Openlayers Track example

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Screenshot of the result

Introduction

This example show you how to display one or multiple GPX Tracks in an OpenLayers map.

This example is based on the OpenLayers Simple Example.

Instructions

Requirements

  • Track as a .gpx file
  • Text editor (such as Notepad, or any other text editor)
  • Webbrowser (Firefox, Internet Explorer, ..)
  • Access to a Webserver (but see below for solutions)
  • 3 minutes of your time :-)

Steps

  • Place the gpx file(s) into a folder on the webserver
  • Create the following HTML file (also on the webserver):
<html>
<head>
	<!-- Source: http://wiki.openstreetmap.org/wiki/Openlayers_Track_example -->
	<title>Simple OSM GPX Track</title>
	<!-- bring in the OpenLayers javascript library
		 (here we bring it from the remote site, but you could
		 easily serve up this javascript yourself) -->
	<script src="http://www.openlayers.org/api/OpenLayers.js"></script>
	<!-- bring in the OpenStreetMap OpenLayers layers.
		 Using this hosted file will make sure we are kept up
		 to date with any necessary changes -->
	<script src="http://www.openstreetmap.org/openlayers/OpenStreetMap.js"></script>

	<script type="text/javascript">

		var map; //complex object of type OpenLayers.Map

		function init() {
			map = new OpenLayers.Map ("map", {
				controls:[
					new OpenLayers.Control.Navigation(),
					new OpenLayers.Control.PanZoomBar(),
					new OpenLayers.Control.LayerSwitcher(),
					new OpenLayers.Control.Attribution()],
				maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34),
				maxResolution: 156543.0399,
				numZoomLevels: 19,
				units: 'm',
				projection: new OpenLayers.Projection("EPSG:900913"),
				displayProjection: new OpenLayers.Projection("EPSG:4326")
			} );

			// Define the map layer
			// Here we use a predefined layer that will be kept up to date with URL changes
			layerMapnik = new OpenLayers.Layer.OSM.Mapnik("Mapnik");
			map.addLayer(layerMapnik);
			layerCycleMap = new OpenLayers.Layer.OSM.CycleMap("CycleMap");
			map.addLayer(layerCycleMap);
			layerMarkers = new OpenLayers.Layer.Markers("Markers");
			map.addLayer(layerMarkers);

			// Add the Layer with the GPX Track
			var lgpx = new OpenLayers.Layer.Vector("Lakeside cycle ride", {
				strategies: [new OpenLayers.Strategy.Fixed()],
				protocol: new OpenLayers.Protocol.HTTP({
					url: "around_lake.gpx",
					format: new OpenLayers.Format.GPX()
				}),
				style: {strokeColor: "green", strokeWidth: 5, strokeOpacity: 0.5},
				projection: new OpenLayers.Projection("EPSG:4326")
			});
			map.addLayer(lgpx);

			// Add a Layer with Marker
			var size = new OpenLayers.Size(21, 25);
			var offset = new OpenLayers.Pixel(-(size.w/2), -size.h);
			var icon = new OpenLayers.Icon('http://www.openstreetmap.org/openlayers/img/marker.png',size,offset);
			layerMarkers.addMarker(new OpenLayers.Marker(lonLat,icon));

			// Start position for the map (hardcoded here for simplicity,
			// but maybe you want to get this from the URL params)
			var lat=47.496792;
			var lon=7.571726;
			var zoom=13;
			var lonLat = new OpenLayers.LonLat(lon, lat).transform(new OpenLayers.Projection("EPSG:4326"), map.getProjectionObject());
			map.setCenter(lonLat, zoom);
		}
	</script>

</head>
<!-- body.onload is called once the page is loaded (call the 'init' function) -->
<body onload="init();">
	<!-- define a DIV into which the map will appear. Make it take up the whole window -->
	<div style="width:90%; height:90%" id="map"></div>
</body>
</html>
  • Open the html file in a browser

Customization

If the basic example works in your web browser, you can go on to adapt the web page to your needs.

  • Change the starting point and the map zoom
  • open the html file in the text editor and change the following lines:
// Start position for the map (hardcoded here for simplicity
// but maybe you want to get this from the URL params)
var lat=47.496792;
var lon=7.571726;
var zoom=13;
  • Change the track
  • open the html file in the text editor and change the following lines:
// Add the Layer with GPX Track
var lgpx = new OpenLayers.Layer.Vector("Lakeside cycle ride", {
	strategies: [new OpenLayers.Strategy.Fixed()],
	protocol: new OpenLayers.Protocol.HTTP({
		url: "around_lake.gpx",
		format: new OpenLayers.Format.GPX()
	}),
	style: {strokeColor: "green", strokeWidth: 5, strokeOpacity: 0.5},
	projection: new OpenLayers.Projection("EPSG:4326")
});
map.addLayer(lgpx);
    • Lakeside cycle ride is the name of the track, this is displayed in the Layer switcher.
    • around_lake.gpx is the path to your GPX file on the server. NB you cannot call for a file from another domain.
    • style: {strokeColor: "green", strokeWidth: 5, strokeOpacity: 0.5} these control how the track looks on the map. See the OpenLayers documentation for details of what can be configured here.
  • If you would like to display more than one track, just copy these 2 lines and change the values again.

Common issues

Depending on the security settings, some web browsers (notably Internet Explorer and Google Chrome) may refuse to process JavaScript and/or load GPX files from disk in file://-type URLs, that is when your HTML file is accessed directly from your hard drive without a web server.

This may be circumvented by using a tiny, local HTTP server to access the files.

The Python programming language has a builtin web server which can be started by changing to the directory with the HTML files and then using the command

$ python -m http.server 8000 # for Python 3
$ python -m SimpleHTTPServer 8000 # for Python 2

Then the files can be accessed by opening httpː//localhostː8000/ in your web browser.

There are also small web server implementations available for Microsoft Windows, for example tinyserver [1], which can be used as standalone applications, without needing python.