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WMS 时序渲染

发布于 2022-11-30 23:36:07 字数 4247 浏览 0 评论 0 收藏 0

本示例演示已缓存的 WMS 瓦片（tiled WMS）图层改变时间维度的时候，平滑的渲染图层。

本示例演示连续改变时间维度时，图层平滑的渲染。数据展示：IEM 生成的 NWS NEXRAD WSR-88D III级基础反射率的 CONUS 综合数据。

main.js

import 'ol/ol.css';
import Map from 'ol/Map';
import Stamen from 'ol/source/Stamen';
import TileLayer from 'ol/layer/Tile';
import TileWMS from 'ol/source/TileWMS';
import View from 'ol/View';
import {getCenter} from 'ol/extent';
import {transformExtent} from 'ol/proj';

function threeHoursAgo() {
  return new Date(Math.round(Date.now() / 3600000) * 3600000 - 3600000 * 3);
}

const extent = transformExtent([-126, 24, -66, 50], 'EPSG:4326', 'EPSG:3857');
let startDate = threeHoursAgo();
const frameRate = 0.5; // frames per second
let animationId = null;

const layers = [
  new TileLayer({
    source: new Stamen({
      layer: 'terrain',
    }),
  }),
  new TileLayer({
    extent: extent,
    source: new TileWMS({
      attributions: ['Iowa State University'],
      url: 'https://mesonet.agron.iastate.edu/cgi-bin/wms/nexrad/n0r-t.cgi',
      params: {'LAYERS': 'nexrad-n0r-wmst'},
    }),
  }),
];
const map = new Map({
  layers: layers,
  target: 'map',
  view: new View({
    center: getCenter(extent),
    zoom: 4,
  }),
});

function updateInfo() {
  const el = document.getElementById('info');
  el.innerHTML = startDate.toISOString();
}

function setTime() {
  startDate.setMinutes(startDate.getMinutes() + 15);
  if (startDate > Date.now()) {
    startDate = threeHoursAgo();
  }
  layers[1].getSource().updateParams({'TIME': startDate.toISOString()});
  updateInfo();
}
setTime();

const stop = function () {
  if (animationId !== null) {
    window.clearInterval(animationId);
    animationId = null;
  }
};

const play = function () {
  stop();
  animationId = window.setInterval(setTime, 1000 / frameRate);
};

const startButton = document.getElementById('play');
startButton.addEventListener('click', play, false);

const stopButton = document.getElementById('pause');
stopButton.addEventListener('click', stop, false);

updateInfo();

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>WMS Time</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <div role="group" aria-label="Animation controls">
      <button id="play" type="button">Play</button>
      <button id="pause" type="button">Pause</button>
      <span id="info"></span>
    </div>
    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "wms-time",
  "dependencies": {
    "ol": "7.1.0"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}

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