# Re: Ontology for points in a three-dimensional space

From: Toby A Inkster <tai@g5n.co.uk>
Date: Tue, 9 Dec 2008 15:23:15 +0000
Cc: Semantic Web <semantic-web@w3.org>
To: Norman Gray <norman@astro.gla.ac.uk>
```
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

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