SAC Command Reference Manual

TAPER

SUMMARY

Applies a symmetric taper to each end of data.

SYNTAX

TAPER {TYPE HANNING|HAMMING|COSINE},{WIDTH v}

INPUT

TYPE HANNING:Apply a Hanning taper.
TYPE HAMMING:Apply a Hamming taper.
TYPE COSINE:Apply a cosine taper.
WIDTH v:Set the taper width on each end to v. This is a value between 0.0 and 0.5.

DEFAULT VALUES

TAPER TYPE HANNING WIDTH 0.05

DESCRIPTION

A taper is a monotonically varying function between zero and one. It is applied in a symmetric manner to the data such that the signal is zero for the first and last data points and increases smoothly to its original value at an interior point relative to each end.

The COSINE option here is computed using the sin() function as:

DATA(J) = DATA(J) * SIN(OMEGA*J) where OMEGA = PI/(2*N)

where N is the length of the taper on each end, and J runs from 1 to N.

The general form for the Hanning or Hamming taper is:

DATA(J)=DATA(J)*(F0-F1*COS(OMEGA*(J))

This equation would be applied to the left-hand side of each signal. A symmetric one is applied to the right hand side. The following table defines the various parameters used in the different tapers.

TYPE OMEGA F0 F1
HANNING PI/N 0.50 0.50
HAMMING PI/N 0.54 0.46

ERROR MESSAGES

  • 1301: No data files read in.
  • 1306: Illegal operation on unevenly spaced file

HEADER CHANGES

DEPMIN, DEPMAX, DEPMEN

LATEST REVISION

January 15, 1985 (Version 9.10)