Re: Ontology for points in a three-dimensional space

On 9 Dec 2008, at 14:05, Norman Gray wrote:

> In this context, x, y, z would usually (or most conventionally) be  
> linear coordinates with an origin at the centre of the body, such  
> as the earth.  On the other hand, latitude and longitude would be  
> angular coordinates, and altitude a radial coordinate above the  
> earth's reference surface, also centred on the earth.  Thus  
> coordinate (0,0,0) would be the centre of the earth in (x,y,z)  
> coordinates, and the point on the equator south of Greenwich in  
> (long,lat,alt) coordinates.  Thus they can't really be subProperties.


ungeo:x, ungeo:y and ungeo:z are defined as numerical points on the  
x, y and z axes. There is no requirement for the axes to be linear;  
and definitions of the axes may include the units used.

For example, my current location could be written as:

<#location> a ungeo:Point ;
	ungeo:x -0.0009 ;
	ungeo:y 50.87318 ;
	ungeo:z "55"^^<dbpedia:Approximation> ;
	ungeo:system <#wgs84> .

<#wgs84> a ungeo:ReferenceSystem ;
	rdfs:label "WGS84" ;
	ungeo:x-axis "Degrees West of the line running
			from the North pole to the South
			pole through the observatory at
			Greenwich, measured as an angle
			from the centre of the Earth." ;
	ungeo:y-axis "Degrees North of the equator,
			measured as an angle from the
			centre of the Earth." ;
	ungeo:z-axis "Metres above sea level." ;
	ungeo:body <dbpedia:Earth> .

The idea is to be able to represent any numerical (x,y,z)  
coordinates, in any reference space - the reference space doesn't  
need to have three traditional perpendicular axes. It can even cope  
with weird spaces like <http://buzzword.org.uk/2008/torus-space>.

<#p1> a ungeo:Point ;
         ungeo:x 0.2 ;
         ungeo:y 1.3 ;
         ungeo:z 3.6 ;
         ungeo:space [ rdfs:isDefinedBy </2008/torus-space> ] .

-- 
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>

Received on Tuesday, 9 December 2008 15:23:59 UTC