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Editorial Team
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Asked: 2026-06-06T03:59:41+00:00

Is it possible to detect if the visible map display more than one time

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Is it possible to detect if the visible map display more than one time the earth

For example, if Australia is visible twice or more like in zoom = 0

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1 Answer

  1. Editorial Team

    So the Google Maps displays textures with a resolution of 256 x 256. So at zoom level 0 you need a map canvas of 256+1 pixels wide or greater for the texture to wrap (or repeat). At zoom level 1 this doubles to 512+1, at zoom level 2 1024+1, etc.

    This coding example puts a little text under the map to say whether the original width of the world (256 * 2 ^ zoom level) is wrapping based on the width of the canvas. If your canvas is 800 px width, then at zoom levels 0 & 1 your map will wrap, at zoom level 2 (which requires a minimal canvas width of 1024+1) your map is not wrapping. 

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <script src='http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js' type='text/javascript'></script>
    <script type="text/javascript"></script>
</head>
<script type="text/javascript" src="http://maps.google.com/maps/api/js?sensor=false"></script>
<script type="text/javascript">

var map;
var mapWidth;
var mapTextureSize = 256;

function initialize()
{
    var latlng = new google.maps.LatLng(0, 0);
    map = new google.maps.Map(document.getElementById('map'), {
      zoom:0,
      center:latlng,
      mapTypeId:google.maps.MapTypeId.SATELLITE
    });

    google.maps.event.addListener(map, 'zoom_changed', checkZoom);

    mapWidth = document.getElementById('map').style.width;
    mapWidth = parseInt(mapWidth.substr(0, mapWidth.length-2));

    checkZoom();
}

function checkZoom()
{
    var result = mapTextureSize * Math.pow(2,map.zoom);
    if (result + 1 > mapWidth)
    {
        document.getElementById('feedback').innerText = "no wrapping";
    }
    else
    {
        document.getElementById('feedback').innerText = "wrapping";
    }
}
</script>
<body onLoad="initialize()">
<div id="map" style="width: 800px; height: 350px;"></div>
<div id="feedback" style="width: 800px;"></div>
</body>
</html>
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