Geosoft - Exploring With Data

Displaying Grid Profiles along a Section

When displaying grid profiles, sometimes you need to combine your data in one display that includes multiple scales. In this post, I’ll review an option that makes it easier to deal with this challenge.

Using Target or the Oasis montaj Drillhole extension, you can add profiles to section maps.

Depending on the scale of your section and the page size you are working with, it can be difficult to see subtle features in the gridded data. If this is the case, it is helpful to know that there is another way to see the profiles of gridded data along a section.

1. Plot the section trace on a plan map

2. Use Grid Profile to save various grid values along the trace to a new line in a new or existing database. I prefer a *new* database as there will be a new channel for each grid.

3. Display the profiles for each channel and customize the visualization of the profile to your preference. (To do this, right click on the profile and select Profile Options...)

4. Right click and select Plot Profile Figure... 

and this will display your grid profiles along the section in a new map.

Software upgrade available - August 21, 2012

The following Geosoft software upgrades are now available to all maintained customers:

• Oasis montaj 7.5.1
• Oasis montaj - Educational 7.5.1
• Target 7.5.1
• Target for ArcGIS 3.5.1
• Geochemistry for ArcGIS 2.5.1
• Plug-in for ArcGIS 2.5.1 (this is a free product, no maintenance is required)

This release includes support for ArcGIS 10.1 as well as a number of maintenance fixes.  Click the Geosoft Product above to see detailed release notes for this software upgrade and instructions on how to update.

Adding Bing Maps imagery to Geosoft maps

Bing Maps published its largest satellite release to date this past month, and with Geosoft’s latest software release, Oasis montaj and Target 7.5, Bing Maps imagery can be added as a map group.

Bing Maps is a web mapping service provided as a part of Microsoft's Bing suite of search engines and powered by the Bing Maps for Enterprise framework. Bing’s satellite release adds 165 terabytes of new data which cover 38 million square kilometres. Imagery from North America, South America, Africa, Australia, Europe and Asia are included.

To access the Bing Maps service within Geosoft, go to Seek Data > Add Bing Maps Imagery. You can add Aerial, Road or a Hybrid image as a map group. Note that you will need to be connected to the Internet and logged in with your Geosoft ID. Use of the service is subject to Microsoft's data license requirements. Learn more in this How-To article. 

When you are offline, a grey disconnected image will appear in place of the Bing Maps layer until you connect again. As the Bing Maps map group is powered by an online service, your map will display the latest data every time you use it.

Drag and drop shortcuts in Oasis montaj - time savers and hidden gems

A question came through our twitter feed asking what is the best way to import many XYZ files into Oasis montaj.  The answer:  Select all the XYZ files in Windows Explorer, drag them and drop them into a new, empty Geosoft database.  

There are several useful drag-and-drop shortcuts in Oasis montaj and Target, but because of their nature (they are drag-and-drop methods after all!), they can often be overlooked when they are most helpful. 

Drag-and-drop can be used to:

Simplify multi-file operations:

• Drag-and-drop a Geosoft map, grid, or database from Windows Explorer into Oasis montaj.  This is a quick way to add files to a new Project.
• Drag-and-drop a map, grid, or database from the Project Explorer to the Oasis montaj desktop. This is a quick way to open these file types.
• Drag-and-drop XYZ files to a new database.

Move map groups from one map to another:

• Drag-and-drop a grid from the Project Explorer to an open map.  (This is the same as Display Single grid, and if the auto-shading option is on, the dropped grid will be shaded.)
• Drag-and-drop a single map group from one map to another map. (This is the same as right-click option to Copy and Paste Georeferenced.)

Transfer map layers from 2D maps to 3D views:

• In Oasis montaj 7.5 you can drag and drop map layers from Target section maps to the 3D Viewer and the layers will appear georeferenced in 3D space. 

You can see some of these drag-and-drop methods in action in this video.

Gridding algorithms - which one do I choose?

A customer commented recently that the kriging algorithm was taking a lot of time to complete for a large dataset.  Kriging is computationally expensive and because his dataset had several million points, we suggested he try IDW, direct gridding or minimum curvature instead.

