gtchart: A program to generate temperature charts.

Usage: gtchart [-i FILENAME] [-c COLUMN] [-o FILENAME] [other options]

Some of the parameter descriptions refer to the temperature
chart on Dr. Roy Spencer's web site:

http://www.drroyspencer.com/latest-global-temperatures

Parameters are not case sensitive.

Parameters are:

 -i FILENAME
 -in FILENAME

     Specifies the name of the input text file containing
     the temperature data. The text file is obtained from:

     http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc.lt

     The default input text file name is "temps.txt".

 -o FILENAME
 -out FILENAME

     Specifies the name of the output graphics file
     containing the rendered temperature chart in Microsoft
     Bitmap (BMP) format. The default is the name of the
     input file with a .BMP filetype. The filename is
     massaged to end with ".bmp".

 -ave N

     Specifies a running average model. N is the radius of
     average. The chart on Dr. Roy Spencer's web site has a
     13 month running average. With this program this is
     specified as "-ave 6". (6+1+6 = 13)

 -fft N

     Specifies an FFT low-pass filter model. N is the radius
     of the number of low frequency terms kept. A value of
     10 produces nice curves. Because the FFT is a periodic
     function the ends of the modeled curve try to meet and
     thus diverge from the data.

 -poly N

     Specifies a least square polynomial model. N is the
     number of terms. A value of 1 produces the average of
     the temperatures. A value of 2 produces the best-fit
     straight line. If a value of two is chosen then the
     temperature trend in degrees per decade is rendered on
     the chart. A value of 20 produces nice curves. Values
     much more than 25 start to show precision problems.

 -c TITLE
 -column TITLE

     Specifies the column title of the input text file to
     chart. The main column titles are:

     Globe   The entire globe
     NH      Northen Hemisphere
     SH      Southern Hemisphere
     Trpcs   Tropics
     NoExt   Northern Extratropic
     SoExt   Southern Extratropic
     NoPol   Northern Polar
     SoPol   Southern Polar
     USA48   U.S.A. contiguous 48 states

     Additionally, all regions except USA48 are broken down
     into land and ocean components. These are specified by
     appending "_Land" or "_Ocean" to the column title.
     Parameter "-c NH_Land" produces a chart of the
     temperatres for the land masses of the northern
     hemisphere.

     The default column is "Globe".

 -d
 -debug

     If the FFT model is requested then the debug parameter
     makes the program generate file "debug.txt" containing
     a listing of the Discrete Fourier Transform
     coefficients.

 -dpi N

     Specifies the resolution of the chart in dots per inch.
     The default is 150 which is good for printing. A value
     of 75 is good for charts displayed on th screen.

 -fs N

     Specifies the font size. The default is 1 which renders
     text characters as 16x8. A font size of 2 renders text
     characters as 32x16.

 -dt N

     Specifies the interval between temperature labels. The
     computer program calculates a value from the temperatue
     data and the size of the chart. Values of 0.05, 0.10,
     and 0.20 are typical.

 -xt N

     Specifies the interval between temperature grid rows.
     The computer program calculates a value from the
     temperature data and the size of the chart. Values of
     0.01 and 0.02 are typical.

 -h
 -help

     Displays this help text.

 -hi N

     Specifies the chart's high temperature. The computer
     program calculates a value from the temperature data.
     The chart on Dr. Roy Spencer's web site has a high
     temperature of 1.2. With this program this is specified
     as "-h 1.2".

 -lo N

     Specifies the chart's low temperature. The computer
     program calculates a value from the temperature data.
     The chart on Dr. Roy Spencer's web site has a low
     temperature of -0.6. With this program this is
     specified as "-l -0.6".

 -q
 -quiet

     By default the program writes text to the standard
     output regarding its progress. This option inhibits
     that.