Wind Arrows

<!--
  示例：OpenLayers 风向箭头
  要点：RegularShape 组合出箭杆与箭头，按风速缩放、按风向旋转
  依赖：OpenLayers 10.3.1 · jsDelivr CDN
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
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<title>风向箭头</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.css">
<style>
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  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
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</head>
<body>
<div class="bar">
  <span>页面内气象观测数据</span>
  <span class="sep"></span>
  <span id="info">—</span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').textContent = 'OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net';
    return;
  }


  var reports = [
    {city: '北京', lon: 116.391, lat: 39.907, speed: 12, deg: 315},
    {city: '天津', lon: 117.200, lat: 39.084, speed: 9, deg: 20},
    {city: '石家庄', lon: 114.514, lat: 38.042, speed: 6, deg: 160},
    {city: '太原', lon: 112.549, lat: 37.857, speed: 14, deg: 280},
    {city: '济南', lon: 117.121, lat: 36.651, speed: 11, deg: 45},
    {city: '郑州', lon: 113.625, lat: 34.746, speed: 8, deg: 200},
    {city: '沈阳', lon: 123.431, lat: 41.805, speed: 16, deg: 330},
    {city: '呼和浩特', lon: 111.751, lat: 40.842, speed: 18, deg: 290},
    {city: '南京', lon: 118.797, lat: 32.060, speed: 5, deg: 120},
    {city: '上海', lon: 121.474, lat: 31.230, speed: 7, deg: 90},
    {city: '武汉', lon: 114.305, lat: 30.593, speed: 10, deg: 30},
    {city: '西安', lon: 108.940, lat: 34.341, speed: 13, deg: 250}
  ];

  var shaft = new ol.style.RegularShape({
    points: 2,
    radius: 6,
    stroke: new ol.style.Stroke({color: '#1f2b36', width: 2}),
    rotateWithView: true
  });

  var head = new ol.style.RegularShape({
    points: 3,
    radius: 5,
    fill: new ol.style.Fill({color: '#1f2b36'}),
    rotateWithView: true
  });

  var styles = [new ol.style.Style({image: shaft}), new ol.style.Style({image: head})];

  var features = reports.map(function (report) {
    var feature = new ol.Feature({
      geometry: new ol.geom.Point(ol.proj.fromLonLat([report.lon, report.lat])),
      wind: report,
      city: report.city
    });
    return feature;
  });

  var source = new ol.source.Vector({features: features});

  var vector = new ol.layer.Vector({
    source: source,
    style: function (feature) {
      var wind = feature.get('wind');
      var angle = ((wind.deg - 180) * Math.PI) / 180;
      var scale = wind.speed / 10;
      shaft.setScale([1, scale]);
      shaft.setRotation(angle);
      head.setDisplacement([0, head.getRadius() / 2 + shaft.getRadius() * scale]);
      head.setRotation(angle);
      return styles;
    }
  });

  var map = new ol.Map({
    target: 'map',
    layers: [
      new ol.layer.Tile({source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}), opacity: 0.7}),
      vector
    ],
    view: new ol.View({
      center: ol.proj.fromLonLat([116.5, 36.5]),
      zoom: 4
    })
  });

  map.on('pointermove', function (evt) {
    if (evt.dragging) {
      return;
    }
    var feature = map.forEachFeatureAtPixel(evt.pixel, function (candidate) {
      return candidate;
    });
    document.getElementById('info').textContent = feature
      ? feature.get('city') + ' · ' + feature.get('wind').speed +
        ' m/s · ' + feature.get('wind').deg + '°'
      : '—';
  });

})();
</script>
</body>
</html>