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Users Manual for Program PSD

Table of Contents

   Internal calculation procedure
   Input data commands


Program PSD calculates the power spectral density of a time-domain variable and writes the result on file UTFIL.

See also:

TRC_IPSD Recreate track irregularities from a PSD-spectra

Internal calculation procedure

Program PSD reads data from INFIL, the PSD-spectra is generated by Fourier transformation of the auto-correlation spectra. The spectra will pass a Hanning window in order to make the spectra smoother.

Input data commands

Input data are read in free format, valid separators between the input values are <space>, <comma>, <tab>, <equal sign> or <carriage return>. The commands can be written both in lower and upper case letters. The operation of the program is controlled by the commands described below; some of the commands also need arguments.

Commentary line.
Declared= Character*80    Default= Blank

Format in which file UTFIL shall be written.
The string should be written in FORTRAN, and shall be enclosed in parenthesis.
Declared= Character*80    Default= '(1P, E15.6, 5X, E15.6)'

Format in which file INFIL shall be read.
The string should be enclosed in parenthesis e.g. '(E15.6, 5X, E15.6)'. The format specification shall be written in a way that it will fit into the FORTRAN read statement. The format specification given in the example above makes program PSD to read the first 15 characters in file INFIL into the X-variable, the next 5 characters will be skipped, the next 15 characters will be read into the Y-variable.
If FORMIN is given the value 'SNGL', file INFIL will be read in free format.
Declared= Character*80    Default= SNGL

File containing the input data curve.
File INFIL consists of value-pair Xvar and Yvar. The file is read according to the format given in FORMIN. Lines starting with the #-sign are considered as being commentary lines.
Declared= Character*80    Default= Blank

Name of output data file.
The file is written according to the format given in FORMF.
Declared= Character*80    Default= Blank

Amount of displacement when calculating the auto-correlation.
A large XMOVE gives a better accuracy but longer execution time. XMOVE cannot be bigger than the length of the curve in INFIL multiplied by two.
Declared= Real*4    Default= 300 [m]

Starting coordinate when reading INFIL.
Declared= Real*4    Default= 0. [m]

End coordinate when reading INFIL.
Declared= Real*4    Default= 1.E20 [m]

Command which terminates further input data reading.


Following example: Master.psdf can be used as input data file:

##    Input data for program "psd"
  XMOVE= 150  XSTART= 0  XSTOP= 1.E20

  INFIL = ucat/cos_l5d2.sngl

  FORMF= '(1p,e15.6,5x,e15.6)'
  UTFIL= ucat/cos_l5d2.psd