[Requests] Comment on revised OGC 08-085r2, OGC GML in JPEG 2000 (GMLJP2)

Rahkonen Jukka (Tike) jukka.rahkonen at mmmtike.fi
Fri Mar 14 07:56:25 EDT 2014

Part A to be completed once.  Iterate Part B as needed.


1. Evaluator:
 Jukka Rahkonen
Planning officer
Information centre of the
Ministry of agriculture and forestry
email jukka.rahkonen at mmmtike.fi

2. Submission: OGC 08-085r2, OGC GML in JPEG 2000 (GMLJP2)
Encoding StandardPart 1: Core


Requirement #1
Make the location of rectifiedGrid origin compared to pixel extents totally clear. It is in the centre of pixel, isn't it?

Implementation Specification Section number #1
16.Coordinate reference systems, page lvii

Criticality #1

Comments/justifications for changes #1
It takes just a few words and there will no place for misunderstanding: Origin of the RectifiedGrid presents the centre point of the corner pixel.


Requirement #2

Give clear examples of valid ways for giving srsName and UoM

Implementation Specification Section number #2
16.Coordinate reference systems
17.Units of measure
18.Reference to UOM definition
In all examples

3. Criticality #2

4. Comments/justifications for changes #3

Throughout the paper srsNames are given in two different ways. 
- srsName="http://www.opengis.net/def/crs/EPSG/0/4326"
- srsName="urn:ogc:def:crs:EPSG::4326"
In one example there is also this variant 
- srsName="EPSG:4326"

I believe that it means that both http and urn versions can be used but it is not told clearly in the document. Perhaps the meaning is to be explicit and not repeat things which are already defined in existing OGC documents. This revised document does have a reference to another document with number OGC 07-092r3 http://portal.opengeospatial.org/files/?artifact_id=30575
However, reading OGC 07-092r3 does not help, that document does not mention at all that  srsName="http://www.opengis.net/def/crs/EPSG/0/4326" could be used but it is having the urn syntax in all examples.

The same kind of thing is with the units of measures. There is a table 3 "URIs for units-of-measure" that gives examples of how to refer to UoM and they are like
- http://www.opengis.net/def/uom/OGC/1.0/metre or
- http://www.opengis.net/def/uom/EPSG/6.3/9001

However, in all the XML examples of this revised standard the UoMs are expressed as
- uom="urn:ogc:def:uom:EPSG::9001"

If both URLs and urn-URIs are allowed, tell it in sections 16, 17, and 18. In addition, check all the XML examples. Now most of them contain both http and urn variants in the same XML document which makes them harder to read and makes reader to wonder it bounding box srsName should be gives with http-URL but rectifiedGrid origin with urn.

Table 3 clearly suggests that http-URL is the preferred way but examples contain only urn:s.

Requirement #3
Correct a typo

Implementation Specification Section number #3

On page lvi there is this section:
<Envelope srsName="http://www.opengis.net/def/crs/EPSG/0/4326" 
axisLabels="Lat Long" uomLabels="deg deg" srsDimension="2">
<lowerCorner>270379.500 3942462.000</lowerCorner>
<upperCorner>518842.500 3942462.000</upperCorner>

Criticality #3

Comments/justifications for changes #3
Obviously a copy-paste error

With best regards

Jukka Rahkonen
Planning officer
Information centre of the
Ministry of agriculture and forestry

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