[Mass-Market-GEO] OpenSearch Geo feedback

Andrew Turner ajturner at highearthorbit.com
Fri Nov 16 15:16:07 EST 2007


On 11/16/07, Carl Reed OGC Account <creed at opengeospatial.org> wrote:
>
>
> Just to follow up on Frank's comments, it would be really nice if the
> expression (at least at the information model level) of a
> geo-point/line/poly where the same across multiple specs/standards.

Good point, and exactly what I was trying to do with OpenSearch-Geo.
Specifically I was trying to create harmonization with GeoRSS-Simple
and GeoJSON. Both of which, I believe, are similar/same as GML for
point/line/poly?


> For
> example, GeoRSS GML point. We are now using the same expression for a point
> geometry in the OASIS geo-oasis GML profile, the IETF PIDF-LO geoshape
> application schema, and a IEEE 1451 standard. In all cases, the expression
> of a point geometry is consistent with ISO 19107 and GML 3.1.1.
>
> As to coordinate order for a poly, why not follow what is expressed in ISO
> 19107 and GML 3.x.x?? Again for consistency and harmonization across
> communities of use.
>
> Regards
>
> Carl
>
> ----- Original Message -----
> From: Frank.Steggink at bentley.com
> To: mass-market-geo at opengeospatial.org
> Sent: Friday, November 16, 2007 10:05 AM
> Subject: [Mass-Market-GEO] OpenSearch Geo feedback
>
>
>
> Hello list,
>
> I've just read the Geo extension of OpenSearch, and have a few suggestions.
>
> Lat and lon parameters: maybe it's just me, but I would prefer only one
> parameter for location. Now you'll need two parameters to describe one
> location. How about geo:point?
>
> Template:
> http://example.com/?q={searchTerms}&pw={startPage?}&center={geo:point?}&r={geo:radius?}&format=rss
> Example: http://example.com/?q=pizza&center=43.25,-123.45&format=rss
> This way you'll also avoid a potential problem that the second parameter
> should be present if the first one has been given. (Both are optional.)
>
> Polygon parameter: there is some discussion about the order of the vertexes.
> Andrew suggested clockwise order here. At the GeoRSS list there is a
> question about the suggested polygon order, and the ESRI Shapefile spec says
> that (the exterior of) a polygon should be also in clockwise order. I think
> it is pretty hard to enforce this. An example: if a client lets a user draw
> a polygon as the search area, the client should not forget to reorder the
> vertexes if the user has drawn it counter clockwise. Do you expect that all
> potential clients will do this?
>
> The reason for the vertex order is to determine what is inside or outside
> the polygon, especially near the international date line. If unambiguity is
> necessary, it can also be achieved by inserting multiple points when the
> longitude difference between two points will be really bigger than 180
> degrees. But also in this case it depends on the client if it will check
> this. What approach would be the easiest for most client?
>
> Maybe it is better to make an exception for the longitude range in this
> case, so that the longitudes can exceed 180 when the date line is crossed?
> This was allowed in WFS 1.1.1 for bounding boxes, but it's no longer
> mentioned in WFS 1.3.0, so I guess this suggestion is out of the question :)
>
> How is crossing the date line actually handled for the box parameter? If
> maxX < minX, does it mean that the box crosses the date line?
>
> Lastly, I'm wondering if there are already some clients and servers out
> there using this draft of the OpenSearch Geo extension.
>
> Regards,
>
> Frank Steggink
>
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-- 
Andrew Turner
ajturner at highearthorbit.com      42.2774N x 83.7611W
http://highearthorbit.com              Ann Arbor, Michigan, USA
Introduction to Neogeography - http://oreilly.com/catalog/neogeography


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