<figure><artwork><![CDATA[
p = crsp / uncertaintyp / parameter
uncertaintyp = ";uncertainty=" pnum
num = [ "-" ] pnum
pnum = 1*DIGIT [ "." 1*DIGIT ]
]]></artwork></figure>
<!-- BTW, this is needed for extensibility: crsp = "wgs84" / 1*( alphanum / "-" ) -->
<!-- New section above 4.4.3 -->
<section title="Location Uncertainty">
<t>The 'uncertainty' parameter indicates the amount of uncertainty in the location as a value in meters. Where a geo URI is used to identify the location of a particular subject, uncertainty indicates the uncertainty with which the location of the subject is known.
</t>
<t>The 'uncertainty' parameter is optional and it can appear only once. If no uncertainty is specified, this indicates that uncertainty is unknown or unspecified. If the intent is to indicate a specific point in space, uncertainty MAY be set to zero. Zero uncertainty and absent uncertainty are never the same thing.
</t>
</section>
<!-- BTW, you need to s/EPSG:6.6:/EPSG::/g - the "6.6" is not used in PIDF-LO [RFC5491] -->
<!-- Comment on Section 7
There is a great deal of duplication here - the mappings are effectively duplicated throughout. The from geo to GML are exactly the same as the from GML to geo sections with the order inverted. I don't think this adds value. -->
<!-- Second comment on Section 7
It's worth noting in general that GML uses the 'double' type from XML schema and that these examples assume that numbers in the form 3.59233e2 in GML are properly converted to decimal when placed in the 'geo' URI.
-->
<!-- Section 7 -->
<section title="2D GML 'Point'">
<t>A 2D GML <xref target="RFC5491">'Point'</xref> is constructed from a 'geo' URI that has two coordinates and an uncertainty parameter that is absent or zero. A GML point is always converted to a 'geo' URI that has no uncertainty parameter.
</t>
<figure><preamble>'geo' URI:</preamble>
<artwork><![CDATA[
geo:%lat%,%lon%
]]></artwork></figure>
<figure><preamble>GML document:</preamble>
<artwork><![CDATA[
<Point srsName="urn:ogc:def:crs:EPSG::4326"
xmlns="http://www.opengis.net/gml">
<pos>%lat% %lon%</pos>
</Point>
]]></artwork></figure>
<t>Note that a 'geo' URI with an uncertainty value of zero is converted to a GML 'Point', but a GML 'Point' cannot be translated to a 'geo' URI with zero uncertainty.
</t>
</section>
<section title="3D GML 'Point'">
<t>A 3D GML <xref target="RFC5491">'Point'</xref> is constructed from a 'geo' URI that has three coordinates and an uncertainty parameter that is absent or zero. A GML point is always converted to a 'geo' URI that has no uncertainty parameter.
</t>
<figure><preamble>'geo' URI:</preamble>
<artwork><![CDATA[
geo:%lat%,%lon%,%alt%
]]></artwork></figure>
<figure><preamble>GML document:</preamble>
<artwork><![CDATA[
<Point srsName="urn:ogc:def:crs:EPSG::4979"
xmlns="http://www.opengis.net/gml">
<pos>%lat% %lon% %alt%</pos>
</Point>
]]></artwork></figure>
</section>
<section title="GML 'Circle'">
<t>A GML <xref target="RFC5491">'Circle'</xref> is constructed from a 'geo' URI that has two coordinates and an uncertainty parameter that is present and non-zero.
</t>
<figure><preamble>'geo' URI:</preamble>
<artwork><![CDATA[
geo:%lat%,%lon%;uncertainty=%unc%
]]></artwork></figure>
<figure><preamble>GML document:</preamble>
<artwork><![CDATA[
<gs:Circle srsName="urn:ogc:def:crs:EPSG::4326"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0">
<gml:pos>%lat% %lon%</gml:pos>
<gs:radius uom="urn:ogc:def:uom:EPSG::9001">
%unc%
</gs:radius>
</gs:Circle>
]]></artwork></figure>
</section>
<section title="GML 'Sphere'">
<t>A GML <xref target="RFC5491">'sphere'</xref> is constructed from a 'geo' URI that has three coordinates and an uncertainty parameter that is present and non-zero.
</t>
<figure><preamble>'geo' URI:</preamble>
<artwork><![CDATA[
geo:%lat%,%lon%,%alt%;uncertainty=%unc%
]]></artwork></figure>
<figure><preamble>GML document:</preamble>
<artwork><![CDATA[
<gs:Sphere srsName="urn:ogc:def:crs:EPSG::4979"
xmlns:gml="http://www.opengis.net/gml"
xmlns:gs="http://www.opengis.net/pidflo/1.0">
<gml:pos>%lat% %lon% %alt%</gml:pos>
<gs:radius uom="urn:ogc:def:uom:EPSG::9001">
%unc%
</gs:radius>
</gs:Sphere>
]]></artwork></figure>
</section>
<-- I think that's it. I'm in two mins on the need for including anything special in comparison. On the one hand, I don't like the idea that each parameter gets special treatment. And special treatment is not possible for any extensions made to the format, making this a form of favouritism. On the other hand, numerical comparison makes sense for this parameter... -->
--Martin
> -----Original Message-----
> From: Alexander Mayrhofer [mailto:alexander.mayrhofer@nic.at]
> Sent: Thursday, 30 July 2009 11:19 AM
> To: Thomson, Martin; Richard Barnes; trac@localhost.amsl.com
> Cc: geopriv@ietf.org
> Subject: RE: [Geopriv] [geopriv] #14: uncertainty specification
>
>
> Richard, Martin,
>
> Are you willing to provide text for the "uncertainty" parameter?
>
> ;-)
>
> Alex
>
>
> > -----Original Message-----
> > From: geopriv-bounces@ietf.org
> > [mailto:geopriv-bounces@ietf.org] On Behalf Of Thomson, Martin
> > Sent: Thursday, July 30, 2009 11:10 AM
> > To: Richard Barnes; trac@localhost.amsl.com
> > Cc: geopriv@ietf.org
> > Subject: Re: [Geopriv] [geopriv] #14: uncertainty specification
> >
> > I would like to see this included, but suggest that the
> > uncertainty is best left as a parameter. It fits better
> > there. I don't know what you mean by "basic element", but if
> > it's part of the core list of numbers, then that would risk
> > the data from being mistaken for coordinate data (e.g. the
> > 4th dimension).
> >
> > > -----Original Message-----
> > > From: geopriv-bounces@ietf.org [mailto:geopriv-bounces@ietf.org] On
> > > Behalf Of Richard Barnes
> > > Sent: Wednesday, 29 July 2009 3:56 PM
> > > To: trac@localhost.amsl.com
> > > Cc: geopriv@ietf.org
> > > Subject: Re: [Geopriv] [geopriv] #14: uncertainty specification
> > >
> > > > Q) shall the draft specify such uncertainty, or shall it
> > leave that
> > > to an
> > > > external specification?
> > >
> > > The draft should specify an uncertainty radius in meters,
> > either as a
> > > basic element or as a parameter.
> > > _______________________________________________
> > > Geopriv mailing list
> > > Geopriv@ietf.org
> > > https://www.ietf.org/mailman/listinfo/geopriv
> >
> > --------------------------------------------------------------
> > ----------------------------------
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> > contain privileged, proprietary, or otherwise private information.
> > If you have received it in error, please notify the sender
> > immediately and delete the original. Any unauthorized use of
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> > [mf2]
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> > Geopriv@ietf.org
> > https://www.ietf.org/mailman/listinfo/geopriv
> >
> >
> >
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