Autocorrelation

Description Correlate a volume with itself.
Module(s) Image Gather Processing, Gather Attributes
Requirements Volume
Related Cross correlation
Works with 2D, Stacks, Gathers

Autocorrelation identifies periodicity in a signal, e.g. air gun bubble, reverberations and multiples. It is useful for detecting repeating periods within signals in the presence of noise.

At each lag value, the signal is correlated with a time-shifted copy of itself. The autocorrelation result is often normalised such that the value at zero lag is 1.

Create Autocorrelation process

Create autocorrelation process
  1. In the Control Panel, open the Process tab.
  2. Click the blue "+" icon and select New Process.
  3. Search and double-click Autocorrelation.
  4. Type a name for the process and click OK.

Define Autocorrelation settings

  1. Volume: Select the data to autocorrelate.
  2. # of lags: The number of correlations (shifts by sample interval) to compute in the autocorrelogram.
    • This includes the zero shift. e.g. "# of lags" = 3 gives an autocorrelogram with lags of 0, 1 and 2 samples).
    • The number of lags determines the output trace length in samples.
    • The zero lag will be at time 0.
  3. Normalise: Normalise the result so the zero lag autocorrelation is 1.
  4. Trace windowing: Calculate the result for the full trace or a window
    • Windowed
      • Start of window: The start time/distance or horizon of the window.
      • Window Length: The length of the input volume window.
    • Entire Trace
  5. As a result of this process, a new volume is available in the Volume tab.

Example of autocorrelation

Nice example of a strong zero phase event at 0 ms with little noise in the data below. No coherent events below suggesting residual noise was removed.

Example of autocorrelation