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\lfoot{Paul Coddington, NPAC, paulc@npac.syr.edu}
\rfoot{Oct 94, CPS713-GIS-\thepage}

\begin{document}

\title[Terrain rendering]%
      {Terrain Rendering for a \\ 
       Geographic Information System} 

\author{Paul Coddington}
\organization{Northeast Parallel Architectures Center}
\date{November 1994}

\titlepage

\section{The Living Textbook}

\begin{slide}
\subsection{\bf Overview of the project} 

The Living Textbook Project is a joint project between the Northeast Parallel 
Architectures Center (NPAC), the School of Education at Syracuse University,
NYNEX, and Columbia University, on the application of high performance
computing and communications (HPCC) to K-12 education.

Several pilot projects involve designing multimedia educational
applications, including interactive simulations, which will be hosted
on computing facilities at NPAC and delivered to schools in Syracuse and
other parts of New York state via the NYNet fast ATM network. 
This is a prototype for the use of the National Information Infrastructure
(better known as the Information Superhighway) for education.

\end{slide}


\begin{slide}
\subsection{\bf The Interactive Journey} 

As a part of the Living Textbook project, we are developing a 
flight simulator interface to geographical data of New York state. 
Students will be able to ``fly'' around a rendered 3D view of the state 
that is interfaced to a Geographical Information System, so that they
can select landmarks and cities and obtain multimedia information
about these places. 

Currently high-quality real-time 3D terrain rendering is not feasible on single
processor workstations, and certainly not on machines such as Macs that are 
likely to be used in schools. 
So we are aiming to interface existing 3D GIS software
running on a Mac with a parallel terrain renderer running on a 
high-performance parallel computer connected via a fast ATM network.

\end{slide}


\begin{slide}
\subsection{\bf Geographical Information Systems} 

The United States Geological Survey (USGS) defines a 
Geographical Information System (GIS) as
{\parskip=0pt
\begin{quotation}
\noindent
   ``a computer system capable of
   assembling, storing, manipulating, and displaying geographically
   referenced information, i.e. data identified according to their
   locations.''
\end{quotation}
}

Many types of geographical data can be used:
{\parskip=0pt
\begin{itemize}
\item Elevation 
\item Satellite image 
\item Digital line graph 
\item Land use / Land cover
\item Geographic place names
\end{itemize}
}
Integrating these different data sets is a non-trivial problem.

\end{slide}


\section{Sources of Terrain Data}


\begin{slide}
\subsection{\bf Elevation data} 

Elevation data is available from USGS as a Digital Elevation Model (DEM).
This is obtained by digitizing contour lines on USGS topographical 
1:250,000 scale maps.
The data is set up as points on a grid covering a 1 degree quadrant 
with 90m resolution. 
30m resolution data is being developed, but currently is only available
for about half the US.

Data for New York state requires about 500 Mbytes, % ??
for the entire US it is about 10 Gbytes.
This will increase 9-fold for 30m resolution data.

The US Defense Mapping Agency has 90m resolution data for the entire world,
but it is classified. The only available world-wide data has 1km resolution,
which is the same as is available for Mars!

\end{slide}


\begin{slide}
\subsection{\bf Example DEM data} 

{\Smallsize
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2D image, with brightness increasing with height.
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\centerline{\psfig{figure=tumwater.dem.ps,width=4.0in}}
\centerline{3D image with shadowing.}
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}

\vspace{1cm}
Digital Elevation Model (DEM) data for part of the Cascade mountains
in Washington state.

\end{slide}


\begin{slide}
\subsection{\bf Satellite image data} 

Landsat satellite data of will provide realistic colors and texture 
for the polygons, with a resolution of 30m. 

Data first has to be 
preprocessed to correct for distortion caused by for varying elevations,
using the DEM data, so that it becomes like a 2D map.
The satellite image data can then be ``draped'' over the DEM data to 
make a 3D image.

Satellite image data at better than 1km resolution is available for Mars 
and Venus from JPL.

\end{slide}


\begin{slide}
\subsection{\bf Example satellite image data} 

\vspace{1em}

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\centerline{\Smallsize Landsat image of Cape Cod}

\end{slide}


\begin{slide}
\subsection{\bf Digital Line Graphs} 

Digital Line Graphs (DLG) are made up of vector data marking objects such 
as roads, waterways, city, county, state and country borders. 

\vspace{1em}

\begin{figure}[h]
\centerline{\psfig{figure=dlg.ps,width=4in}}
\end{figure}
\centerline{\Smallsize Digital line graph of roadways}

\end{slide}


\begin{slide}
\subsection{\bf Other data} 

{\bf Land use / Land cover} data is available from USGS.
Areas are classified into 92 categories of land use (human activity such
as residential, agricultural, etc) and land cover (vegetation, water, etc).

{\bf Geographic place name} data is available from USGS, listing
all known places, features and areas in the US that are identified by
proper names. The database contains over 2 million place names
referenced by geographic position.

\end{slide}


\end{document}


