Re: orthophoto over dem

• To: Antonello Andrea <andrea.antonello@xxxxxxxxx>
• Subject: Re: orthophoto over dem
• From: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Date: Mon, 6 Nov 2006 05:27:23 -0600 (CST)

> 1) what is the actual development status of visad? The update status on
> the webpage says Wed Feb 15 14:21:41 CST 2006, so I'm full of hope.

VisAD is very actively developed, and is the
basis of a number of other systems such as
Unidata's IDV, SSEC's McIDAS V and UW's VisBio.

> 2) The real question: I'm trying to overlay a orthophoto over a dem, but
> after a lot of struggling around and no luck I need some help. I'm
> talking about maps in metric units and not degree.
> Is there an example I possibly couldn't find to see how it is done
> properly?
> I browsed throught the documentation and the mailinglists, but wasn't
> able to understand properly, also most of the posts are from 1999, so
> I found some classes not to be there any more.
> My last try was that to modify the ShadowImageFunctionTypeJ3D, but that
> doesn't seem to be the right approach.

That isn't the right approach. You need to define
an extension class of visad/CoordinateSystem.java
that defines the mappings of your photo coordinates
to and from earth reference coordinates (assuming
the domain of your dem is in earth coordinates),
and use this class in the domain Set of your image
FlatField.

Then you need to put your dem FlatField and your
image FlatField in a Field[] array, and pass this
to the FieldImpl.combine() method. This will remap
them to a common domain (the domain of the first
FlatField in the array) and return a FlatField
with range components for both image and dem. Then
display this with the dem component ScalarMap'ed to
ZAxis and the image component ScalarMap'ed to RGB.

See Section 4.1 of the VisAD tutorial for an example
of displaying color over a topography.

Good luck,
Bill

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    • From: Andrea Antonello
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