Re: Good practice for RDF publishing of multiple geometries with different CRSs?

Hi Frans,

I think we would need to separate the geometry from it's serialization 
and add some metadata:

ex:location1234
   a dcterms:Location;
   locn:geometry ex:geom1234 .
ex:geom1234
   my:hasSerialization [ my:usesSRS 
<http://www.opengis.net/def/crs/EPSG/0/28992>;
                                   geosparql:asWKT 
"<http://www.opengis.net/def/crs/EPSG/0/28992> POINT(139715 
476443)"^^geosparql:wktLiteral ];
   my:hasSerialization [ my:usesSRS 
<http://www.opengis.net/def/crs/OGC/1.3/CRS84>;
                                   geosparql:asWKT "POINT(5.1633 
52.2758)"^^geosparql:wktLiteral ] .


I suppose my:hasSerialization and my:usesSRS would need to be 
standardized to be useful.

An alternative would be to use a GeoSPARQL query with getSRID() as a filter.

SELECT ?geom
WHERE {
   ex:location1234 locn:geometry ?geom .
   FILTER (ogcf:getSRID(?geom) = 
<http://www.opengis.net/def/crs/EPSG/0/28992>)
}

Thanks,
Matt

On 4/7/2016 9:44 AM, Frans Knibbe wrote:
> Hello,
>
> In preparation of publishing a dataset as Linked Data I am faced with 
> a recurring problem: in which way can I publish a geometry with 
> multiple CRSs?
>
> This requirement is captured in the UCR document and will hopefully be 
> tackled by the BP document and would probably be solved if we develop 
> anagreed upon spatial ontology 
> <https://lists.w3.org/Archives/Public/public-sdw-wg/2016Mar/0057.html>, but 
> perhaps it is possible to think of a good solution now that will help 
> further progress?
>
> The problem is as follows: As a data publisher, I want to publish 
> geometric data in additional reference systems next to the source CRS, 
> as a convenience for consumers. So data could look like this (in 
> Turtle, using the Core Location Vocabulary and GeoSPARQL) :
>
> ex:location1234
>   a dcterms:Location;
> locn:geometry "<http://www.opengis.net/def/crs/EPSG/0/28992> 
> POINT(139715 476443)"^^geosparql:wktLiteral
>   , "POINT(5.1633 52.2758)"^^geosparql:wktLiteral .
>
> In this example, the source data use the Dutch national reference 
> system and the geometry is published with CRS84 too. A user (for 
> example a web developer that wants to be able to plot the data on a 
> map, or a researcher that want to combine the data with other spatial 
> data) will typically be interested in using only one CRS. How can a 
> data consumer get the geometry data in the preferred CRS? And what can 
> de data publisher do to accommodate that?
>
> Does someone have a good idea of how to do this?
>
> Regards,
> Frans
>
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