Geosoft - Exploring With Data

Displaying Drillhole Data More Effectively in 3D

For my first Roundup-inspired post, I picked a topic that every explorer I meet is interested in – working more effectively in 3D.

Displaying drill holes in 3D using DH-Plot > 3D Map is a convenient way to create a 3D map, complete with a legend, showing selected holes, topography, and two types of data.  Here, as may often be done in a 2D section, lithology has been plotted as a Rock pattern and gold assays are displayed as a Bar plot.  It is easy for this to become cluttered, making it hard to see significant characteristics in your data.

In order to start from a cleaner, less cluttered view of your data, try this instead:

1. Use DH-Plot > 3D Map to create the 3D map of the selected holes in the drillhole project, but leave the Data tab blank. For an even cleaner starting point, try turning off Plot Depth Ticks.

2. In the 3D Viewer, select the Add to 3D > Drillholes menu option.  Instead of plotting the geology as a Rock pattern, display only important geological intervals using discrete values in a Text band.

Discrete intervals in the Number bands option is also a good way to display significant ranges from assay results.

3. In order to display other discrete intervals from the same channel using the Add to 3D > Drillholes menu option, first rename the existing group.  Then you can toggle this layer on and off as you build your 3D data groups.

Now use the Add to 3D > Drillholes menu option to add more geology intervals or other downhole data.

4. Finally, add the Topography grid to help orient your 3D view relative to the surface.

Direct Gridding

New in Oasis montaj 7.3 and Target 7.3, and a fast and useful gridding algorithm: Direct Gridding.

Direct Gridding can be used to create a grid from highly sampled data without using any interpolation.  You can use the minumum, maximum, or mean value in the cell.  It is also a great way to make a grid from regularly sampled data. I used this to grid global topography from a large XYZ file.

Replot Holes on Existing Plan or Section

One of my colleagues recently told me that she talks to a number of Target and Drillhole users who are not aware of, or have forgotten about, a really useful option to "Replot Holes on Existing Plan or Section".

The Replot Holes option has fewer parameters than the standard Plan and Section tools.  It only updates the drillhole groups and does not overwrite or create a new map. This makes it useful for tasks such as adding proposed holes that were added to the project or updating the data being plotted along the trace when new logs or lab results are ready.

3D View Orientation Buttons

New in 7.3 - quick 3D view orientation buttons in the 3D Viewer

Use these buttons to quickly view the 3D model from a cardinal direction, above or below, OR set your own inclination and declination viewing angle.

Reprojecting database coordinates with a script

Today I came across a Geosoft Knowledge Base article called How to reproject the X,Y coordinates in a database.  This is a handy little reference, as I used to do this task (or show others how to do this) on a regular basis. 

On one project, I set up a little script to do it for me. It was simple to create (learn more about scripting in this video!), saved time, and prevented the possibility of making small but costly errors if I were to do it manually each day.

What's New 2011 - 3D clipping

The Geosoft 2011 Update is now available. Look forward to a few new articles here about some of our favourite new features and functions.

Today's tip: In Oasis montaj, Target, and Extensions for ArcGIS, you can now use the 3D view clipping tools to clip all 3D object types, including: drillholes, symbols, grids and surfaces. You can also select and clip multiple groups at once.

How do I use the Mask channel in a drillhole project?

When you import your data into a Target project, you will notice that all of the output Geosoft databases (*.gdb files), except for the survey database have a Mask channel.

A Mask channel generally holds binary data and is usually of data type byte.  Mask channels will either contain the value (usually 1) or dummy (*).  The Class for mask channels is indicated by MASK in the Edit Channel dialog.

 

If a row is populated with the value 1 for the Mask channel, that data is not being masked.  When the row has a * in the mask, it is only masked if the user selects the mask option.

 

Collar database

The Mask channel in the collar database works differently than the Mask channel in other drillhole databases. In drillhole projects, the Mask channel in the collar database indicates which holes are selected. Selected holes will have a value of 1 for the Mask channel and unselected holes will have a dummy (*). There are several different ways to select and unselect drillholes.  These options are found under:

Target Standalone (and Oasis montaj with Drillhole Plotting extension)

• DH-Data menu > Select Holes

Target for ArcGIS

• Target Drillhole toolbar > Selection (first 7 options)

Only drillholes that are selected will be included in output plots.  Additionally, processing like 3D gridding and Channel Math will only be performed on selected holes.

 

From-to or Point Databases

The Mask channel in from-to or point drillhole databases works differently than the mask channel in the collar database.  In these types of databases, the Mask channel can be used to mask data that is being plotted.  You first have to indicate that you want to use the Mask channel for plotting/export.  This is done through:

Target Standalone (and Oasis montaj with Drillhole Plotting extension)

• DH-Data menu > Preferences > Use mask channel for plotting/export? 

