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Re: Ontology for points in a three-dimensional space

From: Norman Gray <norman@astro.gla.ac.uk>
Date: Tue, 9 Dec 2008 11:51:24 +0000
To: Toby A Inkster <tai@g5n.co.uk>
Message-Id: <9D29AA5A-36F9-4327-9FA1-495CC7F34CB6@astro.gla.ac.uk>
Cc: John Graybeal <graybeal@mbari.org>, Semantic Web <semantic-web@w3.org>


Toby, hello.

On 2008 Dec 9, at 07:39, Toby A Inkster wrote:

>> It would appear the people working on SWEET have thought about it:
>>  http://sweet.jpl.nasa.gov/2.0/spaceCoordinates.owl
>> I particularly notice Cartesian is pretty similar to what you've  
>> suggested.
>
>
> That looks exactly like what I'm after - thanks.

A potential problem is that SWEET is potentially a bit too upper-level  
for what it sounds like you want.  In particular #Cartesian doesn't  
appear to refer to a reference system.  Also, unless you're talking  
about a projection (ie, a map), you want a non-cartesian coordinate  
system for the lunar surface, rather than a plane.

A possible alternative is STC <http://www.ivoa.net/Documents/latest/STC.html 
 >. This has a _lot_ more detail than SWEET, and is expressly designed  
as a solution to the problem you describe, but there is not as yet a  
great deal of software support for it.  (Also, STC is defined as an  
XSchema -- if you're interested, I could roll you an RDFS version of  
it).

FITS has world-coordinate system support, with lots of software  
support, and pulling that into the ontological world is one of my  
'real soon now' projects.

Given that you want something more informal, it sounds like the most  
appropriate thing would be just:

@base <urn:example#>.
@prefix coord: <http://sweet.jpl.nasa.gov/2.0/spaceCoordinates.owl#>.
<#MyLunarCoordinates> a rdfs:Class;
   rdfs:subClassOf coord:Geographic;
   rdf:comment "Coordinates with respect to <http://adsabs.harvard.edu/abs/2002cosp...34E1305W 
 >".

...which gives coord:Longitude, coord:Latitude, coord:Vertical.  Note  
that there are multiple lunar coordinate systems, as that abstract  
notes.  I'm not sure, off the top of my head, how to identify the  
current IAU-endorsed one (if there is one), or indeed how to find the  
definition of the coordinate system referred to in that abstract  
(which may have been a kite being flown).  There's a mention of lunar  
geodesy in [1], but this is starting to get fiddly all over again...

All the best,

Norman

[1] http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/10527/1/02-2551.pdf


-- 
Norman Gray  :  http://nxg.me.uk
Dept Physics and Astronomy, University of Leicester
Received on Tuesday, 9 December 2008 11:52:02 GMT

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