Services Vertical Extent guidance references datasets

agiorguk / gemini

Resources relating to the UK Gemini metadata profile

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Services Vertical Extent guidance references datasets #123

Open archaeogeek opened 8 months ago

archaeogeek commented 8 months ago

I think we need to review in detail the Purpose and Meaning, and the Guidance, so it is clear exactly how this element should be applied to metadata for services. Currently, I believe its unclear e.g. is the element to record the vertical domains of each data resource the service operates on, or is it something else?
Encoding guidance note 1 is extremely verbose and ambiguous in my opinion. Think it also needs to be re-assessed and re-worded for clarity.
Encoding guidance note 2 quotes "must be provided in order to give meaning to the minimum and maximum coordinates". There is not a useful subsequent sentence detailing what "in order" means.
Encoding examples 1 and 2 use MD_DataIdentification when they should be using SV_ServiceIdentification

nmtoken commented 8 months ago

Agree that examples should use <srv:SV_ServiceIdentification> instead of <gmd:MD_DataIdentification id="XYZ-...">

nmtoken commented 8 months ago

Currently, I believe its unclear e.g. is the element to record the vertical domains of each data resource the service operates on, or is it something else

Agree that some clarification may be in order. My reading is it is the vertical extents of the data as exposed by the service, which may not be the same as vertical extents of the data operated on; the same clarification should accompany other extents descriptions (temporal, extent, bounding box), that is a service may apply some restrictions to the extents it offers for any dataset it operates on.

nmtoken commented 8 months ago

Encoding guidance note 2 quotes "must be provided in order to give meaning to the minimum and maximum coordinates". There is not a useful subsequent sentence detailing what "in order" means.

The original guidance note (http://ogcdev.bgs.ac.uk/AGI/gem23-sv.html#44) was:

The CRS of vertical extent elements must be provided in order to give meaning to the minimum and maximum coordinates. From the CRS, for example, it is possible to determine the orientation of the coordinate system axis (i.e. do positive values increase upwards or downwards from the zero reference) and the units of the coordinate values.