Despike

Description Detect spikes and clean up or mark affected traces.
Module(s) Explorationist Image Gather Processing,
Requirements Gathers, Mutes
Related Trace Mix, Trace Chooser, Header Maths
Works with Gathers

This process detects spikes, and performs actions on the affected traces and/or regions.

Create a Despike process

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

Define Despike settings

Define mute gather settings
  1. Volume: Select the input volume
  2. Region: Select the region that the process is limited to
    • Whole Trace - no limit applied
    • Horizon/Constant - define a starting time or horizon and enter a window length
    • Header - use a header to provide the starting time and enter a window length
  3. Mode: choose the analysis method
    • Peak Magnitude - if a value has magnitude greater than maximum, or less than minimum it is flagged as a spike
    • RMS - if the RMS average of the samples is greater than the value, the window is flagged as a spike
    • Average - if the average magnitude of the samples is greater than the value, the window is flagged as a spike
    • Vertical - compare local regions of a trace to a larger window of the trace using sliding windows
      • Calculate the average of a small window
      • Calculate the average of a long window, excluding the samples in the small window. This long window result is the reference
      • If the short window result is greater than the “Compare factor” times the reference, then flag the short window as a spike
    • Horizontal - compare a trace to its neighbours, over a sliding window
      • For each trace, calculate the average of the absolute values of the window
      • If the result is greater than the “Compare factor” times its neighbours, then flag the short window as a spike
  4. Action: Perform the following when spikes are detected
    • Drop Traces - drop traces containing a spike, leaving NaNs or missing traces
    • Mark Trace as Dead - keep traces, but set the TRID header to 30,000
    • Set custom TRID - keep traces, but set the TRID header to a custom value
    • Mute Spikes - ramp to zero - set spikes to 0 and smooth using the mute radius. Refer to the diagram - green curve
    • Mute Spikes - clip to max values and smooth - set spike values to the Clip Magnitude, and smooth using the mute radius. Refer to the diagram - blue curve
  1. Store max/average etc - Store spike values in a header
    • The stored value depends on the detection algorithm used
    • Where amplitude limits are used, the magnitude of the largest spike is stored
    • For averages and rms, the resulting value is stored
    • The value can be scaled or shifted before storing
  2. The despike result volume is available in the Volume tab