Polygon assign workflow for assigning drill hole intervals to cross section interp

Trevor Rabb 6 years ago in General updated by Barbara Stefanini 6 years ago 1

Ola Amigos!

This workflow is to assist you in assigning closed strings to drill hole intervals and works in the same manner as Wireframe > Calculations> Pierce Points. If you aren't sure if a string is open or closed, used the String > Utilities > Calculate area to determine if there are strings without area.

We recently had a set of cross section interpretation strings that we needed to be assigned to drill hole intervals. This workflow is a classic MM work around as you may not want to go to the expense of generating wireframes for your interpreted domains. We developed this workflow a couple years ago, and I have modified it slightly to speed things up using the wireframe assignment function. The workflow involves five main steps:

1. Generate discrete composite intervals along with coordinates that can be assigned later in the workflow

2. Rotate data; if your data is already on East - West (E-W) or North - South (N-S) sections you can bypass this step (you may be able to bypass this step if you do the wireframe assignment, but no garuntees!)

3. Flatten your polygons and composite intervals to normalized E-W or N-S section (alternatively, you can assign wireframes generated from the cross sectional file or Block models built on non-rotated grids)

4. Assign Polygons on your sections using the Strings > Utilities > polygon assign command for each section

5. Composite your assigned intervals and bring into the drill hole data base.

Step 1:

The first step is to create composite intervals from your drill hole data you are wishing to assign. In my example I used 0.5 m downhole intervals on the lithology as it was the most continuous downhole data. The scale of intervals will depend on the resolution of what you are modelling.

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The next steps would involve additing the new intervals to your drill hole database and calculating downhole coordinates for the composited intervals using Drillhole>Generate>3D Coordinates.

Step 2:

I would strongly suggest working with data that has been regularized to either a N-S or E-W grid. It may be possible to bypass this step if you wish to assign unique numeric section IDs to the points and polygons

Use the Survey -> Plane Grid  Conversion utility rotate your data. The end result is interval data that will be referenced to your drill hole database you only need to rotate the string and composite point data using the same convention

Step 3

You can either flatten your data to the sections or alternatively if you have many sections, you can assign wireframe attributes based on section easting or northing coordinates. In this example I assigned wireframe attributes using the wireframe > create from strings > center line to solids command from an array of lines that are parallel to the cross section orientation. In this case RL is set to the same value as my lateral offset that I desire, 12.5 m:


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Next assign the wireframes to the points and strings (i've just shown the polygons that I'm assigning)

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Check both sets of data in MM using Easting_WF as the X coordinate to ensure the data is plotting on N-S sections. 

Step 4

This part of the workflow plays into the way MM typically assign polygons based in plan view, and requires input to assign the coordinates in cross section to match the polyline. For this step I first made a formset for the string > utilities > polygon assign that I would later use in a macro:

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You'll notice that X field is the northing and the Y field is the RL. This is a workaround to complete the polygon assignment on section (the easting will stay constant if your sections are N-S oriented).

The filter for the fomset was set to the following, with %1 referencing the assigned wireframe easting:

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I then created a macro with all of the section lines of interp:

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Your composite file should now be fully asigned where there were points were contained within polygons.

The last step is to composite the assigned intervals using drillhole > compositing > geology

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Your final data will be composited and all you have to do is add it to the drill hole data base. The intervals should conform to the initial cross section if you have done everything correctly.

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Good luck!