[georss] GeoRSS polygon/line elevation

[Ron Lake]

Hi,

Relative to my example as Sean pointed out there is a dimension
attribute to indicate the number of coordinates.  Note that this is
really only a strong hint, since the number of coordinates should be
determined from the CRS.  A compound CRS (e.g. one providing elevation
separate from say latitude and longitude) might be referenced in your
example:

	<gml:Point srsName="... r234" (made up!)>
		<gml:pos>100 200 143</gml:pos>
	</gml:Point>

So I could determine the number of coordinates just by counting in this
case (only for Points of course) or by using the CRS (srsName attribute)
to get the number of coordinates (dimension).  This is always the
ultimate determinate of the dimension.  The data supplier can use the
dimension attribute and is responsible for ensuring that this agrees
with the CRS referenced in the geometry.

Note of course for some problems I might have only a 1D coordinate
system and thus only 1 coordinate (could be elevation or distance along
a road).

Cheers

Ron

-----Original Message-----
From: georss-bounces at lists.eogeo.org
[mailto:georss-bounces at lists.eogeo.org] On Behalf Of Sean Gillies
Sent: January 24, 2007 7:53 AM
To: georss at lists.eogeo.org
Subject: Re: [georss] GeoRSS polygon/line elevation

Andrew Turner wrote:
> There doesn't appear to be any mechanism in v1 of GeoRSS spec to
> handle elevation in anything but a Point.
> 
> <georss:point elev="313">45.256 -110.45</georss:point>
> 
> but
> <georss:polygon>
> 	45.256 -110.45 46.46 -109.48 43.84 -109.86 45.256 -110.45
> </georss:polygon>
> 
> would be?
> <georss:polygon elev="313 310 306 313">
> 
> nothing seems apparent in GML either - so I must just be missing it.
> 
> Andrew

Andrew, in GML:

<gml:LineString>
   <gml:posList dimension="3">0.0 0.0 1000.0 ...</gml:posList>
</gml:LineString>

The dimension attribute tells you the length of the coordinate tuples in

the posList.

Cheers,
Sean

-- 
Sean Gillies
http://zcologia.com/news

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