[x3d-public] GeoPositionInterpolator revision for V4.0

[Mike McCann]

Should we take these proposed changes to github.

I'm concerned that they'll get "lost" in email.

-Mike

On Apr 28, 2016, at 12:34 PM, Andreas Plesch <andreasplesch at gmail.com> wrote:

> 
> Thanks, Doug and Mike.
> 
> I may add that it looks like that cobweb will offer great circle interpolation (among other geospatial capabilities) in a future release.
> 
> 
> Date: Thu, 28 Apr 2016 07:59:54 -0700
> From: Mike McCann <mccann at mbari.org>
> 
> This seems like a good alternative. Let me propose a prose change for http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html#GeoPositionInterpolator:
> 
> The GeoPositionInterpolator node provides an interpolator capability where key values are specified in geographic coordinates and the interpolation is performed within the specified spatial reference frame.
> 
> becomes:
> 
> The GeoPositionInterpolator node provides an interpolator capability where key values are specified in geographic coordinates and the interpolation is performed within the specified spatial reference frame. Great circle interpolation is recommended, future specifications will require great circle interpolation.
> 
> 
> Thanks, good prose. It may be help to explain a bit what great circle interpolation is about. Something like:
> 
> Interpolation along a great circle route is recommended[ for reproducibility between spatial reference frames][? and browser implementations?]. Future specification will require such great circle interpolation.
> 
> 
> The new sentence for version 4 of the spec. could be:
> 
> Interpolated values are required to follow a great circle.
> 
> 
> Nice. Perhaps add route as in great circle route ?
> Should there be a hint for a recommended algorithm as well ? I am thinking about SLERP since it works very well and efficiently between key values after being converted to geocentric vectors.
> 
> -Andreas
>  
> -Mike
> 
> On Apr 28, 2016, at 6:14 AM, doug sanden <highaspirations at hotmail.com> wrote:
> 
> >
> > Andreas,
> >
> >> Alternatively, rather than introducing a new field it may suffice to
> >> simply clarify in the appropriate spec. section that by default great
> >> circle interpolation is recommended for consistency across geoSystems
> >> and across browsers. This could be a recommendation  and not a
> >> requirement but possibly with a qualifier that future spec. revisions
> >> will actually require great circle interpolation.
> >
> > Sounds good.
> > -Doug
> > BSc Surveying Engineering
> >
> >
> >
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> Andreas Plesch
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