[OpenLayers-Users] How to understand and use zoom levels?

[Zhanna Maher]

Hello,

I must be missing something simple.  My function is as follows:

function init(lon,lat,zoom){
	 
	  	var map = new OpenLayers.Map('inter_map', { controls: [] });

		map.addControl(new
OpenLayers.Control.LayerSwitcher({activeColor:'green'}));
		  map.addControl(new OpenLayers.Control.PanZoomBar()); 
		  map.addControl(new OpenLayers.Control.MouseDefaults()); 
				
		  var layer_drg = new OpenLayers.Layer.WMS( "USGS Topo", 
                    "http://terraservice.net/ogcmap.ashx", {layers: 'drg'},
{numZoomLevels: 5}, {'buffer':1});			
						
		  var layer_doq = new OpenLayers.Layer.WMS( "USGS Aerial", 
                    "http://terraservice.net/ogcmap.ashx", {layers: 'doq' },
{'buffer':1} );		
	

		  var yahoo = new OpenLayers.Layer.Yahoo( "Yahoo" );

	 
	    map.addLayers([layer_drg,layer_doq,yahoo]);
		
	    map.setCenter(new OpenLayers.LonLat(lon, lat), zoom);
									
	var markersLayer = new OpenLayers.Layer.Markers("Survey mark" );
      var marker = new OpenLayers.Marker(
        new OpenLayers.LonLat(lon,lat), 
          new OpenLayers.Icon(
           "graphics/benchmark_icon.gif", 
           new OpenLayers.Size(11,11)
          ));
      markersLayer.addMarker(marker);
      map.addLayer(markersLayer); 	
			
		}

I'm trying to restrict the zoom levels on the DRG layer to 5; I want to only
be able to view levels 11-15.  I would like the map to load at zoom level
15.  But no matter what options I use (numZoomLevels, maxZoomLevel, etc.) I
cannot get the proper behavior.  I am assuming this is considered a 3rd
party later like Google and as such has pre-set resolutions, but maybe this
isn't the case.  Does anyone have an idea?  I can provide a live example if
necessary.

Thanks,
Zhanna

-----Original Message-----
From: Eric Lemoine [mailto:eric.c2c at gmail.com] 
Sent: Wednesday, December 19, 2007 2:37 PM
To: Zhanna Maher
Cc: users at openlayers.org
Subject: Re: [OpenLayers-Users] How to understand and use zoom levels?

[...]

This wiki page explains how to use scales/resolutions/etc. in OpenLayers.
<http://trac.openlayers.org/wiki/SettingZoomLevels>.

You can also check this example:
<http://www.openlayers.org/dev/examples/zoomLevels.html>.

[...]

--
Eric