June 2002

The data comes from the nice folks at the USGS, and you may
download some of this data for yourself from the following URL:
	http://www.ngdc.noaa.gov/mgg/global/seltopo.html
The data is described on http://www.ngdc.noaa.gov/mgg/global/etopo5.html.
"Data Announcement 88-MGG-02, Digital relief of the Surface of the 
Earth, NOAA, National Geophysical Data Center, Boulder Colorado, 1988."

The data itself is digital depth/elevation of rectangle 
containing the North American continent. If you like, you
could go to the URL above and grab a rectangle of your
own choosing and use it as input to this program. The range of
data in the sample file ranges from 51 degrees north latitude
to 21 degrees north latitude and 134 degrees west longitude to
66 degrees west longitude. Data values are whole meters, with positive
values representing elevation above sea level, and negative values
representing depth below sea level. The data is a grid of size 871x361 at
a resolution of 5 minutes. The data values begin at the Northwest
corner, progress Eastward for 871 values, then stepping 5 minutes
South for the next row, ending at the Southeast corner. 

The data is represented in ASCII format for portability issues
in this distribution.

ETOPO5 ASCII Data copy...

Area: 
              51 North latitude
                       |
134 West longitude    - -     66 West longitude
                       |
              21 North latitude

Data format:  Datavalues in whole Meters
              (- = below sea level)

Delimiter: space

Grid size: 817 x 361 matrix of 5-minute grid values beginning
           at NorthWest corner progressing Eastward for 817
           values, then stepping 5 minutes South for the next
           row, ending at SouthEast corner.

Note: Negative latitudes are South.
      Negative longitudes are West.

File size: 1418507 bytes.

Notes: To create the file elevData.txt, I obtained the file generated
by the URL above, and using a text editor, stripped off all the
extra stuff before the actual elevation data, and inserted a single
line containing the values "871 361" that describe the width
and height of the elevation rectangle.