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I am using OpenLayers 2 and Geoserver.
I have a few WFS layers and an OpenStreetMap as a Baselayer. I want to change the vector layers' visibility at certain zoom levels, by using min/maxScale or min/maxResolution, but it doesn't seem to work. In the following example I use only one of the layers as a test.

My code using min/maxScale:

<script defer="defer" type="text/javascript">           
    var map;

    // pink tile avoidance
    OpenLayers.IMAGE_RELOAD_ATTEMPTS = 5;
    // make OL compute scale according to WMS spec
    OpenLayers.DOTS_PER_INCH = 25.4 / 0.28;

    function init(){

        // Save-strategy
        var saveStrategy = new OpenLayers.Strategy.Save();

        // Controls
        var controls = [                
            new OpenLayers.Control.ArgParser(), 
            new OpenLayers.Control.Navigation(),
            new OpenLayers.Control.PanZoomBar({position: new OpenLayers.Pixel(2, 15)}),
            new OpenLayers.Control.LayerSwitcher(),
        ];              

        //Options
        var options = {
            scales: [500000, 100000, 50000, 25000, 10000, 5000],
            projection: "EPSG:4326",
            displayProjection: "EPSG:4326",
            units: 'm'
        }   

        //Map
        map = new OpenLayers.Map('map', /*{controls: controls}*/ options);  //Don't quite know how to use both: controls and options; 
                                                                            //options doesn't work anyway

        //Basemap
        var osm = new OpenLayers.Layer.OSM("Simple OSM Map");               
        map.addLayer(osm);

        //Layer
        var test = new OpenLayers.Layer.Vector("xName", {               
            strategies: [new OpenLayers.Strategy.Fixed(), saveStrategy],
            minScale: 1/50000,
            maxScale: 1/25000,
            protocol: new OpenLayers.Protocol.WFS({
            url: SETTINGS.BASE_URL,
            featurePrefix: 'xNS',
            featureNS: "xNS",
            //extractAttributes: true,
            featureType: "xName",
            }),
                styleMap: new OpenLayers.StyleMap({
                    "default": new OpenLayers.Style({
                        "pointRadius": 2,
                        fill: true,
                        fillColor: "#8d006a",
                        strokeColor: "#000000",
                        strokeWidth: 0.2
                    })
                })
            });
        //Add Layer

        map.addLayer(test); 

        //Set Map Center                
        map.setCenter(
            new OpenLayers.LonLat(27.1, 47.55).transform(
                new OpenLayers.Projection("EPSG:4326"),
                map.getProjectionObject()
            ), 9
        );          
    }
</script>  

If I use min/max Scale nothing happens, the layers are visible at all zoom levels. Also, in the browser Console I see that the units didn't change, even if I specified "meters" in my options, I still see that "degrees" are used.

I tried the solution listed here: "Layer visibility using maxscale minscale not working" - using min/maxResolution, but it still doesn't work.

"maxScale or minScale dont working in vector (from wfs) layer" doesn't work either.

My code using min/maxResolution:

        //Basemap
        var osm = new OpenLayers.Layer.OSM("Simple OSM Map");               
        map.addLayer(osm);

        //Layer
        var test = new OpenLayers.Layer.Vector("xName", {               
            strategies: [new OpenLayers.Strategy.Fixed(), saveStrategy],
            minResolution: 14.035643,
            maxResolution: 7.01782148,
            protocol: new OpenLayers.Protocol.WFS({
            url: SETTINGS.BASE_URL,
            featurePrefix: 'xNS',
            featureNS: "xNS",
            //extractAttributes: true,
            featureType: "xName",
            }),
                styleMap: new OpenLayers.StyleMap({
                    "default": new OpenLayers.Style({
                        "pointRadius": 2,
                        fill: true,
                        fillColor: "#8d006a",
                        strokeColor: "#000000",
                        strokeWidth: 0.2
                    })
                })
            });
        //Add Layer

        map.addLayer(test); 

When using min/maxResolution, the layers are no longer visible at any zoom level. They can be seen on the LayerSwitcher but cannot be selected. I suppose that at a certain resolution (the one specified) they should be visible and selectable, but that's not the case.

2

After several hours, I finally found the answer. It turns out that the scale on the map shows different values than the scale in the browser console (which I find odd), so I was adding the wrong values to the min/maxResolution.

Working code:

var test = new OpenLayers.Layer.Vector("xName", {               
                strategies: [new OpenLayers.Strategy.Fixed(), saveStrategy],
                minResolution: 0.001,
                maxResolution: 200,
                protocol: new OpenLayers.Protocol.WFS({
                url: SETTINGS.BASE_URL,
                featurePrefix: 'xNS',
                featureNS: "xNS",
                //extractAttributes: true,
                featureType: "xName",
                }),
  • How did you determine the min/max resolution for your vector, out of curiosity? – Sleep6 Jan 9 '17 at 20:26
  • Thanks. I did my maxResolution by trial and error (Binary Chop) – Matthew Lock Apr 3 '18 at 5:44

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