[GIS] OpenLayers programmatically select base layer

openlayers-2

I have several base layers added to a map in an OpenLayers based application. There is only one that can be displayed at a time, as they are all base layers.

When the user changes the selected base layer, I store the name of the selected layer as a HTML5 local storage item (an improved cookie). When re-opening the application, I want to programmatically set the same base layer be displayed.

It works fine with layer.visibility = true if isBaseLayer is false, but not in the case when isBaseLayer is set to true.

Is there anything else I could try for this?

Best Answer

A combination of map.getLayersByName(name) and map.setBaseLayer(layer) should do this for you.

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[GIS] Using WFS Layer as a baselayer

I've just made a quick test http://ian01.geog.psu.edu/geoserver/www/wfs/wfs-baselayer.html and you can use a WFS as a baselayer. I suspect your problem is probably a Same-Origin problem - check with FireBug that the response to the request is there (if it works when you open it in a new tab but fails in the map then you need a proxy).

[GIS] OpenLayers weird problem with GoogleMaps base layer and WMS overlay

In OpenLayers, the base layer dictates what is going to be the "base spatial reference". So any overlay will be projected to the base srid. Since any base layer that comes from the consumer-based providers (google, bing, yahoo, etc) supports only 900913, then OpenLayers is doing the right thing for your.

If you do a GetCapabilities call on your server you will notice the following section:

<Layer queryable="1" opaque="0" noSubsets="0">
<Name>Catastro</Name>
<Title>Catastro</Title>
<Style>
<Name>Default</Name>
<Title>Default</Title>
<LegendURL width="160" height="500">
<Format>image/png</Format>
<OnlineResource xlink:type="simple" xlink:href="http://ovc.catastro.meh.es/Cartografia/WMS/simbolos.png"/>
</LegendURL>
</Style>
<BoundingBox SRS="EPSG:4230" minx="-18.409876" miny="26.275447" maxx="5.22598" maxy="44.85536"/>
<BoundingBox SRS="EPSG:4326" minx="-18.409876" miny="26.275447" maxx="5.22598" maxy="44.85536"/>
<BoundingBox SRS="EPSG:4258" minx="-18.409876" miny="26.275447" maxx="5.22598" maxy="44.85536"/>
<BoundingBox SRS="EPSG:32627" minx="770000" miny="3000000" maxx="2700000" maxy="5000000"/>
<BoundingBox SRS="EPSG:32628" minx="180000" miny="3000000" maxx="2170000" maxy="5000000"/>
<BoundingBox SRS="EPSG:23029" minx="-410000" miny="3000000" maxx="1650000" maxy="5000000"/>
<BoundingBox SRS="EPSG:23030" minx="-1050000" miny="3000000" maxx="1150000" maxy="5000000"/>
<BoundingBox SRS="EPSG:23031" minx="-1615000" miny="3000000" maxx="620000" maxy="5000000"/>
<BoundingBox SRS="EPSG:32629" minx="-410000" miny="3000000" maxx="1650000" maxy="5000000"/>
<BoundingBox SRS="EPSG:32630" minx="-1050000" miny="3000000" maxx="1150000" maxy="5000000"/>
<BoundingBox SRS="EPSG:32631" minx="-1615000" miny="3000000" maxx="620000" maxy="5000000"/>
<BoundingBox SRS="EPSG:25829" minx="-410000" miny="3000000" maxx="1650000" maxy="5000000"/>
<BoundingBox SRS="EPSG:25830" minx="-1050000" miny="3000000" maxx="1150000" maxy="5000000"/>
<BoundingBox SRS="EPSG:25831" minx="-1615000" miny="3000000" maxx="620000" maxy="5000000"/>
<BoundingBox SRS="EPSG:3785" minx="-2100000" miny="3000000" maxx="500000" maxy="5600000"/>
</Layer>

Lo and behold, 900913 is not an option. You may need to either:

modify the WMS server definition to make sure that 900913 is allowed as a valid reprojection
add a definition for that new srid (depends on what web server you are using)
a combination of thse

By looking at the URL, it seems you are using an ASP .NET WMS server, since Geoserver is java and Mapserver if cgi, and ArcGIS Server is .NET, I am going guess this is an ESRI server, so the instructions on how to modify this is here.

Update: As mkennedy points out, the official EPSG code for SphericalMercator (aka Google's projection) is 3857 and a previous assigned number was 3785. If you are wondering why there are so many numbers that refer to the same spatial reference, crschmidt's blog post will give you a clue...

Ian pointed out the relevant OpenLayer's documentation section to force OpenLayers to use that EPSG code instead.

Since your GetCapabilities section shows 3785, the code from the OL documentation won't work as is, you will need to replace all the 3857 for 3785.

Best Answer

Related Solutions

[GIS] Using WFS Layer as a baselayer

[GIS] OpenLayers weird problem with GoogleMaps base layer and WMS overlay

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