Reuse basic geo vocabulary properties?

There is a simple RDF vocabulary for WGS84 geo positioning that defines the latitude/longitude/altitude properties [here](http://www.w3.org/2003/01/geo/wgs84_pos#). Asuming that `geo` points to that namespace, we can reuse the following properties:

- `geo:lat`: latitude
- `geo:long`: longitude
- `geo:altitude`: altitude (I think it is the same as `schema:elevation` looking at [this issue](https://github.com/schemaorg/schemaorg/issues/113))
- `geo:location`: The relation between something and the point, or other geometrical thing in space, where it is.

It also defines the classes:
- `geo:SpatialThhing`: Anything with spatial extent
- `geo:Point`: a subclass of `geo:SpatialThing` which is typically described using a coordinate system, such as WGS84.

Note that the vocabulary contained initially `geo:time` but it was later removed in 2009.

We may consider reusing those properties/classes in viadeSpec.

Review the viadeSpec model and the linked WGS84 vocabulary to determine how the proposed properties and classes would fit. Done means reaching a documented decision about whether to reuse them in viadeSpec; no files or tests are named in the issue.

Written by the indexing model from the issue text.