Circles

  • This example demonstrates how to create circles on a Google Map to represent populations in North America.

  • Circles are scaled based on city population data using a mathematical formula.

  • The map is centered on North America and uses a "terrain" map type.

  • The example uses JavaScript or TypeScript to define city data and create the map and circles with the Google Maps API.

This sample demonstrates using the Circle class to show approximate walking times between locations in Kyoto, Japan.

  • Select the needed distance from the menu.
  • Click the map to re-center the circle.
  • Drag the circle to reposition it.

The radii for the walking distances were calculated using the following formula: Distance = Speed x Time. For example, at a speed of 1.4 meters per second (approx. 3 mph), it takes a person approximately five minutes to walk 400 meters. The larger circles (15 and 30 minutes) were calculated using a slightly lower average speed to account for 'urban friction' — the delays caused by crosswalks, traffic lights, and crowds that accumulate over longer walks.

Read the documentation.

TypeScript

const mapElement = document.querySelector('gmp-map')!;
let innerMap: google.maps.Map;

async function init() {
    // Request needed libraries.
    const [{ Circle }, { AdvancedMarkerElement }, { event }] =
        await Promise.all([
            google.maps.importLibrary('maps'),
            google.maps.importLibrary('marker'),
            google.maps.importLibrary('core'),
        ]);

    // Set the initial map center point.
    const initialCenter = { lat: 34.98956821576194, lng: 135.74239981260283 }; // Hotel Emion, Kyoto, Japan

    // Get the inner map.
    innerMap = mapElement.innerMap;

    // Get the buttons.
    const buttons = document.querySelectorAll('input[name="radius"]');

    // Create the circle.
    const walkingCircle = new Circle({
        strokeColor: '#ffdd00ff',
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: '#ffdd00ff',
        fillOpacity: 0.35,
        map: innerMap,
        center: initialCenter,
        radius: 400,
        draggable: true,
        editable: false,
    });

    // Define a "Crosshair" vector icon
    const parser = new DOMParser();
    const svgString = `<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="-6 -6 12 12"><path d="M -6,0 L 6,0 M 0,-6 L 0,6" stroke="black" stroke-width="1"/></svg>`;

    const pinSvg = parser.parseFromString(
        svgString,
        'image/svg+xml'
    ).documentElement;

    const centerMarker = new AdvancedMarkerElement({
        position: initialCenter,
        title: 'A marker using a custom SVG image.',
        anchorLeft: '-50%',
        anchorTop: '-50%',
    });
    centerMarker.append(pinSvg);
    mapElement.append(centerMarker);

    // Wait for the map to finish drawing its tiles.
    event.addListenerOnce(innerMap, 'tilesloaded', () => {
        // Get the controls div
        const controls = document.getElementById('control-panel');

        // Display controls once map is loaded.
        if (controls) {
            controls.style.display = 'block';
        }
    });

    // Add event listener to update the radius based on user selection.
    buttons.forEach((button) => {
        button.addEventListener('change', (changeEvent) => {
            const target = changeEvent.target as HTMLInputElement;
            walkingCircle.setRadius(Number(target.value));
        });
    });

    // Handle user click, reset the map center and position the circle.
    innerMap.addListener(
        'click',
        (
            mapsMouseEvent:
                google.maps.MapMouseEvent | google.maps.IconMouseEvent
        ) => {
            const newCenter = mapsMouseEvent.latLng;
            if (!newCenter) return;
            walkingCircle.setCenter(newCenter);
            centerMarker.position = newCenter;
            innerMap.panTo(newCenter);
        }
    );

    // Handle user dragging the circle, update the center marker position.
    walkingCircle.addListener('center_changed', () => {
        centerMarker.position = walkingCircle.getCenter();
    });
}

void init();

JavaScript

const mapElement = document.querySelector('gmp-map');
let innerMap;

async function init() {
    // Request needed libraries.
    const [{ Circle }, { AdvancedMarkerElement }, { event }] =
        await Promise.all([
            google.maps.importLibrary('maps'),
            google.maps.importLibrary('marker'),
            google.maps.importLibrary('core'),
        ]);

    // Set the initial map center point.
    const initialCenter = { lat: 34.98956821576194, lng: 135.74239981260283 }; // Hotel Emion, Kyoto, Japan

    // Get the inner map.
    innerMap = mapElement.innerMap;

    // Get the buttons.
    const buttons = document.querySelectorAll('input[name="radius"]');

    // Create the circle.
    const walkingCircle = new Circle({
        strokeColor: '#ffdd00ff',
        strokeOpacity: 0.8,
        strokeWeight: 2,
        fillColor: '#ffdd00ff',
        fillOpacity: 0.35,
        map: innerMap,
        center: initialCenter,
        radius: 400,
        draggable: true,
        editable: false,
    });

    // Define a "Crosshair" vector icon
    const parser = new