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<< Click to Display Table of Contents >> Navigation: Geometry > GVelocityHeadersCreator |
Note: This module is deprecated and retained for backward compatibility only. It is not recommended for use in new processing flows.
GVelocityHeadersCreator updates the trace header geometry fields of a velocity gather. It recalculates the inline picket spacing (delta-X) from the actual bin positions of the input traces and rescales the depth sampling interval into milliseconds. Optionally, it can estimate the surface topography for each bin location using a user-supplied constant velocity and write those elevation values into the bin, source, and receiver coordinate headers.
This module belongs to the Geometry processing group. It is intended for preprocessing velocity gathers before depth imaging workflows where correct spatial and elevation header information is required. The topography estimation option is useful when a smooth near-surface model is needed but no independent elevation survey data are available.
The input velocity gather to be processed. This gather must have a non-empty set of binned traces; if the bin set is empty the module will report an error and stop. Connect this input to a velocity gather that has already been binned so that each trace carries a valid bin picket coordinate.
This parameter group controls whether the module estimates and writes surface topography into the trace headers. The topography is derived by finding, for each bin column, the first depth sample whose velocity differs from the user-specified constant topography velocity. That depth position is then smoothed and written as the elevation (z-coordinate) of the bin, source, and receiver header fields. All three parameters below work together and are only active when topography writing is enabled.
Enable this option to compute and write estimated surface elevations into the bin, source, and receiver coordinate headers of each trace. When disabled (the default), the module only updates the picket spacing and depth-to-time scaling of the gather and leaves elevation headers unchanged. Enable this option when downstream depth imaging or static correction steps require elevation information that is not already present in the headers.
Default: disabled (false).
The constant velocity (in m/s) used to identify the surface of the earth within the velocity gather. The module scans each bin column from the top and marks the first depth sample whose velocity differs from this value as the ground surface. This defines the topographic elevation written to the headers. Set this value to the near-surface replacement velocity or water velocity that fills the shallowest part of your velocity model above the real geology. The value must be greater than 1 m/s; entering a value of 1 or less will produce an error.
Default: -1 m/s (invalid; must be set to a positive value before enabling topography writing).
Controls how much lateral smoothing is applied to the estimated topography profile before it is written to the headers. A value of 0 writes the raw, un-smoothed topography picks directly. Larger values apply progressively stronger smoothing along the inline direction, suppressing sharp lateral variations in the derived elevation. Use higher values to produce a smooth datum suitable for static corrections; use 0 or a small value when the raw velocity-derived picks are already well-behaved or when you want to preserve sharp topographic features.
Default: 10.
The processed velocity gather with updated trace header geometry. The inline picket spacing (delta-X) has been recalculated from the actual bin positions, and the depth sampling interval has been converted to milliseconds. If topography writing was enabled, the bin, source, and receiver elevation header fields also reflect the smoothed topography derived from the constant-velocity model.