[Esip-documentation] ACDD comments

Thu Sep 18 17:40:18 EDT 2014

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 
> <mailto: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 <mailto: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.
<>< <>< <>< <>< <>< <>< <>< <>< <>< <><

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.lists.esipfed.org/pipermail/esip-documentation/attachments/20140918/d3ef6eda/attachment-0001.html>