Dip Gridding

Dip Gridding is the newest addition to the RockWorks suite of gridding tools. This algorithm biases the surface modeling based on the dip-direction and dip-angle of the control points. The algorithm also accomodates points for which the dip is unknown. 

This gridding method is applicable to geologic structure modeling (elevations) only.

Here's how it works: Consider the control points listed and mapped within the following diagram. Each of the points has a z-value (elevation) of zero. A contour map would be non-sensical because a gridded surface would be a horizontal plane.

Now, let's say that we have dip information (e.g. strike & dip or dip-direction & dip-angle) for some of these points as shown within the diagram below:

The new dip-gridding algorithm will use the dip information (for the points that have it) to construct imaginary planes that are used to bias the modeling as shown by the example shown below.  Specifically, the algorithm computes the plane represented by each strike and dip measurement point. Then for each grid node it determines the elevation at the intersection of that node's XY point and the planes of either all of the structural sample points or a specific number of neighboring points. It computes a distance-weighted average of those elevations. You can also apply a distance filter so that distant structural points won't influence a node.

Notice how the points without dip information constrain the modeling.

Menu Options

• Structural Points:  
  • Use All: Choose this option if all of the points with structural measurements are to be used in the interpolation for all grid nodes.
  • Use Closest: Choose this if you want to limit the influence of the structural points.
    • Maximum number of points: Use this setting to define the number of closest structure points to take into account when interpolating a node value.
    
     
• Use Distance Cutoff:  Insert a check in this box if you want to apply a distance filter to this process, and type into the prompt the map distance, in your grid model units, beyond which a structure point will not have any influence on a grid node. This will represent horizontal distance between the grid node and the control point.
   

Notes

This new gridding method has resulted in the following additions to the program:

• A new program titled "Dip Direction & Angle -> Grid" has been added to the RockWorks | Utilities | Planes menu. This program will create a structural grid and contour map using the new dip-gridding algorithm and plot (as an option) strike-and-dip symbols at the control point locations.
• The Utilities | Map | Grid-Based Map menu offers input prompts for direction and dip angle, allows you to specify direction format and declination correction.
• A new algorithm titled "Dip" has been added to the Gridding Options menu along with a group of options pertaining to the nuances of dip gridding.
• The Stratigraphy table within the RockWorks Borehole Manager now includes fields for entering optional dip-direction and dip-angle field for the superface (top) and subface (bottom) contacts.

Back to Grid Method Summary

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