CODEWITHSUNDEEP
latitude-longitudegml
umbersar
umbersar

Reputation: 1931

latitude/longitude info in a GML Bounding box

If, for example, we have bounding box as given below in gml:

<gml:Envelope> <gml:lowerCorner>42.943 -71.032</gml:lowerCorner> <gml:upperCorner>43.039 -69.856</gml:upperCorner> </gml:Envelope>

Now, for the lower corner, which value is the latitude and which is the longitude. Could not find this info in online documentation.

Thanks Wanderer

The above GML is formatted in GeoRSS

Upvotes: 2

Views: 2648

Answers (1)

Ian Turton
Ian Turton

Reputation: 10976

From the GML schema: 

<complexType name="EnvelopeType">
<choice>
<sequence>
<element name="lowerCorner" type="gml:DirectPositionType"/>
<element name="upperCorner" type="gml:DirectPositionType"/>
</sequence>
<element ref="gml:pos" minOccurs="2" maxOccurs="2">
<annotation>
<appinfo>deprecated</appinfo>
</annotation>
</element>
<element ref="gml:coordinates"/>
</choice>
<attributeGroup ref="gml:SRSReferenceGroup"/>
</complexType>
<element name="Envelope" type="gml:EnvelopeType" substitutionGroup="gml:AbstractObject">
<annotation>
<documentation>
Envelope defines an extent using a pair of positions defining opposite corners in arbitrary dimensions. The first direct position is the "lower corner" (a coordinate position consisting of all the minimal ordinates for each dimension for all points within the envelope), the second one the "upper corner" (a coordinate position consisting of all the maximal ordinates for each dimension for all points within the envelope). The use of the properties "coordinates" and "pos" has been deprecated. The explicitly named properties "lowerCorner" and "upperCorner" shall be used instead.
</documentation>
</annotation>
</element>

which leads to SRSReference group which contains the code to allow you to look up the axis order and units (amongst other things) about your coordinates.:

<attributeGroup name="SRSReferenceGroup">
<annotation>
<documentation>
The attribute group SRSReferenceGroup is an optional reference to the CRS used by this geometry, with optional additional information to simplify the processing of the coordinates when a more complete definition of the CRS is not needed. In general the attribute srsName points to a CRS instance of gml:AbstractCoordinateReferenceSystem. For well-known references it is not required that the CRS description exists at the location the URI points to. If no srsName attribute is given, the CRS shall be specified as part of the larger context this geometry element is part of.
</documentation>
</annotation>
<attribute name="srsName" type="anyURI"/>
<attribute name="srsDimension" type="positiveInteger"/>
<attributeGroup ref="gml:SRSInformationGroup"/>
</attributeGroup>

So without a specified SRS it is impossible to answer your question, we don't even know what units your coordinates are in.

Upvotes: 2

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