[Esip-documentation] ACDD comments

Thu Sep 18 17:59:03 EDT 2014

Hi Bob,

I don't think your questions appear dense, far from it.  I also sense that
your questions/comments are in part related to the difficulty of making
changes to code based on evolving standards.  This is a legitimate concern
and can be part of the discussion IMO, correct me if this assumption is
wrong.

In terms of the actual standards which indeed are often verbose in the OGC
space,  below is a complex WKT example taken from GeoAPI which is a Java
based reference implementation for many of OGC's standards (see
http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html).
 I have a feeling that this may generate more questions around the
complexity of supporting WKT for applications which use ACDD, but I think
will at least reveal that WKT is a viable way to express geometries.
 Developing standards and consensus is hard I guess.

Dave

COMPD_CS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#COMPD_CS>["OSGB36
/ British National Grid + ODN",
    PROJCS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PROJCS>["OSGB
1936 / British National Grid",
        GEOGCS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#GEOGCS>["OSGB
1936",
            DATUM
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#DATUM>["OSGB_1936",
                SPHEROID
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#SPHEROID>["Airy
1830",6377563.396,299.3249646,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","7001"]],
                TOWGS84
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#TOWGS84>[375,-111,431,0,0,0,0],
                AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","6277"]],
            PRIMEM
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PRIMEM>["Greenwich",0,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","8901"]],
            UNIT
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#UNIT>["DMSH",0.0174532925199433,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","9108"]],
            AXIS
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AXIS>["Lat",NORTH],
            AXIS
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AXIS>["Long",EAST],
            AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","4277"]],
        PROJECTION
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PROJECTION>["Transverse_Mercator"],
        PARAMETER
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PARAMETER>["latitude_of_origin",49],
        PARAMETER
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PARAMETER>["central_meridian",-2],
        PARAMETER
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PARAMETER>["scale_factor",0.999601272],
        PARAMETER
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PARAMETER>["false_easting",400000],
        PARAMETER
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#PARAMETER>["false_northing",-100000],
        UNIT <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#UNIT>["metre",1,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","9001"]],
        AXIS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AXIS>["E",EAST],
        AXIS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AXIS>["N",NORTH],
        AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","27700"]],
    VERT_CS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#VERT_CS>["Newlyn",
        VERT_DATUM
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#VERT_DATUM>["Ordnance
Datum Newlyn",2005,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","5101"]],
        UNIT <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#UNIT>["metre",1,AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","9001"]],
        AXIS <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AXIS>["Up",UP],
        AUTHORITY
<http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","5701"]],
    AUTHORITY <http://www.geoapi.org/3.0/javadoc/org/opengis/referencing/doc-files/WKT.html#AUTHORITY>["EPSG","7405"]]

On Thu, Sep 18, 2014 at 3:40 PM, Bob Simons - NOAA Federal <
bob.simons at noaa.gov> wrote:

>  Hmmm.  I'm sorry to be so dense.  I see a 93-page document and the
> closest I can find to an answer about how to specify units for the numbers
> in a WKT geometry is the vague statement
> "NOTE In a coordinate reference system, the numbers shall be qualified by
> units."
> All the examples I see, e.g., pg XIX, lack units.
> (ACDD references Wikipedia http://en.wikipedia.org/wiki/Well-known_text,
> but I see no mention of units there, nor do any of the examples have
> units, nor do I see there how to specify a coordinate system within a WKT
> geometry.)
>
> And if I look at the BNF notation for a point in the OGC document
>   <point> ::= <x> <y>
> I see
>   <x> ::= <signed numeric literal>
>   <y> ::= <signed numeric literal>
> but no units.
>
> I do see a separate section in the OGC document for specifying a
> coordinate system. Is ACDD's geospatial_bounds tied firmly to some other
> ACDD attribute which specifies the coordinate system?  Or I am just unable
> to find the specification for specifying a coordinate system within a WKT
> geometry?
>
> Or, can you please just give me geospatial_bounds example (WKT which
> specifies units and a coordinate system) and add it to the ACDD
> specification)?
>
> Or if the units are assumed to be (must be) degrees_east, degrees_north,
> meters above the geoid, and uses the WGS 84 coordinate system, then please
> say so in the ACDD specification. (Z datums for the ocean are notoriously
> hard. Most in-situ measurements are not relative to the geoid and many
> don't use WGS 84.)
>
> Thank you.
>
>
>
> On 2014-09-18 1:14 PM, David Neufeld - NOAA Affiliate wrote:
>
> Hi All,
>
>  Below is a link to the OGC Simple Features Specification which includes
> how to represent features as Well Known Text.  You will find
> representations that include z values, units and coordinate systems.
>
>  http://portal.opengeospatial.org/files/?artifact_id=25355
>
>  hth,
> Dave
>
> On Thu, Sep 18, 2014 at 11:59 AM, John Graybeal via Esip-documentation <
> esip-documentation at lists.esipfed.org> wrote:
>
>> As the person most involved in several of these, I guess I will respond
>> as best I can.
>>
>>  On Sep 18, 2014, at 09:26, Bob Simons - NOAA Federal <
>> bob.simons at noaa.gov> wrote:
>>
>> * For geospatial_bounds, WKT doesn't specify units. So it is unclear if
>> the WKT values represent latitude and longitude, or x and y from some
>> projection (which opens up a huge can of worms). Please either require the
>> use of latitude and longitude (please) or make some provision for
>> specifying units (good luck with that).
>>
>>
>>  OK, I'm guessing we'll have to look into this. Thanks for pointing it
>> out. WKT is not specified well in Z either, if I recall correctly.
>>
>>
> --
> Sincerely,
>
> Bob Simons
> IT Specialist
> Environmental Research Division
> NOAA Southwest Fisheries Science Center
> 1352 Lighthouse Ave
> Pacific Grove, CA 93950-2079
> Phone: (831)333-9878 (Changed 2014-08-20)
> Fax: (831)648-8440
> Email: bob.simons at noaa.gov
>
> The contents of this message are mine personally and
> do not necessarily reflect any position of the
> Government or the National Oceanic and Atmospheric
> Administration.
> <>< <>< <>< <>< <>< <>< <>< <>< <>< <><
>
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