Here is a list of the gridding algorithms available and a brief description of why they might be chosen: 

Minimum Curvature can be used when data is sparsely sampled and the surface is expected to be relatively smooth or continuous between data points.

Kriging is a geostatistical method that determines the most probable value at each grid node based on a statistical analysis of the entire data set.  Because of this, it is computationally expensive. Kriging can be used if the data is variable between sample locations, known to be statistical in nature, or for poorly sampled/clustered data. This algorithm is available for 2D and 3D gridding.

Bi-directional line gridding is designed to rapidly interpolate roughly parallel line-based data, especially if there is a high sample density down the lines relative to the line separation. The interpolation uses linear, minimum curvature or Akima splines. It is only available in Oasis montaj and cannot be used to interpolate randomly distributed XYZ data.

Tin gridding results in output grid cell values that closely match the magnitude of the original data at known XY positions.  The interpolation is entirely local and every point will be influenced either by its nearest or natural neighbours depending on the parameter chosen.  Tin gridding can be used for irregularly sampled data. This algorithm is available in Oasis montaj and Target.  In Target for ArcGIS, this algorithm is only available when gridding drillhole data for a plan maps, section maps or plan grids in 3D maps.

Inverse distance weighted gridding (IDW) can be used when data is sparsely sampled and the surface is not expected to be smooth or continuous between data points. The data points are weighted so that the influence of one point relative to another declines with distance.  Three key parameters that can be set that will influence the interpolation are search radius, weighting power and weighting slope. IDW can be used to create 2D grids and in the April 2012 release, IDW will also be an option for 3D gridding.

Direct gridding is designed for highly sampled or oversampled data such as LiDAR.  The output value will be determined based on the minimum, maximum or the mean of the data points that fall within the grid cell. This algorithm is available in Oasis montaj and Target for 2D gridding.  In the April 2012 release, direct gridding will also be an option for 3D gridding in Oasis montaj.

Coordinate Systems: Set it and forget it

Someone asked me at Roundup about a grid that was not displaying in their map as they expected. It turned out that the map's data view did not have a coordinate system and the grid was referenced in a different coordinate system, so it didn't reproject on-the-fly.  This could happen to anyone!  Here's a bit of advice to keep it from happening to you:

Import, Set, Save.

When you import a new dataset, often to a Geosoft Database (*.GDB), be sure to set the coordinate system right away using the Coordinates menu Coordinate System... option.  This will ensure that all grids, maps, and other datasets that you create from this database will also have a coordinate system. 

Then save your work. I like to use the Save Project toolbar button.

Updating Target Plan and Section Maps

Updating section maps is a common task for Target users.  This topic came up more than once at the Roundup and I have written about it before.  There are three main ways that you can update your Target maps. The first two have been outlined in earlier posts.

1. Recreate Target Section or Plan Map - This option is available by right clicking on the Target map and will open the plotting tool with all the parameters from the current map.  If you don't change anything, then your map will be overwritten with updated data from the drillhole project.  This was described in Recreating plots and replotting holes in Target

2. Replot Holes on Target Section or Plan Map - This is useful when you have a map with annotations or interpretations but need to update the map with new holes or new downhole data.  The map is not overwritten, so any custom layers you have added are maintained but the hole traces and downhole data groups are updated with the most recent data.  This was also described in an earlier post: Replot Holes on Existing Plan or Section.

3. Map Tag Names or Save Map As - The third option allows for a little more freedom, especially when you have additional groups such as images, interpretations, or other imported data in your plan or section map.  The first step is to use different names for the original and updated maps. One way to do this is to change the "Tag Name" when recreating the section or plan (as described in #1).  I often forget to change the tag name when recreating the section or plan so I like to use Map > Save Map As to save the original map with another name.  Appending the date at the end of the file name works well.  Then the additional groups in the original map can be added to the updated plan or section by selecting them (use Ctrl to select multiple groups) in the Map View/Group Manager and dragging and dropping them into the section view.

Displaying Drill Hole 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 the "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 types of data 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.