National Geophysical Data Center Hypsometry Program for ETOPO5

Author:  Dr. Peter W. Sloss
         NOAA-NGDC

What is "Hypsometry"?

Hypsometry is the measurement of the distribution of sea-floor (and
land) elevations as areas covered between specified elevation and
geographic limits. This program computes the area percentages
between given elevations on the Earth's surface, based on data in the
ETOPO5 5-minute gridded bata base. These areas can be used to analyze
distribution of marine environments and percentages of terrain in
elevation ranges above sea level. For example, the percentage of sea
floor between sea level and 200 meters depths is that part of the earth's
surface identified as continental shelf.

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Use of the program:

The program file for DOS PCs is "HYPSO.EXE" and is associated with
the 5-minute gridded elevation file "ETOPO5.DOS" found in the
"\TOPO\ETOPO5" directory on this CD-ROM. 

Before running the program, the PC must be told how to find the
ETOPO5 data file on the CD-ROM. This is done by typing (at the DOS
prompt):

SET ETOPO5=L:\TOPO\ETOPO5\ETOPO5.DOS

This assumes that your CD-ROM drive is designated "L:".  The ".DOS"
extension on the file name identifies the data file that is correctly
formatted for DOS-compatible PCs.

To start the program, type

HYPSO /r 8640

(the "/r 8640" tells the program to set up a memory buffer for the
ETOPO5 raw data being read).

The program will ask for an OUTPUT FILE name, where the results of the
computation will be saved. A carriage return (ENTER key) instead of a
file
name will send the results to your computer screen.

The program next asks for a title name for your results (anything up to
40 characters).

Next, you are asked the number of "bins" or elevation ranges to divide
up the depth range. A zero here tells the program to make all bins the
same size (auto) as specified in the next entry. Otherwise, the elevation
range will be cut up into the number of bins you specify.

The next entry gives the lowest elevation to be considered in the
computations, at the bottom of the lowest bin.

The next entry (if you have selected "auto" equal-sized bins) sets the
bin size.

Next, the maximum elevation, or the top of the highest bin, is requested.
Note that the elevation range being analyzed does not have to span the
entire range of the data base -- you can compute one bin from -200 to 0
meters or between any other limits. 

If you asked for a set number of bins, you will be asked to give their
limits in order from bottom to top. This option allows each bin to be a
different size.

Next, the program requests bounds for 5-degree latitude-longitude squares
of data to be used in the computations.  Select your starting point as
the SouthWest corner of your data area, and answer the request for the
number of 5-degree blocks Eastward and Rorthward from that starting point.
Negative (< zero) entries in the "number of blocks" responses allow you
to mask out part of a 5-degree block -- just answer the questions.

The program will ask if you have additional areas to include in the totals.
If so, the geographic-limits sequence above repeats. If you are ready for
results, the program begins reading the data and computing the results.
A sample computation result appears below:

 Area covers   10. to   30. deg. latitude, and 
              130. to   150. deg. longitude.

 The Hypsometry of your data areas is as follows:
 ----------------------------------------------------- ---------------
 Bin #    from   to  (m)    Area (sq.km)    % of Total       Cum. %
    1   -11000.    -9000.      5222.381        0.11266        0.11266
    2    -9000.    -7000.     80490.630        1.73636        1.84902
    3    -7000.    -5000.   1890583.994       40.78407       42.63309
    4    -5000.    -3000.   2185956.331       47.15590       89.78899
    5    -3000.    -1000.    448597.559        9.67724       99.46623
    6    -1000.     1000.     24743.369        0.53377      100.00000
    7     1000.     3000.         0.000        0.00000      100.00000
    8     3000.     5000.         0.000        0.00000      100.00000
    9     5000.     7000.         0.000        0.00000      100.00000
   10     7000.     9000.         0.000        0.00000      100.00000
    >     9000.                   0.000        0.00000
 Total area of region "Sample Computation                      
" =      4635594.3 sq. km.

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The FORTRAN source code for this program is included in the file
"HYPSO.FOR"