0

Implicit Modelling Polygon Function

Geoff Elson 3 years ago in Geology updated by Richard Siddle 2 years ago 4

I really like the polygon implicit modelling function but I noticed it gets thrown by non-planar strings. For instance I interpret level plans but adjust a few points to snap to a drillhole. I don't see where it says strings must be planar.


Has anyone had this issue and found a way to work around it, other than manually adjusting the weights and rerunning.

The first picture is the scale for the output im weights, the second is the snapped string, (see the weight all grouped at the nodes of the string), the third is a planar string that spaces the weights as expected.

Image 2496

Image 2495

Image 2494

+2

Hi Geoff. There are some tips that I follow to avoid this kind of problem that you are facing. Let me show you some examples. Below is a snapped string that I've created.

This first thing I do is to clean it up with condition string. I delete single points, duplicate points, remove retraced lines and fix self interction.

For my situation it worked fine. 

But if this string was with too many points, the issue that you've had would be replicated.

So, always when possible try to simplify the string and then insert a reasonable number of points that will makes your model to honor the interpretation and avoid over points (more time consuming for interpolation and the issue might be replicated) . Below I simplify string and then regularize with 10 points. You could also regularize in Implicit Modelling Polygon Forms but I like to visualize it before and don't  need to modify tit in the form.



So, after conditioning and inserting a reasonable points it has generated the points correctly.


Other situation that you might face is even with strings it will not create, so there is a technique that I use to overcome that. The string below could not create the right points polarity points, only 0 ones.


So, to overcome that I split the string into 3 parts and give them a new join value. Give a new join value is very important to Micromine identify each segment separately as we input Join Field in Implicit Modelling Polygon.



So we run and Micromine will assign better. 





Nevertheless, when we use single segments the polarity might be inverted due to the orientation of the string. 






So, to overcome that we have to reverse the orientation of the string and run IM Polygon again.

So the polarity will be right

I hope it helps.

Cheers,

Pedro Nader

Just concluding, for your situation I would recommend split your string, give the segments a new JOIN value to interpolate it correctly and check the orientation of the strings to see if the positive and negative points were assigned correctly.

+1

Pedro, many thanks. This will help a great deal. Adding stings here and there to represent complex geometries will really make this tool awesome, and far superior to the old sectional wire-framing creation.

Hi Geoff, my usuall approach for modelling something that looks a like this with IM is to use the lithology/intrusion modeller. I generate a grade composite coded to mineralized and waste. Merge the mineralized/waste values to the assay, where I do some manual edits on what I want to include and exlude, then run the geology compoiste to give me a mineralized waste composite file for use in IM.


I then use strings as the input points, similar to those you have displayed tagged with a 0 value to guide the contact and the odd -1 and plus one where needed, like areas of no data where the IM blows out. I generally find that less is more in this case, so I try to add only a few points at a time. I prefer to do this as stings so I can visualize it better and also change a bunch of point values in one go. You can also add a filter field so you can expriment with including and excluding some strings/points, without delting them from the file.