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QC Panel Fold is a quality control module that analyzes the trace count (fold) distribution across each offset or azimuth panel in your survey geometry. For each panel — whether defined as an OVT tile, an OVT-2 tile with a separate near-offset tile, or a conventional offset range — the module computes a fold map showing how many traces fall into each bin for that panel, allowing you to verify that the geometry produces uniform coverage before migration.
The module operates in two modes controlled by the Run type parameter: Create output item simply packages the panel configuration (from the Offset table) into an output migration panels item without scanning trace data, while Analyze and create output item reads all trace headers, assigns each trace to a panel, and builds a per-panel fold matrix. The resulting fold matrices and border contours are visualized on a location map and can be passed downstream to pre-stack depth migration workflows.
Interactive visualization lets you click any CDP bin on the fold map to display the corresponding source and receiver positions, and to see the OVT tile grid overlaid at that location. Use this module after geometry application and before running PSDM to confirm that each offset/azimuth panel has adequate and balanced fold throughout the survey area.
The bin grid that defines the survey geometry — inline/crossline layout, bin dimensions, and orientation. This grid provides the fold map template against which panel counts are accumulated. A valid fold map must already exist in the bin grid; if it is missing, recreate the bin grid before running this module.
When set to false (default), the module reads trace geometry from the in-memory Trace headers item. When set to true, it reads header data in bulk from the on-disk trace vector specified by the Input traces data handle. Use the on-disk option for very large surveys where loading the entire trace vector into memory is impractical.
The in-memory trace header collection containing source, receiver, and bin coordinate information for all traces. Used when Use trace vector on disk is set to false. This item is automatically hidden when disk-based reading is enabled.
A handle to the on-disk trace vector storage, used when Use trace vector on disk is true. The module reads trace headers in batches controlled by the Header bulk size parameter. This input is hidden when in-memory trace headers are used.
The number of trace headers to read from disk in each batch when using the on-disk trace vector mode. Default is 1,000,000 traces per batch. Larger values speed up processing but require more memory. Reduce this value if the module runs out of memory on very large surveys.
Selects how the survey is divided into panels for fold analysis. Default is OVT.
OVT — Offset Vector Tile mode. Each panel is defined by a rectangular tile in the 2D offset vector space (inline offset component x crossline offset component). The tile dimensions are set in the Offset tile class group. Use this mode for standard wide-azimuth OVT-PSDM workflows.
OVT-2 — Extended OVT mode with a separate fine-resolution tile for near offsets. Traces are first checked against the Near offset tile class grid; those that do not fit are assigned to the standard Offset tile class grid. This mode is useful when near-offset traces require denser panel subdivision.
Offset — Conventional offset class mode. Each panel covers a uniform range of absolute offsets defined by the Offset class group (from, to, step). Use this for offset-class PSDM or when azimuth information is not needed.
Variable offset classes — Offset class mode with non-uniform panel widths. Offset ranges are defined manually in the Offset classes table, allowing finer sampling at near offsets and coarser sampling at far offsets if desired.
Parameter group defining the OVT tile grid used in OVT and OVT-2 modes. Each tile represents one output panel. The grid covers the 2D offset vector space in the inline and crossline directions.
Minimum inline component of the source-to-bin offset vector included in the tile grid (m). Default is -2000 m. Set a negative value to include tiles on both sides of the CDP bin along the inline direction, or set to 0 when using Absolute tile mode.
Maximum inline component of the source-to-bin offset vector included in the tile grid (m). Default is 2000 m. The total inline span divided by the inline step determines how many panel columns exist in the OVT grid.
Width of each OVT tile in the inline offset direction (m). Default is 800 m. Smaller values produce more panels with finer azimuth and offset resolution but require more traces per panel to achieve adequate fold.
Minimum crossline component of the source-to-bin offset vector included in the tile grid (m). Default is -2000 m. Together with the inline parameters, these four boundaries define the full rectangular extent of the OVT grid.
Maximum crossline component of the source-to-bin offset vector included in the tile grid (m). Default is 2000 m.
Width of each OVT tile in the crossline offset direction (m). Default is 800 m. Should typically match the inline step to produce square tiles; use a different value only if the geometry has strongly asymmetric inline/crossline sampling.
When false (default), the signed offset vector component (source position minus bin position) is used to distinguish tiles on opposite sides of the bin. When true, the absolute value of the offset component is used, folding tiles from opposite sides into the same panel. Enable this option when source-receiver symmetry is assumed and you want to maximize fold per panel.
