Drillhole Preferences

Use the DH-Data > Preferences menu option (geogxnet.dll(Geosoft.GX.DrillHole.Preferences.DHPreferences;Run)*) to set specified global variables and customize the behaviour of the Drillhole Plotting extension tools.

Any changes made in this dialog will be reflected, as applicable, in the Drillhole Preferences for Evo Import dialog. Conversely, any changes made in the 'Drillhole Preferences for Evo Import' dialog will be reflected here.

Drillhole Preferences dialog options

Import Parameters
Auto-convert negatives on import?	Identify if assay negative values are automatically converted on import. If Yes is selected, all values in the assay channels will be scanned during import. Values less than zero are replaced by positive values that are half their original size (i.e., values are multiplied by –0.5). See the Application Notes below for further details on "negative" assay values and the conversion process. Script Parameter: DHPREFERENCES.CONVERT_NEGATIVES [0: No; 1: Yes]
Survey Parameters
Resurveying method	Resurveying is the mathematical process of converting a series of dip and azimuth measurements taken at various depths down a borehole into (X, Y, Z) coordinates. The collar is assumed to be at zero depth, and depth is the measured distance down the hole (even if it's horizontal). Select one of the available methods: Radius of curvature: The original resurveying method used in previous versions of Oasis montaj/Target. It synthesizes the trace as a collection of circular segments, each starting and ending at a single (dip, azimuth, depth) location. Polynomial fit: This method models the traces as a polynomial of a specified order that best fits the set of (dip, azimuth, depth) values. Higher orders provide better fits, with a trade-off in the overall smoothness of the hole trace. Straight segments: This method creates straight line segments between each survey depth reading, with no interpolation. It is primarily used for trenches or near-vertical holes. The (X, Y, Z) coordinates are stored in the 'DH_East', 'DH_North', and 'DH_RL' channels in the drillhole databases. For interval ('From-To') databases, these channels are calculated from the collar and survey data using the selected resurveying method and represent the midpoint of an interval. Script Parameter: DHPREFERENCES.RESURVEY [0: Radius of curvature; 1: Polynomial fit; 2: Straight segments]
Order for polynomial fit	This parameter is used in the polynomial fit resurveying method described above. The polynomial order is limited by the number of (dip, azimuth, depth) values, with a maximum of 20. A value of 5 is adequate for most smoothly curving holes. A higher order results in more accurate matching of dip and azimuth at each surveyed hole depth, while a lower order produces smoother final hole traces. Script Parameter: DHPREFERENCES.POLY_ORDER
Hole survey dip angle sign (downward)	Identify if the hole survey dips are negative downward or positive downward: Negative : Negative survey dips indicate holes pointing downward. Positive: Positive survey dips indicate holes pointing downward. Oasis montaj/Target has traditionally used the convention that dip is negative downward, meaning vertically downward is –90.0 degrees. Typically, vertically downward is +90 degrees, and selecting the 'positive' setting will cause Oasis montaj/Target to interpret all dip values in a drillhole database accordingly. This simplifies the import of data from other packages or formats where dips are positive downward. This convention is applied at plotting time, so if all your holes appear to go “up” instead of “down”, change this setting to correct the orientation. Script Parameter: DHPREFERENCES.DIP_SIGN [-1: Negative; 1: Positive]
Azimuth magnetic declination correction	Specify the magnetic declination correction angle to be applied to the X, Y, Z coordinates ('DH_East', 'DH_North', 'DH_RL' channels) for the survey, interval, and depth databases. Many down-hole surveys use a Kodak-Eastman survey device, which records the azimuth in relation to a magnetic compass bearing. Consequently, the azimuth values recorded in the collar table and dip-azimuth survey databases do not reflect the "true" azimuth measured relative to north. This correction value will be added to the survey, interval, and depth data before resurveying. For instance, if magnetic north is 10 degrees west of true north, and the stored azimuth values are relative to magnetic north, enter the value "-10" as the correction. An azimuth of 10 degrees west will then be corrected to 0 degrees (true north) before resurveying the hole. Essentially, holes are rotated around the collar position by the correction angle. Script Parameter: DHPREFERENCES.AZIMUTHCOR
Plotting Parameters
Default mask channel	If a mask channel is specified, it will appear as the default mask channel in any GX where the mask channel selection has not yet been made. The mask channel will have its Class type set to MASK. Only data values where the corresponding mask value is not a dummy, "", will be used for plotting or exporting data. When plotting, masked-out points or intervals will not appear, nor will depth ticks for these values. If no mask channel is specified, no masking occurs, even if the Use mask channel for plotting/export* option is set to "Yes". Although logically a "NO", '0' is treated as a non-dummy, so the data remains selected. Only the dummy "*" can be used to mask out data. Values can be set to dummy by selecting them in the database and pressing the space bar. Script Parameter: DHPREFERENCES.MASK
Map template	Select a standard template to define the map layout. The map layout includes media size, map margins, and page orientation. Script Parameter: DHPREFERENCES.TEMPLATE
Rock codes list file (*.csv)	Two rock codes data files (AGSO.csv and rockcode.csv) are provided and can be found in the %USERPROFILE%\Documents\Geosoft\Desktop Applications \csv folder. You can specify one of these files or your own standard rock codes list file (in CSV format). If you generate your own CSV files, store them in the %USERPROFILE%\Documents\Geosoft\Desktop Applications \csv folder. Script Parameter: DHPREFERENCES.ROCK_CODES
Structure codes list file (*.csv)	Specify a structure code list file. Structure codes and their associated colours are typically used with point (single-depth) data to colour structure symbols such as structural ticks, tadpole plots, and symbols in Stereonet plots. Script Parameter: DHPREFERENCES.STRUCTURE_CODES
Hole discretization interval	The resurveying process calculates the hole location at intervals specified by this parameter. This interval affects the accuracy of intersection and cut-off points, such as when a hole exits or enters the current view "slice". It also affects the averaging functions used when plotting graphs of data down the holes. Script Parameter: DHPREFERENCES.DISC_INTERVAL
Right/left for posted data	Use the drop-down list to select the method for posting data on a map. Two methods are currently available: Hole reference: The side on which data is plotted is determined with reference to the direction of the hole. If you orient the map so that the collar is "up" and the hole runs down, then left and right are as viewed at that time. Map reference: The plotting side is adjusted based on the orientation of the hole on the current map. This adjustment is made with reference to the collar orientation and can lead to somewhat unpredictable results when a hole plots nearly horizontally on a map. Script Parameter: DHPREFERENCES.LEFTRIGHT [0: Map reference; 1: Hole reference]
N-S Sections face….	Use the drop-down list to select the direction N-S sections face: By default, N-S sections are defined with an azimuth of 0 degrees, facing West. This means South is to the left and North is to the right, with the northing value increasing from left to right. Traditionally, N-S sections have been defined with an azimuth of 180 degrees, facing East. In this case, North is to the left, South is to the right, and the northing value decreases from left to right. Script Parameter: DHPREFERENCES.EASTWEST [0: East; 1: West]
Use mask channel for plotting/export?	If a default mask channel is specified, you can enable its use. Choose Yes to create a mask channel (within the collar, interval, and depth databases) allowing you to select and deselect individual data points when plotting or exporting data. The initial values in the mask channel are set to 1, so all points are automatically selected upon data import. Prior to version 5.1.3, these values were initialized to dummy "*", so they must be manually reset to 1 for your data to be selected once you enable the mask channel. Failure to set any values to 1 may result in errors, such as the inability to determine the range of selected data (since no data is selected). Script Parameter: DHPREFERENCES.USEMASK [0: No; 1: Yes]
Angled section axis origin	When creating grids for E-W or N-S sections, the section’s X axis aligns with the Easting and Northing, respectively. For an angled section, however, there is no absolute reference. The view origin is important to know if you wish to import gridded data (for instance) into the view, as the grid’s X-axis origin will plot on the section view’s X-axis origin. To correctly center the grid, it may be necessary to alter the grid’s X-axis origin location to correspond to the section’s X-axis origin. The angled section view’s X axis origin can be set to one of the following choices: Center: By default, the X=0 location of the section is at the center of the grid. The center is chosen as default because it corresponds to the (Easting, Northing) location specified in the section location, making it simpler to calculate the true location of all points on the section. Left edge (start of section): In some situations, you may have grids where the grid X=0 location corresponds to the left side of the plotted section. Select this option to correctly locate these grids without needing to alter the grid origin. Script Parameter: DHPREFERENCES.ANGLEDSECX0 [0: Center; 1: Left edge]

