|
<< Click to Display Table of Contents >> Navigation: Statics > Shift gather by raw header |
The Shift Gather by Raw Header module applies a per-trace time shift to an in-memory seismic gather using shift values encoded in raw SEG-Y trace headers (byte-position headers). For each trace, the module reads specified raw header bytes from the linked raw trace vector, evaluates a mathematical expression to compute the shift in ms, and moves each trace accordingly. Unlike the file-based Shift Data by Raw Header module, this module operates on gathers that are already loaded into memory as part of a processing workflow, making it suitable for inline real-time processing of common-midpoint (CMP) or shot gathers.
The shift can be applied in the forward (positive) or reverse (negative) direction, and optionally with linear interpolation for sub-sample precision. Multi-threaded execution is supported for efficient processing of large datasets.
The input seismic data stream. Connect the output of the preceding processing module in the workflow.
The in-memory seismic gather to be shifted. Each trace in this gather is shifted individually by the amount computed from its corresponding raw header entry in the Raw trace vector.
A collection of raw (binary) SEG-Y trace headers, typically provided by a SEG-Y reading module earlier in the workflow. The module matches each trace in the input gather to its raw header entry by record index to retrieve the byte-position values for the shift calculation. This input is required — if left unconnected, the module will report an error.
A list of raw trace header byte-position fields used to extract the shift values. Each entry defines a byte position in the SEG-Y trace header and its data type (e.g., short integer at bytes 99 and 101 by default). The extracted values are referenced in the mathematical expression as $A$, $B$, etc. in the order they appear in the list. Modify these entries to match the byte layout of the raw headers in your SEG-Y files.
A mathematical formula that combines values extracted from the raw header fields to compute the shift in ms for each trace. The variables $A$, $B$, etc. correspond to the values from the CollectionFields list entries. Standard arithmetic operators are supported. For example, $A$+$B$ sums the two raw header values to obtain the total shift.
Default: $A$+$B$.
Controls the direction of the applied shift. Positive moves trace events to later times (applies the correction). Negative moves trace events to earlier times (reverses a previously applied correction). Use Negative when you need to undo a shift applied in an earlier processing step.
Default: Positive.
When enabled, the module uses linear interpolation to compute output sample values when the shift is a non-integer number of samples, resulting in smoother amplitude representation. When disabled, the module uses nearest-sample (integer) shifting, which is faster but may introduce minor timing errors for sub-sample shifts. Enable interpolation for production-quality static corrections.
Default: Enabled.