationControl(), 'top-right');

    map.on('load', () => {
        const circle = createGeodesicCircle([11.39085, 47.27574], 5);

        map.addSource('circle', { type: 'geojson', data: circle });

        map.addLayer({
            id: 'circle-fill',
            type: 'fill',
            source: 'circle',
            paint: { 'fill-color': '#3887be', 'fill-opacity': 0.3 }
        });

        map.addLayer({
            id: 'circle-outline',
            type: 'line',
            source: 'circle',
            paint: { 'line-color': '#3887be', 'line-width': 2 }
        });
    });
</script>
</body>
</html>
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