[georss] Intended lat/long order

[Ron Lake]

Hi,

 

In GML (and this part of geoRSS is GML), the interpretation of
coordinates is determined by the CRS (Coordinate Reference System)
referenced by the sRSName attribute.  In geoRSS GML only one CRS is
currently supported and hence the attribute is assumed.  In effect:

 

<gml:Point>
       <gml:pos>37.4 -122.1</gml:pos>
</gml:Point>

 

Means

 

<gml:Point srsName = "urn:x-ogc:def:crs:EPSG:4326">
       <gml:pos>37.4 -122.1</gml:pos>
</gml:Point>

 

If you look up this URN at http://www.epsg-registry.org you will find:

 

 

 

Or the full definition in GML:

 

At 
http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
which is:

 

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <GeodeticCRS xmlns:gmd="http://www.isotc211.org/2005/gmd"
xmlns:gco="http://www.isotc211.org/2005/gco"
xmlns:epsg="urn:x-ogp:spec:schema-xsd:EPSG:0.1:dataset"
xmlns:gml="http://www.opengis.net/gml"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:rim="urn:oasis:names:tc:ebxml-regrep:xsd:rim:3.0"
xmlns="http://www.opengis.net/gml" gml:id="epsg-crs-4326">

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <metaDataProperty>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <epsg:CommonMetaData>

  <epsg:type>geographic 2D</epsg:type> 

  <epsg:informationSource>EPSG. See 3D CRS for original information
source.</epsg:informationSource> 

  <epsg:revisionDate>2007-08-27</epsg:revisionDate> 

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <epsg:changes>

  <epsg:changeID xlink:href="urn:x-ogc:def:change-request:EPSG:2002.151"
/> 

  <epsg:changeID xlink:href="urn:x-ogc:def:change-request:EPSG:2003.370"
/> 

  <epsg:changeID xlink:href="urn:x-ogc:def:change-request:EPSG:2006.810"
/> 

  <epsg:changeID xlink:href="urn:x-ogc:def:change-request:EPSG:2007.079"
/> 

  </epsg:changes>

  <epsg:show>true</epsg:show> 

  <epsg:isDeprecated>false</epsg:isDeprecated> 

  </epsg:CommonMetaData>

  </metaDataProperty>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <metaDataProperty>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:crs:EPSG:4326
>  <epsg:CRSMetaData>

  <epsg:projectionConversion
xlink:href="urn:x-ogc:def:coordinateOperation:EPSG:15593" /> 

  <epsg:sourceGeographicCRS xlink:href="urn:x-ogc:def:crs:EPSG:4979" /> 

  </epsg:CRSMetaData>

  </metaDataProperty>

  <identifier codeSpace="EPSG">urn:x-ogc:def:crs:EPSG:4326</identifier> 

  <name>WGS 84</name> 

  <domainOfValidity xlink:href="urn:x-ogc:def:area:EPSG:1262" /> 

  <scope>Horizontal component of 3D system. Used by the GPS satellite
navigation system and for NATO military geodetic surveying.</scope> 

  <ellipsoidalCS xlink:href="urn:x-ogc:def:cs:EPSG:6422" /> 

  <geodeticDatum xlink:href="urn:x-ogc:def:datum:EPSG:6326" /> 

  </GeodeticCRS>

 

So the order is (lat,lon) as Chris has already pointed out.

 

Cheers

Ron

 

 

From: georss-bounces at lists.eogeo.org
[mailto:georss-bounces at lists.eogeo.org] On Behalf Of
rico.hauke at daimler.com
Sent: November 8, 2007 5:52 PM
To: georss at lists.eogeo.org
Subject: [georss] Intended lat/long order

 


Hi list, 

This might sound stupid, but I was wondering what the lat/long order
(eg. in a point geometry) is intended to be? 

So if I am located at latitude 37.4 and longitude -122.1 which of the
following points are valid GeoRSS representations? 

1. lat/long order: 
<gml:Point>
       <gml:pos>37.4 -122.1</gml:pos>
</gml:Point> 

2. long/lat order: 
<gml:Point>
       <gml:pos>-122.1 37.4</gml:pos>
</gml:Point> 

The reason I am asking is that I have to pass the position string into a
WKT StringReader which wants the input to be in x/y (=long/lat) format. 

Thanks, 
Rico 

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