Making ISS 🛰️ tracker using Leaflet and Svelte

shriji profile image Shriji ・3 min read

This weekend I built ISS Tracker using leaflet a map provider without API or paywalls and there aren't many examples with Svelte implementation.

Leaflet has excellent documentation for JS most things can be achieved with just JS.



  1/ Svelte starter template (https://svelte.dev/)
  2/ ISS API (http://open-notify.org/Open-Notify-API/)
  3/ Leaflet via NPM (https://www.npmjs.com/package/leaflet)
  4/ *some amount of patience.*

Using the boilerplate fetch with svelte and obtaining the json data from the API.

const URL = "http://api.open-notify.org/iss-now.json"
async function fetchInfo() {
    const res = await fetch(URL).then(async data => {
    let d = await data.json();
    lat = d.iss_position.latitude
    lon = d.iss_position.longitude
    marker.setLatLng([lat, lon]).update();
    m.panTo([lat, lon]);

This gives us latitude and longitude that which we can plot on the map. The setTimeout() is to set positions of the ISS every 5 seconds 😉.

Now leaflet will test your patience basically it is a mash of several tutorials here https://leafletjs.com/examples.html 😅

Here is a small snippet that will help you thanks to this post
The base config can be done like this

    import * as L from 'leaflet';

//fancy custom icon
    var ISS_Icon = L.icon({
        iconUrl: './favicon.png',
        iconSize: [48, 48], // size of the icon

    function createMap(container) {
        m = L.map(container).setView([0, 0], 2);
        marker  = L.marker(m.getCenter(), {icon: greenIcon}).addTo(m)
            'https://{s}.basemaps.cartocdn.com/rastertiles/voyager/{z}/{x}/{y}{r}.png', {
                attribution: `&copy;<a href="https://www.openstreetmap.org/copyright" target="_blank">OpenStreetMap</a>`,
                subdomains: 'abcd',
                maxZoom: 14,
        return m;
    function mapAction(container) {
        map = createMap(container);
        return {
            destroy: () => {

Because leaflet can't repaint itself you will find some grey patches without it a combination of <svelte:window> calling the resizeMap() will fix it.

    function resizeMap() {
        if (map) {

<svelte:window on:resize={resizeMap} />

<div style="height:600px;width:100%" use:mapAction /> //invokes the map 

Now let's consume the other good juicy stuff from that API. ISS crosses above your location from here obtain and list next 5 passes from the obtained from Using the Geolocation API and the API has CORS... Hmm... 🤔🤔🤔 We can use https://cors-anywhere.herokuapp.com/ before the URL and get the data 😝

let warntext = 'Please allow location access to know when ISS will pass your location.'

    function getLocation() {
        if (navigator.geolocation) {
        } else {
            console.log("Geolocation is not supported by this browser / Not shared")

    function showPosition(position) {
        console.log(position.coords.latitude, position.coords.longitude);
        fetchPasses(position.coords.latitude, position.coords.longitude)
    let ISSPass = '';
    async function fetchPasses(lt, ln) {
        warntext = 'loading...'
        const res = await fetch(`https://cors-anywhere.herokuapp.com/${passes}lat=${lt}&lon=${ln}`).then(
    async data => {
            let d = await data.json();
            ISSPass = await d.response;
            warntext = 'Check below for the passes!'



And in the svelte we can populate like this

        {#each ISSPass as item} 
                {new Date(item.risetime*1000).toLocaleString()} <br>

Thanks for reading my post it's little longer than my usual posts.

Here is the repo.



Posted on by:

shriji profile



Co-Founder @anoram. High Performance JavaScript Apps. I created https://vadivelu.anoram.com/ and https://biriyani.anoram.com/ API.


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