[georss] Intended lat/long order

[Ron Lake]

Hi,

 

The order is specified in the GML encoding for the CS (Note that the CRS
is made of many pieces of which the CS is one).  If you expand the CRS
in the UI you will see:



 

 

If you look at the GML for the CS (which is EPSG 6423) you will see:

 

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<EllipsoidalCS 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-cs-6423">

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<metaDataProperty>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<epsg:CommonMetaData>

  <epsg:type>ellipsoidal</epsg:type> 

  <epsg:informationSource>EPSG</epsg:informationSource> 

  <epsg:revisionDate>2004-01-05</epsg:revisionDate> 

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

  </epsg:CommonMetaData>

  </metaDataProperty>

  <identifier codeSpace="EPSG">urn:x-ogc:def:cs:EPSG:6423</identifier> 

  <name>Ellipsoidal 3D CS. Axes: latitude, longitude, ellipsoidal
height. Orientations: north, east, up. UoM: deg, deg, m.</name> 

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<axis>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<CoordinateSystemAxis gml:id="epsg-axis-108"
gml:uom="urn:x-ogc:def:uom:EPSG:9122">

  <descriptionReference xlink:href="urn:x-ogc:def:axis-name:EPSG:9901"
/> 

  <identifier codeSpace="EPSG">urn:x-ogc:def:axis:EPSG:108</identifier> 

  <axisAbbrev>Lat</axisAbbrev> 

  <axisDirection codeSpace="EPSG">north</axisDirection> 

  </CoordinateSystemAxis>

  </axis>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<axis>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<CoordinateSystemAxis gml:id="epsg-axis-109"
gml:uom="urn:x-ogc:def:uom:EPSG:9122">

  <descriptionReference xlink:href="urn:x-ogc:def:axis-name:EPSG:9902"
/> 

  <identifier codeSpace="EPSG">urn:x-ogc:def:axis:EPSG:109</identifier> 

  <axisAbbrev>Long</axisAbbrev> 

  <axisDirection codeSpace="EPSG">east</axisDirection> 

  </CoordinateSystemAxis>

  </axis>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<axis>

-
<http://www.epsg-registry.org/export.htm?gml=urn:x-ogc:def:cs:EPSG:6423>
<CoordinateSystemAxis gml:id="epsg-axis-110"
gml:uom="urn:x-ogc:def:uom:EPSG:9001">

  <descriptionReference xlink:href="urn:x-ogc:def:axis-name:EPSG:9903"
/> 

  <identifier codeSpace="EPSG">urn:x-ogc:def:axis:EPSG:110</identifier> 

  <axisAbbrev>h</axisAbbrev> 

  <axisDirection codeSpace="EPSG">up</axisDirection> 

  </CoordinateSystemAxis>

  </axis>

  </EllipsoidalCS>

 

This is the CS definition that is reflected in the UI.  You will see Lat
precedes Lon.  Note that many other CRS could use the same CS.


Sorry if I was not clear the first time.


R

 

 

 

----Original Message-----
From: Christopher Schmidt [mailto:crschmidt at metacarta.com] 
Sent: November 8, 2007 9:03 PM
To: Ron Lake
Cc: rico.hauke at daimler.com; georss at lists.eogeo.org
Subject: Re: [georss] Intended lat/long order

 

On Thu, Nov 08, 2007 at 08:43:15PM -0800, Ron Lake wrote:

> 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:

 

 

<Lots of XML>

 

How does this tell me that the order is lat, lon? Which tag did I need

to look at? I rea through it all, evne clicked the links ,but couldn't

undrstand where it said that.

 

Regards,

-- 

Christopher Schmidt

MetaCarta

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