Introduction WXXM Coverage Representation
Copyright © 2012 Open Geospatial Consortium
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Figure 6: The WXXM Coverage structure
Figure 6 shows the concrete instantiable coverage types defined in WXXM.
Figure 7: The WXXM coverage hierarchy
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Copyright © 2012 Open Geospatial Consortium
With the WXXM coverage hierarchy shown in Figure 7, it appears that it doesn’t align closely with the ISO 19123 definitions. For example, the WXXM PointCoverage
corresponds to the ISO 9123 CV_DiscretePointCoverage; WXXM ProfileTimeSeries does not have a correspondence in ISO 19123; etc.
The Northrop Grumman Technical Paper suggests that “the main issue in dealing with the above types of data has been that the ISO coverage model specifically restricts
coverages to 4D 1-3 spatial dimensions and 0-1 time dimension”. This report is specifically focused in scope on dealing with the two data types i.e. Forecast model runs
and Radar data and encoding them into an ISO 19123:2005 compliant coverage. The position postulated by the weather community, referred to in Annex B: OWS-8 section
4.5.2.3.2 is that if additional dimensions are required in order to record this information, the resulting artifact would be non-compliant with the ISO 19123:2005 coverage model.
Here again the question is that of domain versus range. The ISO 19123:2005 specification limits the domain collection of direct positions to the four spatial-temporal
dimensions as previously noted.
On a side note, there seem to be some copy-and-paste errors resulting from copying and modifying GML schema code. For example, DiscreteCoverage wxCoverage.xsd is
documented as “This element serves as the head of a substitution group which may contain any discrete coverage whose type is derived from gml:DiscreteCoverageType”
whereas this element certainly is not meant to be in the gml namespace.