[Mass-Market-GEO] OpenSearch Geo feedback

Carl Reed OGC Account creed at opengeospatial.org
Fri Nov 16 15:50:26 EST 2007


Andrew -

Yes, you are correct for a point geometry at the info model level they are 
consistent. Your approach is also consistent with how location is expressed 
in iCalendar and iCard. However, life gets a bit more interesting when we 
begin looking at linestrings and polys :-)

Cheers

Carl

----- Original Message ----- 
From: "Andrew Turner" <ajturner at highearthorbit.com>
To: "Carl Reed OGC Account" <creed at opengeospatial.org>
Cc: <Frank.Steggink at bentley.com>; <mass-market-geo at opengeospatial.org>
Sent: Friday, November 16, 2007 1:16 PM
Subject: Re: [Mass-Market-GEO] OpenSearch Geo feedback


> 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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