[OpenLayers-Users] Dynamic and tile map service

[Doug Kunzman]

I new to open layers and have looked at all of the examples and 
documentation I'm having trouble figuring something out.
We are loading some USGS base imagery as a tile map service (I think this 
is the correct term) using this call

 new OpenLayers.Layer.XYZ("USGS Base Imagery Map",

but when the layers are no longer available because the user has zoomed-in 
the layers don't display.  I've talked to a
ESRI ArcServer expert and he said "We need to switch based upon the zoom 
level from a tile map service to a dynamic map service."

Can someone give me some hints about displaying layers as a dynamic map 
service?

I'm doing this at the current time but it isn't working:

        rastermap1 = new OpenLayers.Layer.WMS("USGS Base Imagery Map", 
        "
http://raster1.nationalmap.gov/ArcGIS/rest/services/TNM_Small_Scale_Imagery/MapServer/export
", {
                 projection: "EPSG:900913", sphericalMercator: true, 
group: "basemap", meta:false
                });
                rastermap1.visibility = true;
                map.addLayer(rastermap1);

I noticed that this KML call seems to work.
http://raster1.nationalmap.gov/ArcGIS/rest/services/TNM_Small_Scale_Imagery/MapServer/kml/regions/0-1-1.kmz?
where you have near unlimited zoom capability in Google Earth.

this is the meta data for the layer I'm trying to display can be found at 
http://raster1.nationalmap.gov/ArcGIS/rest/services/TNM_Small_Scale_Imagery/MapServer



-- Doug
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