It is not a question of just
differencing - since we will in fact know the local coordinates much
more accurately than the coordinates of the position of the object
relative to the earth.
Also, as Anselm mentioned, another hugely important case for AR is
multiple instancing. The notion of "global coordinates" of the features of
a manufactured item that has many instances makes no sense.
And an observation: For moving objects, the underlying reason that local
representation is sensible is that the local coordinates of features are the
invariant facts - facts that will remain true over indeterminate motions in
the future, unlike global coordinates however well known at any particular
time.
-- Chris
----- Original Message -----
From: "Ron Lake" <[email protected]>
To: "Christian Willmes" <[email protected]>
Cc: "geojson" <[email protected]>; <[email protected]>;
"GeoRSS" <[email protected]>
Sent: Tuesday, September 01, 2009 12:05 PM
Subject: Re: [georss] [Geowanking] [Geojson] simple 3D geocode for AR
If precision, convenience are of no interest than yes a (x,y,z)
Geocentric CRS will work - but differences in typical large scale
applications will be very small. If your application recognizes (e.g.
image processing) some object in the environment - it would be normal to
specify things relative to the object (e.g. labels, measures on the
object etc) and these are more sensibly expressed in a local coordinate
system (typically rectilinear) - you may not know the accurate location
of the object itself (nor its orientation) - but you only care about its
approximate location (e.g. via GPS) and then the more precise location
of things relative to the object. It is not a question of just
differencing - since we will in fact know the local coordinates much
more accurately than the coordinates of the position of the object
relative to the earth.
R
-----Original Message-----
From: Christian Willmes [mailto:[email protected]]
Sent: September 1, 2009 11:50 AM
To: Ron Lake
Cc: geojson; [email protected]; GeoRSS
Subject: Re: [Geowanking] [georss] [Geojson] simple 3D geocode for AR
Christian Willmes schrieb:
Hi all,
every single (not moving) point on earth
sorry, I don't know why I wrote that... You can surely also model moving
objects in a Geocentric Spatial Reference Frame...
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