[geovrml] Re: GeoLocation: comments and questions

[Lee Iverson <leei>]

In message <3944A108.1AE365E@ccis.adisys.com.au>, Chris Thorne writes:
>
>If I want to zoom into a digital Earth model from space down to some
>highly detailed house in Queensland, Australia then I can use
>GeoLocation to take care of the precision issues. If I were then to
>zoom out to see the Earth revolving around the Sun then I would need
>a GeoLocation node (used like a Transform node) around Earth,
>adjusting the tansform parameters to keep earth moving.  I see two
>problems here:

I see one main one.  GeoVRML currently uses spatial reference models
based on a fixed earth coordinate system.  As long as you are
navigating with that coordinate system in mind you should be fine.  In
the future, we may extend things to allow for the possibility of
Solar-centric coordinates, but that can only really come with the
addition of a temporal model in order to define the relationship
between the earth-centric and solar-centric coordinates (thus
modelling the earth's rotation and revolution about the Sun).

If you want to use the GeoVRML building blocks for this solar-system
exploration at this point in time, you have no real choice but to
represent the positions of the plantary bodies and Sun wrt. the
fixed-earth geocentric spatial reference model.  Sorry for tossing you
back to pre-Copernican times, but that's what we got right now.

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Lee Iverson     		SRI International
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