Parameter group defining a second, finer OVT tile grid applied specifically to near-offset traces. This group is visible only when Panel type is set to OVT-2. Traces that fall within this near-tile grid are assigned to near panels; remaining traces are assigned to the standard OVT grid.
Minimum inline offset component for the near-offset tile grid (m). Default is -200 m. This value defines the inner boundary of the near-offset zone along the inline direction.
Maximum inline offset component for the near-offset tile grid (m). Default is 200 m. Set this to match the actual near-offset extent in your survey geometry.
Tile width in the inline offset direction for the near-offset grid (m). Default is 50 m. This finer step compared to the standard OVT grid provides higher panel resolution in the near-offset zone.
Minimum crossline offset component for the near-offset tile grid (m). Default is -200 m.
Maximum crossline offset component for the near-offset tile grid (m). Default is 200 m.
Tile width in the crossline offset direction for the near-offset grid (m). Default is 50 m.
Same as Absolute tile but applied to the near-offset tile grid. Default is false. Enable to fold near tiles from both sides of the bin into the same near panel.
Parameter group defining uniform offset ranges for Offset panel type. Specify the minimum offset (default 0 m), maximum offset (default 4000 m), and the step size between class boundaries (default 100 m). The module automatically generates the offset table from these values when the Fill offset table by offset or variable offset panels custom action is used.
Starting absolute offset for the uniform offset classification (m). Default is 0 m. Traces with offsets below this value are excluded from all panels.
Maximum absolute offset for the uniform offset classification (m). Default is 4000 m. Traces beyond this offset are not assigned to any panel.
Width of each offset class (m). Default is 100 m. Smaller values produce more panels with finer offset resolution. The total number of panels equals (Offset to - Offset from) / Offset step.
Selects whether fold computation runs on the CPU or GPU. CPU is the default and is supported on all systems. Selecting GPU may accelerate processing on systems with a compatible graphics card.
Options for distributing the computation across multiple nodes in a cluster environment. Leave at default for single-machine processing.
Minimum data chunk size used for distributed or parallel execution. Controls how the workload is split among processing threads or nodes.
When enabled in a distributed execution setup, caps the number of processing threads used on each compute node. This prevents the module from consuming all available CPU resources on shared cluster nodes.
An optional text label appended to the job name when submitting to a cluster scheduler. Use this to distinguish multiple concurrent runs of the same module in the job queue.
When enabled, allows you to pin processing threads to specific CPU cores using the Affinity setting. Leave disabled for automatic thread scheduling by the operating system.
CPU core affinity mask used when Set custom affinity is enabled. Specifies which processor cores the module's threads may run on.
Number of parallel CPU threads used for fold counting. The default uses all available hardware threads. Reduce this value to leave CPU capacity for other concurrent processes.
When enabled, this module is bypassed during batch execution and the input data is passed through unchanged. Use this to temporarily disable the QC step without removing it from the processing sequence.
The module produces one output item: Out migration panels item — a structured object that encapsulates the complete panel configuration (panel type, tile parameters, offset classes) together with the computed per-panel fold matrices and border contour matrices. This item is passed to downstream PSDM migration modules to define the panel sorting and offset/azimuth partitioning used during imaging.
The module provides two interactive visualization views:
Location map — displays the survey area in map view with the overall fold map as a background, per-panel fold matrices and border contour overlays, and the OVT tile grid. Click any location on this map to select the nearest CDP bin; the view then shows the source and receiver positions associated with that bin (for interactive shot geometry inspection), and overlays the OVT tile grid centered at the selected bin.
QC panels graph — a bar/line chart showing the total trace count (summed fold across all bins) for each panel index. Use this graph to quickly identify panels with unexpectedly low fold, which may indicate gaps in the geometry or misconfigured panel boundaries.
Fill offset table by offset or variable offset panels — automatically populates the Offset table from the current Offset class or Offset classes parameters. Use this action after adjusting the offset range and step to regenerate all panel entries without manual editing. Each row in the table receives a panel number, start offset, end offset, and nominal (midpoint) offset value.
Fill offset table by input panels — reads the offset class definitions from a connected input migration panels item and copies them into the Offset table. Use this action to synchronize the panel configuration with an existing panels item from a previous processing step, ensuring consistency between the QC module and the actual migration panels that will be used.