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

[Carl Reed OGC Account]

Wish you had been part of the Common Alert Protocol discussions when OASIS 
was deliberating how to handle CRS in the CAP standard. I kept asking for 
the "official" CRS to also be stated along with the default WGS 84 2d. Turns 
out that numerous countries have legal mandates for a CRS that is not WGS 
84!

Cheers

Carl

----- Original Message ----- 
From: "Louis Sweeny" <louis.sweeny at ross-assoc.com>
To: "Pat Cappelaere" <pat at cappelaere.com>; "Raj Singh" <raj at rajsingh.org>; 
<georss at lists.eogeo.org>
Sent: Thursday, March 08, 2007 9:22 PM
Subject: Re: [georss] Simultaneous use of multiple SRS in a georss 
gmlinstance--clarification


> This is as much about policy as it is technology.  If an agency uses
> state plane as its official CRS, but wishes to participate in a network
> of web services provided in lat/long, it can re-project on the fly of
> course, but it may want to have its "official" CRS carried along, as a
> form of full-disclosure/disclaimer---so that if there is any question
> about the "official" position, it is clear (e.g. if there is some error
> in the re-projection).
>
> Thanks for the feedback, I'm going to run what I've learned by the
> business users, and I'll report back to the list.
>
>
> -----Original Message-----
> From: Pat Cappelaere [mailto:pat at cappelaere.com]
> Sent: Thursday, March 08, 2007 7:09 PM
> To: Louis Sweeny; Raj Singh; georss at lists.eogeo.org
> Subject: Re: [georss] Simultaneous use of multiple SRS in a georss gml
> instance--clarification
>
> 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
>>> _______________________________________________
>>> georss mailing list
>>> georss at lists.eogeo.org
>>> http://lists.eogeo.org/mailman/listinfo/georss
>>
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