使用谷歌地图API获取当前缩放级别的最大可视距离

我认为在实际范围内,而不是半径范围内,获得标记更容易、更准确。如果你愿意,你可以很容易地扩大或缩小界限。

Javascript:

var bounds = map.getBounds();
var sw = bounds.getSouthWest();
var ne = bounds.getNorthEast();

var s = sw.lat();
var w = sw.lng();
var n = ne.lat();
var e = ne.lng();

PHP/SQL:

$query = "SELECT * FROM Markers WHERE ";
if ($w > $e) { // If the bounds include the intl. date line
    $query .= "(lat BETWEEN $s AND $n) AND ((lng BETWEEN -180 AND $e) OR (lng BETWEEN $w AND 180))";
} else {
    $query .= "(lat BETWEEN $s AND $n) AND (lng BETWEEN $w AND $e)";
}

但是如果你真的想用半径法,你可以这样做:

var w = map.getBounds().getSouthWest().lng();
var centerLng = map.getCenter().lng();

var distance = centerLng - w; // This is the distance from the center to the left edge in degrees.