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.

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).

Can I Delete That File?

Geosoft stores all kinds of information in files and datasets (a dataset is a collection of related files). Some of these files are very important and should not be deleted except with extreme caution - like GI (Grid Information) files which store Coordinate Systems and other important details.

Some other files are temporary and I am often asked by users about which file types are safe to delete at the end of a project.  Here's a few from my list.

• _filename.ext -- File names that begin with an underscore are usually temporary files that are recreated when the function is re-run, such as gridding and contouring. One exception to watch for: ITR colour files for geochemical database channels (e.g _Cu.itr).
• i0, i3, i4, o0, o3, o4 -- These are import and export templates.
• GD~ -- This file is a temporary database file. It often disappears when the GDB is closed.
• INI -- Configuration settings.  Be careful not to delete custom INI files in Target and Target for ArcGIS.
• GM -- Geosoft MAP extension for Geosoft's MapInfo plugin.
• MDF -- Map definition file, used in map creation.
• LOG -- Log file or general report, ofen related to imports in Target and Target for ArcGIS.

Colour Bars for Everything

Colour bar legends are important to include when sharing colour images. 

You can add a colour bar to your map to show the colour distribution of a voxel using the Grid and Image > Display > Colour Legend Bar option.  Be sure to order the Base view on top of the 3D view so that you can see the colour bar group.

In the next release, this will be even easier to do, with a plot option inside the 3D Viewer.

 

Exploding Contours to create a Topography Profile

A contour dataset is a common way to receive topography data.   Like many other groups in the public sector, the City of Vancouver recently made 2- and 10-metre contours available. 

Target users know that if they want to see a topo profile in section, then the topography needs to be interpolated into a raster (commonly Geosoft GRD files are used for this).  If I start with an ESRI shape file of topography contours, then I first need to convert the attributed polylines to a points so they can be used to create a grid.

Since v7.1, I can do this right in Target or Oasis montaj.  When importing the shape file, select the option to Import data to New database with shape database(s). 

This will save the coordinates of polyline or polygon entity nodes in a separate database.  Then use the gridding algorithm of your choice to create a topography grid or 'digital elevation model'.

Target for ArcGIS users! Check out ETGeoWizards for the polyline to point conversion tool. Then use the point feature class with Target for ArcGIS's minimum curvature gridding.

Displaying Target for ArcGIS data in ArcScene

I am often asked how to display 3D drilling data from Target for ArcGIS in ArcScene.  Voxels and assay results are important additions to 3D maps in the exploration industry.  There are some easy methods for bringing this data into ESRI’s 3D environment.

Drillhole assay data can be displayed using a few different methods depending on your needs.  For a quick visual display, use the Plan Map tool with shapefile output and the post values option for assay fields in the Data tab.  The point shapefiles are not Z aware, but you can use the RL field as your base heights in ArcScene.

 
If you prefer to have a more realistic polyline that shows sample interval lengths, you can use linear referencing. Traces from the Plan Map tool are Z aware polylines that can be turned into “routes” and used to display from-to assay data.  Use the Hole field for the Route ID, and Top and Bot fields as measures. Then export the attribute tables of the assay point shapefiles (created as posted values in the Plan Map tool) as DBF tables and use them to create Route Event Layers where the From and To fields are the measures. These route events can be displayed and symbolized in ArcScene. 

Linear referencing can also be used to display assay information on 2D sections maps with ArcGIS symbology applied.  Just use the 2D Traces shapefile created in the Section Map tool instead of the 3D Traces shapefile from the Plan Map tool. 

 
Although ESRI does not currently support a voxel datatype, the voxel data created in Target for ArcGIS can still be displayed in ArcScene.  Export your voxel model to an XYZ text file using the Voxel menu option "XYZ from Voxel". Then convert the XYZ points to a shapefile or feature class using the Add X,Y Data tool.  In ArcScene, add your point feature layer and symbolize the data using 3D cube simple marker symbols.  Set the symbol size to the original voxel cell size so the resulting cubes are the right size.