[x3d-public] geoSystem use [was: bug in InstantReality or my code?]

[Andreas Plesch]

Hi John,

I?ve also tried keyValue.  How do I set keyValue in the
> GeoPositionInterpolator?  The standard says I can.
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html
> <
> http://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/geodata.html
> >


When a geospatial node like GeoPositionInterpolator is used it is generally
necessary to define the kind of coordinate system in which coordinates are
provided. By default, coordinate tupels are interpreted as latitude,
longitude, elevation. So the key values '0 0 10 0 0.00628 10' would mean
two points on the equator, one at zero longitude and one at 0.00628 degrees
longitude, both at 10m elevation.

Probably, you had the regular x3d cartesian coordinate system in mind when
you defined these key values. To use a cartesian system, specify
geoSystem=' "GC" ' as a field of GeoPositionInterpolator. Not sure how well
InstantReality supports this. GC stands for geocentric. X and Y are in the
equatorial plane, Z points to a pole. 0,0,0 is at the center of the earth.
So 0 0 10 means a point on the Z axis, 10m away from the origin/center, as
you would expect.

As a side note, if you use great circle interpolation, there are always two
potential paths to connect two points on a sphere. The interpolator will
use the shorter path,

-Andreas

-- 
Andreas Plesch
39 Barbara Rd.
Waltham, MA 02453
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