Application Notes

*The GX.NET tools are embedded in the geogxnet.dll file located in the "...\Geosoft\Desktop Applications \bin" folder. If running this GX interactively, bypassing the menu, first change the folder to point to the "bin" directory, then supply the GX.NET tool in the specified format. See the topic Run GX for more details on running a GX.NET interactively.

Global Variables

Drillhole Preferences are global variables that remain set for a given installation of Oasis montaj/Target. The values are stored in the geosettings file located in the user-specific directory '%USERPROFILE%\Documents\Geosoft\Desktop Applications\ini'. This ensures they remain consistent across different data sets and Oasis montaj/Target projects, and the settings are applied to any relevant processes (GXs) within the extension's workflows.

"Negative" Assays

Assay values represent the measured geochemical concentrations of elemental abundance in geological samples (such as rock, soil, water, drill core, or rock samples). When assay values are measured in the lab, the concentration of an element can sometimes be very small, making it too low to be accurately detected by the method that is used to measure the concentration. This results in assay measurements reported using a "lower detection limit" value, often shown as a negative value or with a less than ('<') sign, such as '-0.01'. On import, you can choose to automatically convert these negative values or '<' signs to a value that is 1/2 of the numeric value used.

Resurveying Drillholes using Collar and Survey Data

The drillholes are always "resurveyed" on import, which means a 3D spatial object (a drillhole "trace") is calculated for each drillhole. The output trace for any given hole can vary depending on what type of data is available during import (e.g., collars only, collar and survey data, etc.) and which method is selected to do the resurvey calculations. The various ways to calculate the traces, depending on which types of data are available, are described below:

With collar locations only, no survey data present:

If collar data includes dip and azimuth, these values are used to create straight segment traces for the entire hole, to the final depth.
If collar data does not include dip and azimuth, the holes are assumed to be vertical.

With collar locations and dip-azimuth survey data:

The survey data is "discretized" at the resurvey resolution interval value and a smooth curve is generated using the selected resurveying method.
The top-of-hole dip and azimuth values (at depth = 0) will use the values from the survey data, if present.
- Individual drillholes lacking survey data will be assigned default values: a dip of 90° and an azimuth of 0°.
- Drillholes that do not have a 0 start to their survey data will have the collar dip and azimuth values set to default values (90° and 0°, respectively) to ensure the X, Y, Z coordinates of intervals/depths are in the correct location.

A "resurvey" is triggered also when the Refresh tools are used. If any manual edits were made to collar location or survey measurement values (e.g., for incorrect X, Y, Z collar location or Dip/Azimuth/Depth survey values), a "resurvey" needs to be performed in order to recalculate the X, Y, Z collar and dip/depth/azimuth survey data.