根据多边形的坐标点计中心点的方法

    var findCenter = function (points) {
        var point_num = points.length; //坐标点个数
        var X = 0, Y = 0, Z = 0;
        for(let i = 0; i< points.length; i++) {
            if (!points[i]) {
                continue;
            }
            let point = points[i];
            var lat, lng, x, y, z;
            lat = parseFloat(point.lat) * Math.PI / 180;
            lng = parseFloat(point.lng) * Math.PI / 180;
            x = Math.cos(lat) * Math.cos(lng);
            y = Math.cos(lat) * Math.sin(lng);
            z = Math.sin(lat);
            X += x;
            Y += y;
            Z += z;
        }
        X = X / point_num;
        Y = Y / point_num;
        Z = Z / point_num;

        var tmp_lng = Math.atan2(Y, X);
        var tmp_lat = Math.atan2(Z, Math.sqrt(X * X + Y * Y));
        return {lat:tmp_lat * 180 / Math.PI, lng:tmp_lng * 180 / Math.PI};
    }

var map = new BMapGL.Map('container');
var points = marker.getPath();
var center = findCenter(points);
var centerPoint = new BMapGL.Point(center.lng, center.lat);
var marker = new BMapGL.Marker(centerPoint);
map.addOverlay(marker1);