General Module Function
Krig Fence models parameter distributions within domains defined by the boundaries of the input data in 3D Fence sections which can "snake" around in the x-y plane and are parallel to the z-axis. Krig_Fence can also receive the geologic system modeled by Fence Geology. It creates a quadrilateral finite-element grid with kriged nodal values of any scalar property and its kriged confidence level, and outputs a geometry whose elements can be rendered to view the color scaled parameter distribution on the element surfaces. Krig Fence provides several convenient options for pre- and post-processing the input parameter values, and allows the user to consider anisotropy in the medium containing the property.
Module Input Ports
Read_CSV_data_file (Yellow/Blue/Yellow): This port is the filename (see above).
fld_in (Brown/Grey/Green): This port can only accept output only from Fence Geology.
external_data (Blue/Black): This port allows external data to be imported and kriged to the created fence grid.
Module Output Ports
Read_CSV_data_file (Yellow/Blue/Yellow): This port is the filename.
ucd_out (Blue/Black): This port outputs a data field for a cross section, which can be input to the Fence Merge module. The Fence Merge module accepts data fields from multiple Krig Fence modules, and merges them to produce a fence diagram.
out1 (Blue/Black): This port outputs a typical data field which can be input to external faces (and/or any of the Subsetting and Processing modules which have the same color port) to produce a geometry of a single cross section.
Selecting Semivariogram Parameters in the Kriging Pramaters window, and then selecting Plot Semivariogram will cause an additional three ports to appear as shown below.
out2 (Red/Grey): This port can be connected to the viewer, and will output a renderable geometry of the calculated semivariogram.
VG_fld_out (Blue/Black): This port will output a field consisting of the 3D lines that make up the variogram, this is generally passed to the Generate Axes module.
VG_scale_fact (Grey/Brown): This port will output the variogram scale. This is also generally used in the Generate Axes module.
Module Status: Interruptible
This module's computational processes can be terminated (interrupted) using the "C Tech" icon in the Windows Notification Area (aka System Tray) in the lower right corner of your desktop. If you hover over the icon, it will tell you the status of the module and expected completion time. Double-Right-Clicking will terminate the process. Note that if you do stop any process, the output of the module is corrupted and any downstream module's results are not usable. You will need to re-run the module.
Module Control Panel
The control panel of Krig Fence is shown in the figure above. The Read Data File button opens a File Browser as described for Krig_3D_Geology, but which lists the *.csv, *.gwc, and *.vdf files that are present in the current directory shown in the directory window. The format of .csv files is described in the csv file format help topic.
One instance of Krig Fence reading one .csv file is required for each cross section that will be included in the fence diagram. The data for borings at which the fences will intersect are included in each of the intersecting cross section files
The Data Component slider allows the user to select which of the property values in the .csv file will be kriged by execution of the module. The default value is 0, which corresponds to the first property included in the .csv file.
Krig Fence will not begin running until a valid file has been selected and the Accept All Current Values button is pushed.
Module Parameter Subpanels
Krig Fence has four subpanels, which allow the user to set the parameters used for processing the input data, producing the semivariogram, and executing kriging. Clicking on either the check boxes next to the subpanel names, or on the names themselves, will bring up the subpanel parameter screens. Note that the subpanels can be closed only by clicking on the box in the Module Control Panel, and not by double clicking on the subpanel's window control icon (the small horizontal bar in the upper left corner of the window).
The Gridding Options subpanel is shown in the figure above. It is used to specify all parameters that affect the grid exported from Krig_Fence. The availability of many options depends on whether geologic input is available or if the grid is created totally within Krig_Fence. The window above shows the options with no geologic input.
