[OpenLayers-Users] How to restrict map extent?

[bartvde at osgis.nl]

Have a look at restrictedExtent on the Map object.

Best regards,
Bart

>
> Hello,
>
> I'm trying to set up my own map app using OSM data, mapnik + PostGIS to
> render map, mod_tile to serve tiles and OpenLayers for map display.
> Everything works fine, except I cannot restrict viewable map area in
> OpenLayers. I want user to see only area of one city, and not to zoom out
> outside it.
>
> So I have downloaded OSM XML file with map of requested area, loaded it to
> PostGIS with command like this:
> osm2pgsql -d some-db -p some-prefix -U some-user -H localhost
> /neuromap/trunk/data/wroclaw-map.osm -c -E 900913 -b
> 16.8188,50.9974,17.2235,51.2065
>
> (BTW: data is loaded to PostGIS but osm2pgsql says:
> StartElement: Unknown element name: bounds
> EndElement: Unknown element name: bounds - maybe this is a problem?)
>
> I create OpenLayers map as follows:
>
> var mapnikLayer = new OpenLayers.Layer.OSM("world", "http://some-url...");
> var mapOptions = {
>     controls:[
>         new OpenLayers.Control.PanZoomBar(),
>         new OpenLayers.Control.Permalink(),
>         new OpenLayers.Control.ScaleLine(),
>         new OpenLayers.Control.OverviewMap(),
>         new OpenLayers.Control.Permalink('permalink'),
>         new OpenLayers.Control.MousePosition(),
>         new OpenLayers.Control.KeyboardDefaults(),
>         new OpenLayers.Control.MouseDefaults()
>     ],
>     maxExtent: new OpenLayers.Bounds(1863611,6614478,1924760,6660340),
>     maxResolution: 0.6,
>     units: 'm',
>     //numZoomLevels: 19,
>     projection: new OpenLayers.Projection("EPSG:900913")
>   }
>
>   var map = new OpenLayers.Map ("wroc-map", mapOptions);
>   map.addLayer(mapnikLayer);
>   ...
>
> When I call map.zoomToMaxExtent(), OpenLayers shows what I expect to be
> whole world area - not my city. When I display map.getMaxExtent() i get:
>
> max extent: left-bottom=(-20037508.34,-20037508.34)
> right-top=(20037508.34,20037508.34)
>
> so maxExtent is evidently not set.
>
>
> I can do of course:
> map.zoomToExtent(new OpenLayers.Bounds(1863611,6614478,1924760,6660340))
> but that's not what I want because zoom level is set to 11. I would prefer
> to have zl=0 with the view of whole city.
>
>
> I also tried to use
> scales:[220000,150000,100000,50000,20000,10000,5000,2000,1000] instead of
> maxExtent and maxResolution, but though I call zoomToExtent... and
> viewport has this extent I can see only placeholder tile images with
> message "...more OSM data soon".
>
>
> Is restricting of viewable map area possible?
> What am I doing wrong?
> Please help.
>
> Shymon
>
>
> --
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> http://n2.nabble.com/How-to-restrict-map-extent--tp2568378p2568378.html
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>
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