Dynamically updating KML layer in OpenLayers

Question

How do I outsource a dynamic KML file using JavaScript in OpenLayers 2.10?

I want to refresh every 7 seconds.

Below are snippet of the given codes:

<script type='text/javascript'>

var map;

OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;

function init() {
    map = new OpenLayers.Map({
        allOverlays: true,
        controls: [
            new OpenLayers.Control.Navigation(),
            new OpenLayers.Control.PanZoom(),
        ]
    });
            
    var osm_layer = new OpenLayers.Layer.OSM();
    map.addLayer(osm_layer);
            
    var MyKML = "http://www.xyz.com/tld/mypath/myfile.kml"
    
    map.addLayer(new OpenLayers.Layer.GML("KML", MyKML, 
           {
            format: OpenLayers.Format.KML, 
            formatOptions: {
              extractStyles: true, 
              extractAttributes: true,
              maxDepth: 1
            }
           }));
    
    // Adding controls to map  
    map.addControl(new OpenLayers.Control.ScaleLine());
    map.render('map_element');
            
    map.setCenter(
            new OpenLayers.LonLat(101.587008,3.021612).transform(
                new OpenLayers.Projection("EPSG:4326"),
                map.getProjectionObject()
            ), 17
        );      
}
</script>

The KML file could refresh automatically in Google Earth but not in OpenLayers. That is the real problem.

And one huge complication is that I cannot visualize the KML layer in OpenLayers. Either I use static or passive KML file is quite successful.

Vadim · Accepted Answer · 2011-07-26 15:13:21Z

3

You need to add a Refresh Strategy to your layer. There's also discussion about this on the osgeo forum.

answered Jul 26, 2011 at 15:13

Vadim

3,9712 gold badges31 silver badges42 bronze badges

Add a comment |

Ian Turton · Accepted Answer · 2011-07-26 10:42:44Z

You'll need a Javascript timer, I use the following to refresh WMS layers but it should work for KML layers too. The code below redraws all the visible overlay layers but you could replace loop with a single layer in a variable.

var timerId = 0;

var refresher = function(button,event){
  for(layer in mappanel.map.layers){
    l = mappanel.map.layers[layer];
    if(l.isBaseLayer===false && l.getVisibility()){
        l.redraw(true);
    }
  }
};

var setTimer= function(interval){
  if(interval <= 0){
     interval = 30;
  }
  refresher();
  timerId = setInterval("refresher()",interval*1000);
};

var clearTimer=function(){
  clearInterval(timerId);
}

PolyGeo · Accepted Answer · 2024-02-08 03:01:40Z

I found the solution.

var map;

OpenLayers.IMAGE_RELOAD_ATTEMPTS = 3;

function init() {
    map = new OpenLayers.Map({
        allOverlays: true,
        controls: [
            new OpenLayers.Control.Navigation(),
            new OpenLayers.Control.PanZoom(),
        ]
    });
    var osm_layer = new OpenLayers.Layer.OSM();
    map.addLayer(osm_layer);
    map.addControl(new OpenLayers.Control.ScaleLine());
    map.render('map_element');
    map.zoomTo(5);  
        
    var osm = new OpenLayers.Layer.OSM();
    var vlayer = new OpenLayers.Layer.Vector( "Editable" );
    
    var MyKML = new OpenLayers.Layer.GML("KML", "myfile.kml",
            {
            projection: new OpenLayers.Projection("EPSG:4326"),
            //displayProjection: new OpenLayers.Projection("EPSG:900913"), 

            format: OpenLayers.Format.KML, 
            formatOptions: {
              extractStyles: true, 
              extractAttributes: true,
              maxDepth: 1
            }
           });
           
    map.addLayers([osm, vlayer, MyKML]);
    
    map.addControl(new OpenLayers.Control.PanZoomBar());
    map.setCenter(new OpenLayers.LonLat(101.587411,3.021547).transform(new OpenLayers.Projection ("EPSG:4326"),
    map.getProjectionObject()
    ), 
    15);

    window.setInterval(raingaugeRefreshData, 2000, MyKML);
}

function raingaugeRefreshData(layer){
            //setting loaded to false unloads the layer//
            layer.loaded = true;
            //setting visibility to true forces a reload of the layer//
            layer.setVisibility(true);
            //the refresh will force it to get the new KML data//
            layer.setUrl('mydomain.tld/mypath/myfile.kml?_salt='+Math.random());        
}

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