[mapguide-users] How to deal with data served by ArcIMS with WMS

[Thomas M. Tuerke]

GetFeatureInfo is not so much ambiguous as it is loosely defined.  It’s purpose is to provide supplemental information on features at a certain location in the raster.  In short, it’s “hey server, what feature is that at pixel x,y of the map just asked for with these parameters?” (As such, it’s not a substitute for a WFS, which gives you raw, unrendered features as opposed to a pretty picture.)  It’s often used for roll-over effects such as “tool tips” or some other status display.

 

The ambiguity/loosely defined nature comes from what you can get back; the specification doesn’t limit the format to anything specific, leaving it up to the server to advertise the response formats it supports.  A server might offer plain text or HTML with some human-readable text, or some XML that might contain more detailed machine-readable feature information, or anything else… that’s left to the implementation to decide, and to the client to pick.  Not necessarily the height of interoperability, but workable solutions can be made from this.

 

Key to the understanding is that it usually follows a GetMap request, and is framed in terms of that previous request. In fact, most of the arguments of GetFeatureInfo are exactly the same as GetMap; that helps the server reconstruct the “image” (figuratively, if not literally) to determine what part of the map you’re requesting feature info for: the X,Y are, after all, expressed in pixel units, not geospatial coordinates.

 

And yes, MapGuide does support GetFeatureInfo, though it can be configured away wholesale in the templates, or on a layer-by-layer basis (that’s the purpose of the “queryable” attribute.)  The templates also allow you to define your own text-based response “format”, if you’re so inclined.  If memory serves, text/plain and text/html come for free out of the box.

 

- Thomas

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From: mapguide-users-bounces at lists.osgeo.org [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Jason Birch
Sent: Thursday, March 01, 2007 9:00 AM
To: MapGuide Users Mail List
Subject: RE: [mapguide-users] How to deal with data served by ArcIMS with WMS

 

 

WMS has a rather ambiguous interface called "GetFeatureInfo".  I don't believe that this is supported within MapGuide though, so anything you did with this would have to be custom code.

 

As Andy suggests, WFS would give you better access to the features, but I haven't done this myself either.

 

Jason

 

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From: mapguide-users-bounces at lists.osgeo.org [mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Ismael Cams
Sent: Thursday, March 01, 2007 06:48
To: mapguide-users at lists.osgeo.org
Subject: [mapguide-users] How to deal with data served by ArcIMS with WMS

Hello,

 

I am completely new to WMS and hope someone can give me some more information about following concern. 

In our case the WMS will be served by an ArcIMS. Will it be possible to use the data in the same way as it can be done with other resources (shp, sdf, ...). Is it for example possible to select a feature and get the properties of this feature ? Can the Webextensions API used as it was sdf/shp resource in the repository ? 

If not what are the limitations ?

 

Thanks in advance.

 

Kind regards,

Ismaël

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