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Geographic Coordinates

发布于 2022-11-30 23:36:03 字数 4792 浏览 0 评论 0 收藏 0

Using geographic coordinates for the map view.

Calling the useGeographic function in the 'ol/proj' module makes it so the map view uses geographic coordinates (even if the view projection is not geographic).

main.js

import 'ol/ol.css';
import {Circle, Fill, Style} from 'ol/style';
import {Feature, Map, Overlay, View} from 'ol/index';
import {OSM, Vector as VectorSource} from 'ol/source';
import {Point} from 'ol/geom';
import {Tile as TileLayer, Vector as VectorLayer} from 'ol/layer';
import {useGeographic} from 'ol/proj';

useGeographic();

const place = [-110, 45];

const point = new Point(place);

const map = new Map({
  target: 'map',
  view: new View({
    center: place,
    zoom: 8,
  }),
  layers: [
    new TileLayer({
      source: new OSM(),
    }),
    new VectorLayer({
      source: new VectorSource({
        features: [new Feature(point)],
      }),
      style: new Style({
        image: new Circle({
          radius: 9,
          fill: new Fill({color: 'red'}),
        }),
      }),
    }),
  ],
});

const element = document.getElementById('popup');

const popup = new Overlay({
  element: element,
  positioning: 'bottom-center',
  stopEvent: false,
  offset: [0, -10],
});
map.addOverlay(popup);

function formatCoordinate(coordinate) {
  return `
    <table>
      <tbody>
        <tr><th>lon</th><td>${coordinate[0].toFixed(2)}</td></tr>
        <tr><th>lat</th><td>${coordinate[1].toFixed(2)}</td></tr>
      </tbody>
    </table>`;
}

const info = document.getElementById('info');
map.on('moveend', function () {
  const view = map.getView();
  const center = view.getCenter();
  info.innerHTML = formatCoordinate(center);
});

map.on('click', function (event) {
  const feature = map.getFeaturesAtPixel(event.pixel)[0];
  if (feature) {
    const coordinate = feature.getGeometry().getCoordinates();
    popup.setPosition(coordinate);
    $(element).popover({
      container: element.parentElement,
      html: true,
      sanitize: false,
      content: formatCoordinate(coordinate),
      placement: 'top',
    });
    $(element).popover('show');
  } else {
    $(element).popover('dispose');
  }
});

map.on('pointermove', function (event) {
  if (map.hasFeatureAtPixel(event.pixel)) {
    map.getViewport().style.cursor = 'pointer';
  } else {
    map.getViewport().style.cursor = 'inherit';
  }
});

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Geographic Coordinates</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>
    <script src="./resources/jquery-3.5.1.min.js"></script>
    <link rel="stylesheet" href="./resources/bootstrap.min.css">
    <script src="./resources/bootstrap.bundle.min.js"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
      td {
        padding: 0 0.5em;
        text-align: right;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map">
      <div id="popup"></div>
    </div>
    <div id="info"></div>

    <script src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "geographic",
  "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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