The Minimum X, Maximum X, Minimum Y, Maximum Y, Minimum Z and Maximum Z parameters allow the user to define the horizontal and vertical domain within the data set in which kriging of the parameter distribution will be completed. A value of 0 is the default for these parameters, which results in a model domain that is defined by the rectilinear bounds of the entire data set when the module is run. Krig_Fence utilizes a model domain that is bounded by the limits of the data set, unless the user specifies a different domain by setting the Min and Max Values for X, Y, and Z, or it is passed a model (or finite-difference) domain from Fence_Geology. Utilizing the default extents effectively minimizes the extrapolation of parameters within the model to that area which is enclosed by the measured data points. Note that when a geologic model domain is passed to Krig_Fence, the kriging domain is restricted to that domain regardless of what X, Y, or Z values are set in the Krig_Fence inputs. If the user is uncertain of the X, Y and Z limits of the data domain, the module should be run with the default 0 values, and upon completion of execution, the values in the X, Y, and Z input fields will be the min and max values of these parameters in the data set. The Stat CSV GEO module can also be used to investigate the limits and distribution of values in the input data set, and the statistics module can be used to output the distribution of values in the kriged model.
The X & Y / Z Resolution parameters specify the number of grid nodes that will be included within the model domain. The number of grid elements along any axis of the model is simply the axis Res value minus one, as every element has two bounding nodes along an axis. The default value for the X and Y Res parameters is 51, and the default value for the Z Res is 35. However, the user can specify any number desired, up to the limit of available memory resources in the computer and run time limitations imposed by the patience of the user.
If geologic layers are being passed to Krig_Fence, then the number of nodes specified in Z Res will be distributed over the geologic layers in a manner that is approximately proportional to the fractional thickness of each layer relative to the total thickness of the geologic domain.
NOTE: If Proportional Gridding is toggled off then only Min Cells per Layer is enabled. In this case, only the Min Cells per Layer input will be used for each layer of the model.
Proportional Gridding - A toggle for activating the same algorithm for apportioning nodes in the Z direction as used in Krig_3D. The number of nodes specified for the Z Resolution will be distributed (proportionately) over the geologic layers in a manner that is approximately proportional to the fractional thickness of each layer relative to the total thickness of the geologic domain. In this case, at least three layers of nodes (2 layers of elements) of the Krig_3D domain will be placed in each geologic layer.
Min Cells per layer - A Type in for establishing a minimum number of cells (in the Z direction) per layer. The default is 2 cells which results in 3 nodes.
Reverse Surface Hierarchy – This toggle determines whether the surfaces will define layers in a normal (top to bottom) manner or reversed (if on). This topic is discussed in more detail in Workbook 12.
The Rectilinear Offset parameter is used to create an automatically generated rectilinear domain which is larger than the input data set by a user input percentage along all three axes. If 10% (0.1 default value) is used, the limits will be offset by 5% on all 6 sides of the rectilinear volume.
The Data Preprocessing parameters subpanel is shown in the figure above. It is divided into two groups which are preprocessing and postprocessing.
It is important to note that all preprocessing actions are applied directly to the data in memory, and that the original data file is not altered. However, all of the functions within Krig_Fence and the modules downstream of Krig_Fence will be using the preprocessed (and kriged) parameter distribution. The user should refer back to the preprocessing subpanel when setting values for the filtering and display of the kriged data (i.e., to correctly specify whether the data has been log transformed, scaled, and/or clipped).
The Data Processing radio buttons allow the user to specify whether the data will be used as is, or will be processed to compute the log (base 10) of the parameter value before kriging. Note that if the log10 of the data is taken, a Clip Min value (which must be greater than 0) must be used to replace values in the data below the specified minimum value because the log function is undefined for values equal or less than zero.
The Data Scaling input field is used to specify a value by which all nodal data values will be multiplied before kriging. The default value is 1, but the user can specify any negative or positive value. This option is most commonly used to convert the units of the property being kriged, such as to convert concentrations in ppb to ppm or visa-versa. The user should bear in mind that any scaling of the data that is completed in Krig_Fence will affect all downstream modules.
