Openlayers3中实现台风风圈绘制算法

概述：

台风的风圈的NE、NW、SW、SE四个方位的影响范围是不一致，本文介绍一种简单的风圈的绘制方法，并在OL3中展示。

实现效果：

实现代码：

1、数据格式

			var Configs = {
                CIRCLE_CENTER_X:104.21390114106414,
                CIRCLE_CENTER_Y:35.847595169932646,
                CIRCLE_R:{
                    "SE":0.5,
					"NE":0.3,
					"NW":0.2,
					"SW":0.5
				}
            };

2、关键代码

            var wkt = "POLYGON((";
            var wkt0 = "", _interval = 6;
            for(var i=0;i<360/_interval;i++){
                var _r = 0;
                var _ang = i*_interval;
                if(_ang>0&&_ang<=90){
                    _r = Configs.CIRCLE_R.NE;
                }
				else if(_ang>90&&_ang<=180){
                    _r = Configs.CIRCLE_R.NW;
				}
                else if(_ang>180&&_ang<=270){
                    _r = Configs.CIRCLE_R.SW;
                }
                else{
                    _r = Configs.CIRCLE_R.SE;
                }

                var x = Configs.CIRCLE_CENTER_X + _r * Math.cos(_ang * 3.14 /180);
                var y = Configs.CIRCLE_CENTER_Y + _r  * Math.sin(_ang * 3.14/180);

                wkt = wkt+""+x+" "+y+", ";
                if(i===0){
                    wkt0 = ""+x+" "+y+"";
				}
            }
            wkt = wkt+wkt0+"))";

3、完整代码

<html xmlns="http://www.w3.org/1999/xhtml">
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<title>Ol3 draw</title>
	<link rel="stylesheet" type="text/css" href="../../../plugin/ol3/css/ol.css"/>
	<style type="text/css">
		body, #map {
			border: 0px;
			margin: 0px;
			padding: 0px;
			width: 100%;
			height: 100%;
			font-size: 13px;
		}
	</style>
	<script type="text/javascript" src="../../../plugin/ol3/build/ol.js"></script>
	<script type="text/javascript" src="../../../plugin/jquery/jquery-1.8.3.js"></script>
	<script type="text/javascript">
		var wktformat = new ol.format.WKT();
		function init(){
			var untiled = new ol.layer.Image({
				source: new ol.source.ImageWMS({
					ratio: 1,
					url: 'http://localhost:8080/geoserver/lzugis/wms',
					params: {'FORMAT': 'image/png',
						'VERSION': '1.1.1',
						LAYERS: 'lzugis:province',
						STYLES: ''
					},
					serverType: 'geoserver'
				})
			});

			var Configs = {
                CIRCLE_CENTER_X:104.21390114106414,
                CIRCLE_CENTER_Y:35.847595169932646,
                CIRCLE_R:{
                    "SE":0.5,
					"NE":0.3,
					"NW":0.2,
					"SW":0.5
				}
            };
            var wkt = "POLYGON((";
            var wkt0 = "", _interval = 6;
            for(var i=0;i<360/_interval;i++){
                var _r = 0;
                var _ang = i*_interval;
                if(_ang>0&&_ang<=90){
                    _r = Configs.CIRCLE_R.NE;
                }
				else if(_ang>90&&_ang<=180){
                    _r = Configs.CIRCLE_R.NW;
				}
                else if(_ang>180&&_ang<=270){
                    _r = Configs.CIRCLE_R.SW;
                }
                else{
                    _r = Configs.CIRCLE_R.SE;
                }

                var x = Configs.CIRCLE_CENTER_X + _r * Math.cos(_ang * 3.14 /180);
                var y = Configs.CIRCLE_CENTER_Y + _r  * Math.sin(_ang * 3.14/180);

                wkt = wkt+""+x+" "+y+", ";
                if(i===0){
                    wkt0 = ""+x+" "+y+"";
				}
            }
            wkt = wkt+wkt0+"))";
            var features = new Array();
            features.push(wktformat.readFeature(wkt));
            features.push(wktformat.readFeature("POINT("+Configs.CIRCLE_CENTER_X+" "+Configs.CIRCLE_CENTER_Y+")"));

            var styleFunc = function(feature, resolution){
                var index = feature.get("index");
                return new ol.style.Style({
                    fill: new ol.style.Fill({
                        color: 'rgba(255, 0, 0, 0.2)'
                    }),
                    stroke: new ol.style.Stroke({
                        color: '#ffcc33',
                        width: 2
                    }),
                    image: new ol.style.Circle({
                        radius: 4,
                        fill: new ol.style.Fill({
                            color: '#ff0000'
                        })
                    })
                });
            };
			var vector = new ol.layer.Vector({
				source: new ol.source.Vector({
					features: features
				}),
				style:styleFunc
			});
			var map = new ol.Map({
				controls: ol.control.defaults({
					attribution: false
				}),
				target: 'map',
				layers: [untiled,vector],
				view: new ol.View({
					projection: new ol.proj.Projection({
						code: 'EPSG:4326',
						units: 'degrees'
					}),
					center: [103.847, 36.0473],
        			zoom: 4
				})
			});
		}
	</script>
</head>
<body onLoad="init()">
<div id="map">
</div>
</body>
</html>

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