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Calculate GridParams analyses the trace header geometry of a seismic dataset and automatically derives the fundamental grid parameters of the survey. Given a set of trace headers containing inline and crossline numbers and surface coordinates, the module computes the total count of inlines and crosslines, the first and last line numbers in each direction, the physical spacing between lines, the total extent of the survey along each direction, the surface coordinates of the grid corners, the azimuth of the inline direction, and the angle between the inline and crossline axes.
This module is typically used as a diagnostic or geometry-verification step after binning, to confirm that the survey grid is regular and that line numbers, spacings, and orientations are consistent with the acquisition design. All results are written as output parameters that can be inspected or passed to downstream processing steps. Note that this module is deprecated — newer binning and geometry modules provide equivalent functionality with additional capabilities.
The set of trace headers for the seismic dataset whose grid parameters are to be calculated. The headers must contain valid inline numbers, crossline numbers, and surface X/Y coordinates for every trace. The module reads these header values to derive the complete geometry of the survey grid without needing access to the actual seismic amplitude data.
All values below are computed automatically from the input trace headers. They are read-only results — there are no user-settable parameters for this module.
The total number of distinct inline numbers found in the trace headers. This gives the extent of the 3D grid in the inline direction. If this value is unexpectedly small or large, the inline header word assignment should be checked in the geometry setup.
The total number of distinct crossline numbers found in the trace headers. This gives the extent of the 3D grid in the crossline direction.
The smallest inline number present in the dataset. Together with the last inline number and the inline count, this defines the inline axis of the survey grid.
The largest inline number present in the dataset.
The smallest crossline number present in the dataset. Together with the last crossline number and crossline count, this defines the crossline axis of the survey grid.
The largest crossline number present in the dataset.
The physical distance (in metres) between adjacent inline lines, measured perpendicular to the inline direction. This corresponds to the crossline sampling interval on the ground surface. A value consistent with the nominal receiver line spacing confirms correct geometry.
The physical distance (in metres) between adjacent crossline positions, measured along the inline direction. This corresponds to the bin size in the inline direction on the ground surface.
The total physical length (in metres) of the survey along the inline direction — that is, the distance spanned from the first to the last crossline position measured along an inline. This represents the lateral extent of the 3D volume in the inline direction.
The total physical length (in metres) of the survey along the crossline direction — the distance spanned from the first to the last inline position measured along a crossline. This represents the lateral extent of the 3D volume in the crossline direction.
The surface X and Y coordinates of the point corresponding to the first inline number in the dataset. These coordinates are taken directly from the trace headers and define one corner of the survey grid. They are reported in the same coordinate system as the input geometry (typically metres in a projected coordinate reference system).
The surface X and Y coordinates of the point corresponding to the last inline number in the dataset. Together with the first inline coordinates, these define the orientation and length of the inline axis on the ground surface.
The surface X and Y coordinates of the point corresponding to the first crossline number in the dataset. These define one end of the crossline axis on the ground surface.
The surface X and Y coordinates of the point corresponding to the last crossline number in the dataset. Together with the first crossline coordinates, these define the orientation and length of the crossline axis on the ground surface.
The geographic azimuth of the inline direction, measured in degrees clockwise from North. This describes the orientation of the survey grid relative to true north. A value close to the acquisition design azimuth confirms that the geometry is correctly loaded.
The angle (in degrees) between the crossline and inline axes of the survey grid. For a perfectly orthogonal 3D survey this value should be 90 degrees. Deviations from 90 degrees indicate a non-orthogonal grid, which may be the result of irregular acquisition geometry or an error in the geometry assignment.
This module has no user-configurable parameters. All processing is driven entirely by the content of the input trace headers.