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<< Click to Display Table of Contents >> Navigation: Statics > Import static shifts from files |
This module reads pre-computed static corrections from plain-text (ASCII) files and loads them into gNavigator as a static correction dataset ready for application to seismic traces. Static shifts can be provided separately for sources, receivers, and common midpoints (CMPs), in any combination. The output is passed directly to the Apply Static Shifts module to apply the corrections to trace amplitudes.
Each input file is a whitespace-, tab-, or semicolon-delimited ASCII table. Depending on the selected coordinate type, each row contains either X and Y coordinates followed by the static value, or a line number and shot-point (SP) number followed by the static value. Static values may be in seconds or milliseconds as selected. Lines that do not begin with a numeric character are treated as header comments and are automatically skipped.
Use this module when static corrections have been computed externally (for example, by a refraction statics solver or a land-data processing contractor) and need to be imported into a gNavigator processing flow. You do not need to provide all three files — any combination of source, receiver, and CMP files is accepted.
The loaded geometry (trace header collection), typically produced by a Load SEG-Y or geometry-loading module. This provides the X/Y coordinates and line/SP identifiers of each source, receiver, and CMP in the survey. The module uses these coordinates to match points from the ASCII static files to the corresponding survey geometry positions. Without valid trace headers the module cannot run.
Full path to the ASCII text file containing source static corrections. Each data row must have three columns: the X coordinate (or line number), the Y coordinate (or shot-point number), and the static shift value. Leave this field empty if source statics are not available or not required.
Full path to the ASCII text file containing receiver static corrections. The file format is identical to the sources file: each row contains the position identifier (X/Y or line/SP) followed by the static shift value. Leave this field empty if receiver statics are not available or not required.
Full path to the ASCII text file containing common-midpoint (CMP or bin) static corrections. For 3D data in Line/SP mode, the two identifier columns correspond to inline and crossline numbers. Leave this field empty if CMP statics are not required.
Specifies how positions are identified in the ASCII files. Choose from:
X, Y — The first two columns contain surface coordinates in the project coordinate system. The module matches each file point to the nearest geometry point within the specified Minimum distance, or interpolates to a regular grid if interpolation is enabled. This is the default and most common choice.
Line, SP — The first two columns are the line number and shot-point number. The module looks up each line/SP pair in the loaded geometry to obtain its X/Y position, then applies the same matching or interpolation logic as in the X,Y mode. Use this when the static file was produced by software that identifies points by line and SP rather than by coordinates.
Line, SP, Survey_ID — The file must have four columns: line, SP, survey identifier, and static value. The module performs an exact lookup by all three identifiers. This mode is required for multi-survey datasets where line and SP numbers alone are not unique. When this mode is selected, the Check duplicates option becomes available.
Specifies the unit of the static shift values in the input ASCII files. Select Seconds if values are in seconds, or Milliseconds if values are in milliseconds (the module will divide the values by 1000 before storing them). Default is Seconds. Ensure this matches the actual unit used in your static files to avoid applying corrections 1000 times too large or too small.
The unit of the X and Y coordinate columns in the ASCII files. Select Meters or Feet. When Feet is selected, coordinates are automatically converted to meters to match the project coordinate system. Default is Meters. This parameter is only active when Coordinates type is set to X, Y or Line, SP.
When disabled (default), the module matches each survey geometry point (source, receiver, or CMP) to the nearest point in the static file, provided the distance to that point does not exceed the Minimum distance threshold. When enabled, the static values from the file are first interpolated onto a regular grid defined by Step X and Step Y, and each geometry point is assigned the interpolated value at its location. Use interpolation when the static file coverage is sparse relative to the survey receiver/source density, or when you want to fill gaps in the static map.
The interpolation grid cell size in the X direction, in meters. Default is 100 m. Smaller values produce a finer grid and preserve more spatial detail, but increase computation time. This parameter is only active when Use interpolation is enabled. A geometry point is assigned an interpolated value only if it lies within twice the Step X distance from the nearest file point.
The interpolation grid cell size in the Y direction, in meters. Default is 100 m. Use the same value as Step X for isotropic interpolation. This parameter is only active when Use interpolation is enabled.
The maximum allowed distance (in meters) between a geometry point and the nearest point in the static file for a match to be accepted. Default is 50 m, range 0 to 10 000 m. Geometry points whose nearest file point lies farther than this threshold will not receive a static correction. Increase this value when there is a known coordinate offset between the static file and the loaded geometry (for example, due to small datum shifts), but be aware that very large values may cause incorrect cross-assignment of statics. This parameter is only active when Use interpolation is disabled.
When enabled, the module subtracts the simple elevation static from each imported value before storing it. The elevation static for a given point is calculated as (Datum − elevation) / V replacement. Use this option when the imported static shifts already include the elevation (datum) component and you want to remove it, keeping only the residual component. Default is disabled. When enabled, the Datum and V replacement parameters become active.
The datum elevation, in meters, used for the elevation static subtraction. Default is 0 m. Set this to the reference datum level of the survey (for example, mean sea level or a chosen flat datum). This parameter is only active when Subtract elevation statics is enabled.
The replacement (fill) velocity in m/s used for the elevation static subtraction formula. Default is 2000 m/s. Set this to the constant velocity used to replace the weathering layer in your survey, typically between 1800 and 3000 m/s for land data. This parameter is only active when Subtract elevation statics is enabled.
The primary output: a structured static correction dataset containing the imported shift values assigned to each source, receiver, and/or CMP point. Connect this output to the Apply Static Shifts module to apply the corrections to seismic traces. Only geometry points that were successfully matched to the static file (within the specified distance threshold) receive a correction value.
A secondary output holding the same static values formatted for azimuthal processing workflows. This is used by modules that handle azimuth-dependent statics. For standard isotropic statics workflows, only the primary statics correction item is needed.
After execution, the module generates point-map and grid-map views of the imported and assigned static values for sources, receivers, and bins. These can be reviewed directly in the gNavigator map viewer to verify coverage and check for anomalous values before applying the corrections to the seismic data. The interpolated grid maps (SRC/RCV/BIN statics map import) are only produced when Use interpolation is enabled.