Geopsy: Correlations

Correlations pop-up window

Correlations, reached from the Waveform menu, computes the correlations of the signals in the active signal viewer with the requested signals.

Parameters

By clicking on Correlations, a pop-up window appears with the following options:

• Maximum time delay controls the size of the output window. The value m is in seconds. The correlations are displayed between -m and +m.
• Choice of the signal to correlate with the active signals. The possibilities are:
  • Between all pairs of signals will compute all the parts of the correlation matrix, i.e. the correlation of each signal of the active signal viewer with each other.
  • With a reference signal will compute the correlation of each signal of the active signal viewer with the selected signal in the pop-up menu (one line of the correlation matrix). It is only possible to correlate the signals with one of them.

Correlations modifies the temporary signal.

Warning: The correlation of signals with a different starting and ending times cannot be computed. In such a case, it is needed to first cut the signals.

Example of correlations between signals

Use of correlation

Correlation between 2 signals (c.f. Cross-Correlation) provides many different informations. The two basic one are the following :

• the maximum in time gives the time delay between two signals.
• The spectra of the cross-correlations is the cross-power spectra. It enhances the frequencies common to the two signals.

See also

• Cross-Correlation (Wikipedia)