[georss] Simultaneous use of multiple SRS in a georss gml instance--clarification

[Pat Cappelaere]

Louis,

I do not understand your requirement of expressing that point using two CRS.
If you specify one CRS, the application should be able to reproject to the
user's desires, right?
What am I missing?
Thanks,
Pat.


> From: Louis Sweeny <louis.sweeny at ross-assoc.com>
> Date: Thu, 8 Mar 2007 13:48:04 -0800
> To: Raj Singh <raj at rajsingh.org>, <georss at lists.eogeo.org>
> Conversation: [georss] Simultaneous use of multiple SRS in a georss gml
> instance--clarification
> Subject: Re: [georss] Simultaneous use of multiple SRS in a georss gml
> instance--clarification
> 
> That makes sense.
> 
> I think this thread may be veering away from GeoRSS let me know if it
> should go elsewhere:
> 
> Here are the options I was considering:
> 
> A) Use whole geoRSS including "entry" ---> no need since we are not
> building feeds
> B)Use just the "where" and its children ----> are there likely to be
> "where" aware applications? That would not be RSS readers?
> C) Use just the georss elements "point" "line" ect ---> this would be
> purest, but also most distant from GeoRSS world
> 
> Thanks to other comments/research I think I understand now also, that I
> was probably asking the wrong question before: I'm trying to express the
> following business fact:
> 
> here is one point AS represented in two different CRSs (e.g. after a
> --If you are an application just "draw" it once (you pick which CRS to
> use). 
> 
> My solution of doing two "where", or two "point" elements, FOR THE SAME
> CONCEPTUAL LOCATION, but different CRCs will be confusing because there
> is no way (I can see in GML) of expressing this fact. This scenario
> arises, per my original post, when a CRS of record is re-projected to a
> new CRS, but the provider wishes to retain both.
> 
> One approach would be something like:
> <location>
>   <gml:Point>
>             <gml:pos>45.256 -71.92</gml:pos>
>          </gml:Point>
>   <alternative CRS>
> <gml:pos srsName="urn:ogc:def:crs:EPSG:6.6:26986">
> <gml:pos> -45.256 -110.45 </gml:pos>
> </gml:Point>
>        </location>
> 
> 
> Louis.
> 
> 
> 
> -----Original Message-----
> From: Raj Singh [mailto:raj at rajsingh.org]
> Sent: Thursday, March 08, 2007 11:40 AM
> To: Louis Sweeny; georss at lists.eogeo.org
> Subject: Re: [georss] Simultaneous use of multiple SRS in a georss gml
> instance
> 
> I would argue if you're not creating an RSS feed, you don't need the
> parent <georss:where> element. No need to conform exactly to the rules
> of GeoRSS in general, if no generic GeoRSS client will be parsing your
> particular brand of XML. Just use GeoRSS GML, include that schema in
> your existing .xsd and do the usual schema rules for saying you can have
> 2 GeoRSS GML elements.
> ---
> Raj
> 
> 
> On Mar 7, 2007, at 10:58 AM, Louis Sweeny wrote:
> 
>> Thanks for the reply.
>> 
>> While creating RSS "feeds" is definitely something we're interested in
> 
>> eventually, we are primarily looking to re-use the element definitions
> 
>> from GeoRss gml (from gml) in our schema, straight GML was too
>> complex.
>> For example we would use the where construct to provide the location
>> of an environmental monitoring point, as part of a larger schema. We
>> have a "proprietary" set of web services used to move/query instance
>> documents, and so are not using the "rss" part of georss gml  (e.g.
>> the "entry"
>> construct" quite yet, but we obviously want to build in forward
>> compatibility with it, so I'm not inclined to dink with the where
>> construct itself either.
>> 
>> So I'm probably stuck with two "where" constructs per entity, with a
>> relationshiptag but I agree that is awkward---for the reasons you
>> state.
>> 
>> 
>> 
>> -----Original Message-----
>> From: ajturner at gmail.com [mailto:ajturner at gmail.com] On Behalf Of
>> Andrew Turner
>> Sent: Tuesday, March 06, 2007 7:50 AM
>> To: Louis Sweeny
>> Cc: georss at lists.eogeo.org
>> Subject: Re: [georss] Simultaneous use of multiple SRS in a georss gml
> 
>> instance
>> 
>> Louis Sweeny <louis.sweeny at ross-assoc.com> wrote:
>>> 
>>> I'm a georss newbie.
>> 
>> Hi Louis, welcome to GeoRSS!
>> 
>>> 
>>> I don't see any way of doing this without having two "where"
>>> elements,
>> 
>>> for each feature, which seems awkward.
>> 
>> As was just evidenced by quite a long discussion - multiple
>> georss:where elements isn't supported as part of the standard (though
>> perhaps whomever is keeping score will give a +1 to the request tally)
>> 
>> Right now there isn't a way to specify this in GeoRSS. What would be a
> 
>> valid (and probably good) solution would be to provide two GeoRSS
>> feeds, the default being WGS-84 and then others for the appropriate
>> CRS. This could even just be a parameter to the URL (e.g.
>> ?crs=EPSG3089 or whatever)
>> 
>> I could see this as being useful for multiple where elements that had
>> their relationshiptag somehow specifying that it is just another
>> representation of the same point, but this may also be confusing to
>> readers or consumers. Splitting into a separate feed would make it
>> clear "the data in this feed is in *this* CRS"
>> 
>> Andrew
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> 
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