The number entered into the Pre-Clip Min input field will be used during preprocessing to replace any nodal property value that is less than the specified number. When log processing is being used, the value of Clip Min must be a positive, non-zero value. Generally, Clip Min should be set to a value that is one-half to one-tenth of the lowest detection limit in the data set, unless the user wishes to make the influence of not detected values stronger. As an example, if the lowest detection limit is 0.1 (which is present in the data set as a 0), and the user sets Clip Min to 0.0001, the clipped non-detected values forces three orders of magnitude to be present between any detected value and the non-detected values.
The number entered into the Pre-Clip Max input field will be used during preprocessing to replace any nodal property value that is greater than the specified number. The clipping values can be used to lessen the importance placed on extremes of the data, or outlier data values, before kriging. The preprocessing functions can be used in various ways to investigate the kriging confidence levels within specified ranges or limits of the data sets. An example of this type of analysis is provided in the Sample Networks section.
The LT Multiplier value affects any file value with a preceeding "<" character. It will multiply these values by the set value.
The Detection Limit value affects any file values set with the "ND" or other non-detect flags (for a list of these flags open the help for the CSV file format). When the module encounters this flag in the file it will insert the a value equal to (Detection Limit * LT Multiplier).
Postprocessing of the data from Krig_Fence affects the calculation of the kriging confidence and uncertainty estimates that are produced by the model, and allows the user to apply a filter for the data passed to all modules downstream of Krig_Fence. Note that the postprocessing does not affect any of the other Semivariogram or kriging algorithms that execute in Krig_Fence, so the user can experiment with different values of postprocessing parameters to obtain the type of display desired, independent of the internal kriging process.
The Post-Clip Min parameter specifies the smallest nodal value that will be present in the data field output by Krig_Fence. This parameter is useful for limiting or enhancing the effects of not detected values or outliers in a data set, and for optimizing the use of the dynamic color range used to represent the property distribution. Clip Min has a default value of 0.001, but can be set to any negative or positive value with magnitude from -1.0 E09 to 1.0 E09. In general, good results are obtained by setting this value to the lowest property value or detection limit in the input data set. It is important to note that because not detected values are represented in the .csv file as zeros, the Clip Min value can be used to strengthen the influence of small values or non detects that are present in the data set. As an example, if the detection limit for a certain chemical analysis is 0.1 (which is entered into the .csv file as 0), and the Clip Min is set to 0.0001, then this not detected value will have an effective influence on the kriged distribution near this data point that is three orders of magnitude stronger than the actual detection limit. The user should bear in mind that if mass or volume estimates are being made in the analysis, the Clip Min value could affect the estimates if considerable data are present that are being clipped. For volume estimates, if the specified lower bound of the concentrations of interest is well above the Clip Min value, then their will be no effects on the results. If the specified lower bound of concentrations for the volume estimate is lower than Clip Min, then the clipping will truncate the volume at the Clip Min value, and the estimated volume will be from the entire model domain.
The Post-Clip Max parameter specifies the largest nodal value that will be present in the data field output by Krig_Fence. Again this parameter can be used to optimize the use of the dynamic color range when a data set has a few extremely high values, but the user is most interested in seeing the detailed changes in the distribution in some lower range of the data. It can also be used to investigate the kriging confidence or uncertainty levels near certain threshold values of a property. As an example, if the regulatory threshold for a parameter is 10 units, then the Clip Max parameter can be set to 10, and all kriged values greater than 10 will have the same strength in the calculation of the uncertainty levels in the kriged distribution. Clip Max has a default value of 1,000,000, but can be set to any negative or positive value with magnitude form -1.00E09 to 1.00E09.
When external data is being imported into the module the External Data to Krig window becomes active. This window allows the user to select which data components to krige by switching on or off the toggles associated with that data component. The Automatically exponentiate log data toggle will detect if the data being imported has been log processed and if it has exponentiate it. This avoids double log processing the data with the Preprocessing option.
The Krig_Fence Time Options window is the same as that of Krig_3D
The Krig_Fence Kriging Parameters window is the same as that of Krig_3D
Further explanations of the use of Krig Fence are presented in Workbook5 .