Display line that crosses 180th meridian
Draw a line across the 180th meridian using a GeoJSON source.
NPM module setup
npm install --save @maptiler/sdk
import { Map, MapStyle, config } from '@maptiler/sdk';
import '@maptiler/sdk/dist/maptiler-sdk.css';
config.apiKey = 'YOUR_MAPTILER_API_KEY_HERE';
const map = new Map({
container: 'map',
style: MapStyle.STREETS,
center: [-41.62667, 26.11598],
zoom: 0
});
map.on('load', function () {
map.addLayer({
'id': 'route',
'type': 'line',
'source': {
'type': 'geojson',
'data': {
'type': 'Feature',
'properties': {},
'geometry': createGeometry(false)
}
},
'layout': { 'line-cap': 'round' },
'paint': {
'line-color': '#007296',
'line-width': 4
}
});
map.addLayer({
'id': 'route-label',
'type': 'symbol',
'source': 'route',
'layout': {
'symbol-placement': 'line-center',
'text-field': 'Crosses the world'
}
});
map.addLayer({
'id': 'route-two',
'type': 'line',
'source': {
'type': 'geojson',
'data': {
'type': 'Feature',
'properties': {},
'geometry': createGeometry(true)
}
},
'layout': { 'line-cap': 'round' },
'paint': {
'line-color': '#F06317',
'line-width': 4
}
});
map.addLayer({
'id': 'route-two-label',
'type': 'symbol',
'source': 'route-two',
'layout': {
'symbol-placement': 'line-center',
'text-field': 'Crosses 180th meridian'
}
});
function createGeometry(doesCrossAntimeridian) {
const geometry = {
'type': 'LineString',
'coordinates': [
[-72.42187, -16.59408],
[140.27343, 35.67514]
]
};
// To draw a line across the 180th meridian,
// if the longitude of the second point minus
// the longitude of original (or previous) point is >= 180,
// subtract 360 from the longitude of the second point.
// If it is less than 180, add 360 to the second point.
if (doesCrossAntimeridian) {
const startLng = geometry.coordinates[0][0];
const endLng = geometry.coordinates[1][0];
if (endLng - startLng >= 180) {
geometry.coordinates[1][0] -= 360;
} else if (endLng - startLng < 180) {
geometry.coordinates[1][0] += 360;
}
}
return geometry;
}
});
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="robots" content="noindex">
<title>Display line that crosses 180th meridian</title>
<link rel="stylesheet" href="./style.css">
</head>
<body>
<div id="map"></div>
<script type="module" src="./main.js"></script>
</body>
</html>
body {margin: 0; padding: 0;}
#map {position: absolute; top: 0; bottom: 0; width: 100%;}
