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Re: [udig-devel] Single UDig Layer with Multipe WMS Layers
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Joe Dente wrote:
Hi,
Is it possible to fetch multiple WMS layers merged into a single
IGeoResource?
Point of interest: uDig will send out a single GetMap request if several
WMS Layers from the same server are on your Map. So I find your
question a bit surprising.
Sort of; WMS Layers have a parent / child relationship. Many WMS servers
let you request a folder and will draw you a picture of all of the
contents. This is especially important when the folder contains the same
information at different scales; it allows you to automatically display
data at the correct resolution.
The second answer is yes; you can define a GeoResource on your own that
acts as a "view" combining several existing WMS layers. This is a
construct that would only be available on the client; it does not
reflect anything to do with the server, and it would be a fair bit of work.
Can I ask for clarification; you actually mean IGeoResource and not Layer?
I have UDig connected to a WMS server on Geotools. I construct my
layers by first adding the WMS server to the catalog and then using
ICatalog.getById() to retrieve layers from the WMS server. This works
well for adding IGeoResources to my map one at a time. I would like
to fetch multiple layers in a single request so that Geoserver can do
all of the work involved in merging multiple WMS images into a single
image. For example, with openMap I can use
http://localhost:8080/geoserver/wms?&request=GetMap&layers=tiger:poly_landmarks,tiger:tiger_roads
<http://localhost:8080/geoserver/wms?&request=GetMap&layers=tiger:poly_landmarks,tiger:tiger_roads>
to retrieve multiple layers with a single request, so that openMap
only receives a single image representing both layers; all of the
calculations involving features and combining the two layers into a
single image are performed by the non-client computer hosting
Geoserver. I would like to do something similar with UDig while
interacting with the catalog containing my WMS.
Right so if you have dragged poly_landmarks and tiger_roads onto a Map
in uDig you will find a single request is sent off to GeoServer as you
pan around.
Now it could be that as you drag them on one at a time; each request is
sent off on its own. We could ask the Renderer to not do anything when
performing a drag with a couple of things selected ....
After you start panning around a bit and you can check your geoserver to
confirm that a single GetMap request is sent with both layers listed.
Cheers,
Jody
