kishore
DEMs (Digital Elevation Models) are raster data structures commonly
encountered in the field of GIS (Geographic Information Systems)- the
other data structure prevalent in GIS is vector, akin to what is produced
by a CAD program. A search for any of these terms will probably give you
the background you need. I like the USGS GIS site for its brevity...
http://info.er.usgs.gov/research/gis/title.html
Specifically, you can find the file specification for DTEDs- which is a
raster data structure developed and used by NIMA (National Mapping and
Imagery Agency)- at the following site. It also contains specs for other
federal spatial data formats...
http://164.214.2.59/publications/specs/index.html
Arc/Info is the leading commercial GIS software package (to say this I
must distinguish between a GIS package and a CAD program). The
fundamental difference between GIS and CAD is great, but essentially in a
GIS spatial data is capable of storing topological information which
allows for spatial operators such as union, intersect, and dissolve to be
applied to the data. In the context of your message- "arc Info binaries"
probably refer to the raster data structures available in Arc/Info-
called grids. Grids are essentially two-dimensional matrices which can
store additonal z-values (attributes) at every point in the grid. The
grid format is a binary proprietary format and is not a published
standard. I do know of one person- Frank Warmerdam- who has attempted to
reverse engineer this format...
http://gdal.velocet.ca/projects/
Hope this helps.
marco morais
ucsb geography
On Tue, 18 Jan 2000, kishore puvvada wrote:
> Pete, Hi,
> thanks for the info. Now a more basic question, Can u
> recommend general informational site/link on the terms
> you have used - bear with me, I am absolutely new to
> this field, but DEM files interest me a lot.
>
> "DTED"
> "ArcInfo Binary"
>
> Please help! :)
> thanks,
> kishore
>
> --- Pete Tinker <[EMAIL PROTECTED]> wrote:
> > I use NIMAMUSE (free at least to US citizens) to
> > convert the DTED data to
> > ArcInfo Binary format. The result has the
> > non-geometry information stripped
> > off, and it loads VERY quickly because it's binary.
> > Read it in, compute
> > normals, stripify it, add texture coordinates if you
> > like, and you're done. I
> > think it took me five lines of code (after I read
> > the file, that is).
> >
> > kishore puvvada wrote:
> >
> > > hello,
> > > I am new to j3d API and understand DEM even less.
> > >
> > > Can anyone recommend DEM loader APIs that they
> > have
> > > used? I tried using Portfolio from NCSA
> > >
> >
> http://www.ncsa.uiuc.edu/~srp/Java3D/portfolio/index.html
> > > to load a DEM image but having some problems.
> > >
> > > I came across another viewer API at:
> > >
> >
> http://www.geogr.uni-jena.de/~p6taug/demviewer/demv.html
> > >
> > > But I haven't been able to understand (it uses
> > another
> > > sw called VisAD) how to use it in a plain j3d
> > program.
> > >
> > > I have specific questions in case someone has used
> > > either of the above. If you have used any other
> > APIs,
> > > I would like to hear from you.
> > >
> > > Any advice will be greatly appreciated.
> > > thanks,
> > > Kishore
>
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