Target for ArcGIS

• Target Drillhole toolbar > Target Project > Preferences > Use mask channel for plotting/export?

If this parameter is set to Yes, you can mask data that is displayed in plots.  For example, the below plan map was created showing a single drillhole trace and the rock patterns along the trace.  No data is being masked in the geology from-to database.

You can adjust the values in the Mask channel for all the holes in the project using some of the other selection tools.  Let’s say that you only want to plot the rock types “Ca” and “Sif” on your output map.

Target Standalone (and Oasis montaj with Drillhole Plotting extension)

• Make the Geology database the active table.
• DH-Plot > Select Data by Code.
• Select the appropriate channel and other parameters in the dialog > OK.
• The Select Codes dialog will open and you can select the codes of interest.

Target for ArcGIS

• Make the Geology database the active table.
• Target Drillhole toolbar > Selections > Select Data by Code.
• Select the appropriate channel and other parameters in the dialog > OK.
• The Select Codes dialog will open and you can select the codes of interest.

Result of the “Select Data by Code” in the database...

Now if the plan map is recreated, it looks like this...

Other selection tools that can be used for from-to and point databases are:

• Select Data From Map (only in Target or Oasis montaj)
• Select Data by Range

The Mask Channel can quickly be reset to all 1’s or dummies:

• Reset Mask Channel

3D vectors for contours created from a grid

Recently, some of us here at collaborated on a workflow to export topography contours to a 3D vector format.  We thought it'd be a useful one to share with our customers.  Here's how you go about it.

When creating the contours for the grid, modify the Options:

• Set the suppression density to 0 mm.
  This will ensure that the contour lines are closed.  
• For "hi-low annotation", select none.
• For label display, select no labels.
• Optionally define smoothing for the contours

Oasis montaj and Target

In Oasis montaj and Target, the contour option is found under Map Tools > Contour > Contour.  Once the contours are added to the map, select the contour group in the View/Group Manager Tool and export the selection to a 3D Shapefile through Map > Export > ArcView Shapefile.

MapInfo users can export the contour group to a TAB file and the Z value will be the value of the contour level.

Extensions for ArcGIS

In Target for ArcGIS, the contour option is found on the Target Surface toolbar. In Geochemistry for ArcGIS, the contour option is found in the Gridding menu.  Both Target for ArcGIS and Geochemistry for ArcGIS allow you to create the contours directly in Shapefile format.

Geosoft 3D Viewer and 3D DXF export

The 3D Shapefile can be added to the Geosoft 3D Viewer (Add to 3D menu > Imports).  The 3D Shapefile displayed in the 3D Viewer can be exported to a 3D DXF (Export menu > AutoCAD DXF File).

Recreating plots and replotting holes in Target

Recreate plot

Often you'll find it is necessary to recreate a plan map, section map or strip log with only a few changes to the parameters that were used to create the map.  This can be difficult to do from the menu options if the settings in the multi-tabbed dialogs have been changed while creating other maps.  However, the original settings used to create a map can be accessed and used to recreate the map, or create a new updated map.  Here’s how:

1. Select the collar database as the active table to ensure the map is linked to the drillhole project.
2. Make your map of interest the active window.
3. Select the Holes group in the View/Group Manager Tool.
4. Right-click on the map > select Recreate Plan (or Section, Strip Log).
   The Plan Map Parameters dialog will open with the parameters that were used to create that map.
5. You can adjust any of the parameters.
   If you do not want to overwrite the existing map, make sure you add a "Map Name Tag" on the Page Layout tab.
6. Click OK to recreate the map.

Replot holes

For Plan and Section maps, you can use the "Replot Holes" function from the DH-Plot menu to update the map.  This is similar to the above tip but the replot dialog has fewer parameters that can be changed for the active map because it only updates the groups and does not create a new map.

For example, this function could be used to plot proposed holes that were added to the project or to change the data being plotted along the trace.  

Data Quality using Profiles

When I receive a new point or line-based dataset, often my first action is to use Oasis montaj or Target to look at the channel profiles in a Geosoft database (after importing the data into a Geosoft database, if required).  This is a valuable way to check the data quality and get familiar with the data.

Profiles of the coordinate channels (x,y) help to quickly identify location errors from missing values, reversed x and y coordinates, or simple typos.  Line data coordinates usually have smooth and consistently increasing (or decreasing) profiles.

 

Profiles of the data can be used to look for strange values and noise. Selecting any suspicious locations in the profile window will jump to that location in the database table.

 

I often select the line header cell and use the Page Up and Page Down keys to scroll between adjacent lines in the database for a quick way to review the data.

If this data format is being collected regularly, then saving the database view (Database > Save Working View...) makes the review of data channels more efficient next time.