>#8: Altitude type of 0 == no altitude
>---------------------------------------+------------------------------------
> Reporter: martin.thomson@andrew.com | Owner:
> Type: defect | Status: new
> Priority: major | Milestone:
>Component: rfc3825bis | Version:
> Severity: - | Keywords: altitude
>---------------------------------------+------------------------------------
> RFC 3825 seems to indicate that an altitude type of 0 indicates that there
> is no altitude defined.
RFC 3825 wrote that a vertical datum was not necessary to inform a
client of its altitude. That could either be because the client's
altitude couldn't be determined, or it was withheld.
>This needs to be clearer in the bis.
I agree this should be clearer in the bis.
> Q: is altitude type 0 valid?
It has to be, if the server can't figure out what the altitude of the
client is, then the easiest way to to tell the client this is to use
datum EPSG:4326 and altitude type of '0'.
We could sidestep having 2 WGS-84 datums registered and simply have
4979 delivered with an altitude type of '0', meaning servers only
ever have to remember 1 WGS-84 datum (4979) and if there is an
altitude, include the type (and altitude value). If there is no
altitude value, set the altitude type to 0, which the client converts
to 4326 if it informs another entity its location.
> Q: what meaning is attached to altitude type 0?
IMO - that there is no altitude given (or guessed or whatever)
> Q: what is the impact of having no altitude on the existing datum
> definitions?
In WGS-84, the difference is merely either you're in 2D or 3D.
We could extend that rule to being applicable to all datum pairs. For
example, NAV83 (horizontal) paired with NAVD88 (vertical).
>--
>Ticket URL: <http://trac.tools.ietf.org/wg/geopriv/trac/ticket/8>
>geopriv <http://tools.ietf.org/geopriv/>
>
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