[OpenLayers-Users] WMS, Google Map, and Vector Layer

[Chris Garstin]

Hi Arnd,

You suggestions have been extremely helpful, and I've been able to have the
vector layer and the WMS/Google layers properly overlayed.  I can't believe
it took me so long to figure it out, but there's a lot to learn.

I've noticed now that the Ontario Basic Mapping layer does not appear now. 
It loads data from the server, but it does not render any data into the map. 
Is this because that WMS may not support the projection I'm trying to
convert to?

Does this mean I might have to look into pro4js?

Thanks again for all your help Arnd, very much appreciated.

Regards
Chris




Arnd Wippermann wrote:
> 
> Hi Chris,
> 
> There are a couple of reasons for what you see or not see
> 
> 1. map creation without options will lead to projection EPSG:4326.
> 
> 2. Google maps can used with EPSG:4326, but data in EPSG:4326 will be
> shifted.
> 
> 3. transformation of coordinates in OpenLayers are only possible for
> EPSG:4326 and EPSG:900913 or by adding proj4js to your application for
> other
> projections, otherwise nothing happens.
>    Your features are drawn in the given coordinates on a map with
> projection
> EPSG:4326. Because EPSG:4326 and EPSG:4269 seems to be the same, your
> features are in the view but will be shifted on the Google layer.
> 
> Create your map in EPSG:900913.
> 
> var options = {
>     controls:[], //create map without controls -> add them later
>     projection: new OpenLayers.Projection("EPSG:900913"),
>     displayProjection: new OpenLayers.Projection("EPSG:4326"),
>     units: "m",
>     numZoomLevels: 18,
>     maxResolution: 156543.0339,
>     maxExtent: new OpenLayers.Bounds(-20037508, -20037508,
>                                      20037508, 20037508.34)
> };
> var map = new OpenLayers.Map('TrackViewMap', options);
> 
> Set Google layer to sphericalMercator:true
> 
> Test the map without the use of proj4js by replacing EPSG:4269 with
> EPSG:4326
> 
> Transform your points (from, to)
> new OpenLayers.Geometry.Point("-80.2112656","44.3428574").transform(new
> OpenLayers.Projection("EPSG:4326"),new
> OpenLayers.Projection("EPSG:900913"))
> 
> Add the layers
> 
> Add the controls
> map.addControl(new OpenLayers.Control.LayerSwitcher());
> map.addControl(new OpenLayers.Control.PanZoomBar());
> map.addControl(new OpenLayers.Control.MouseDefaults());
> 
> Set your center and zoom
> map.setCenter(new
> OpenLayers.LonLat("-80.2112656","44.3428574").transform(new
> OpenLayers.Projection("EPSG:4269"),new
> OpenLayers.Projection("EPSG:900913")),0);
> map.zoomTo(12);
> 
> And I hope, you will be pleased with the result.
> 
> 
> Some hints:
> 
> your wms are added as baselayers, because they will added by default as
> baselayers, when the param transparent is not set to true. isBaseLayer and
> buffer are options.
> 
> var WMSLayer = new OpenLayers.Layer.WMS(title, url, {params}, {options});
> 
> var WMSLayer = new OpenLayers.Layer.WMS( 'Toporama Canada',
> 	["http://wms.ess-ws.nrcan.gc.ca/wms/toporama_en?"], {
> 	
> layers:'hydrography,vegetation,road_network,feature_names,landforms',
> 	format:'image/png',
> 	transparent: true }, {isBaseLayer:true, buffer:0} );
> 
> 
> You need only transform the features instead of all the points.
> 
> var mlsFeature = new
> OpenLayers.Feature.Vector(multiLineString.transform(new
> OpenLayers.Projection("EPSG:4326"),new
> OpenLayers.Projection("EPSG:900913")),null);
> 
> Regards,
> Arnd 
> 
> -----Ursprüngliche Nachricht-----
> Von: users-bounces at openlayers.org [mailto:users-bounces at openlayers.org] Im
> Auftrag von Chris Garstin
> Gesendet: Samstag, 22. August 2009 15:45
> An: users at openlayers.org
> Betreff: [OpenLayers-Users] WMS, Google Map, and Vector Layer
> 
> 
> Hello there,
> 
> I know this has been discussed many times, so please bear with me, as I've
> been spending hours trying to see how to fix my unique problem.
> 
> I have two WMS layers, and a Google layer in my map.  I also have an
> overlay, which is just a multiLineString.  This overlay appears fine over
> the WMS layers, but is shifted on the Google layer.  I know this has to do
> with projections, but am really struggling with understanding how to fix
> it.
> 
> My attempts have included:
> 
> - Reprojecting the Google map.
> - Reprojecting the WMS maps.
> - Reprojecting the Vectory data on the fly.
> - Creating a second Vector layer where the points are transformed.
> 
> None of these I am able to get to work, so an extra set of eyes would be
> greatly apprecaited.
> 
> You can see my attempts at:
> 
> http://oo.chrisgarstin.com/maptrack.php?id=75
> 
> Regards
> Chris
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