[GeoSciML] RE : srsName, srsDimension, and GML shapes [SEC=UNCLASSIFIED]
Eric.Boisvert at RNCan-NRCan.gc.ca
Mon Oct 22 20:10:50 EDT 2012
interesting: 07-036 (GML 3.2) Clause 9.10, p. 54
For convenience in constructing feature and feature collection instances, the value of the srsName attribute on the gml:Envelope which is the value of the gml:boundedBy property of the feature shall be inherited by all directly expressed geometries in all properties of the feature or members of the collection, unless overruled by the presence of a local srsName. Thus it is not necessary for a geometry to carry a srsName attribute, if it uses the same coordinate reference system as given on the gml:boundedBy property of its parent feature. Inheritance of the coordinate reference system continues to any depth of nesting, but if overruled by a local srsName declaration, then the new coordinate reference system is inherited by all its children in turn.
Notwithstanding this rule, all the geometries used in a feature or feature collection may carry srsName attributes, in order to indicate the reference system used locally, even if they are the same as the parent.
if I read correctly, srsName are inherited from parent elements, you just need to define a new one when you local srsName is different from the parent (essentially, overriding it)
De : geosciml-bounces+eric.boisvert=rncan-nrcan.gc.ca at lists.opengeospatial.org [geosciml-bounces+eric.boisvert=rncan-nrcan.gc.ca at lists.opengeospatial.org] de la part de Oliver.Raymond at ga.gov.au [Oliver.Raymond at ga.gov.au]
Date d'envoi : 22 octobre 2012 19:33
À : geosciml at lists.opengeospatial.org
Objet : [GeoSciML] srsName, srsDimension, and GML shapes [SEC=UNCLASSIFIED]
<gml:CompositeCurve gml:id="DDH123.curve" srsDimension="3" srsName="http://www.opengis.net/def/crs/EPSG/0/4939">
<gml:description>The 'real-world' shape of the drill hole. This is calculated from the borehole survey data.</gml:description>
<gml:LineString gml:id="DDH123.curve.segment.1" srsDimension="3" srsName="http://www.opengis.net/def/crs/EPSG/0/4939">
<gml:posList srsDimension="3" srsName="http://www.opengis.net/def/crs/EPSG/0/4939">
-25.0 119.0 210
-25.0 119.01 177
There are 3 places that you can encode srsName and srsDimension for a curved borehole shape - in gml:CompositeCurve, gml:LineString, and gml:posList. Currently the GeoSciML v3.0 schematron enforces srsDimension and srsName in the top two levels in the hierarchy (ie, CompositeCurve and LineString), but not in posList.
I just would like to check in which elements srsDimension and srsName are actually required. In two or all three elements? In just the top element? Is there a hard and fast encoding rule, or is there just a convention?
Senior Geologist - Information Management | Continental Geology Section
Minerals and Natural Hazards Division | GEOSCIENCE AUSTRALIA
Oceania Councillor & Interoperability Working Group
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