Question
Treatment of orphan composites
Does anyone have any ideas on how to "trick" Micromine to enable handling rejected short-length intervals during compositing process? The need is to be able to adjust composite lengths in a narrow vein situation so that "orphans" are incorporated in either: 1) The last full composite; or adjust all composite lengths in the geologic unit or drill hole to accommodate the orphan resulting in equal-length composites that are slightly different than the nominal length.
This is essential to maintain equal composite support for 3d estimation and to avoid systematic bias in situations where the orphan may be higher or lower grade material. A version of this question was posted 11 months ago, but I'm still trolling for ideas.
Answer
A semi-manual approach gives complete control over the compositing process. Create a new field called (say TRIGGER. This can initially be populated in several ways. For example you could use an expression to write either 0 or 1 to the field, based on the grade value. Alternatively, you could run an initial composite and run a merge, based on those results, back to the TRIGGER field.
Now add or remove "1" or "0" to the TRIGGER field to control the compositing process. You will re-run the composite using TRIGGER as the Grade field and set the Trigger value to (say) 0.5.
Not sure if that helps...
Don, based on your previous feedback we are currently working on both of those suggestions, which we plan to make available in Micromine 2018.
In the meantime, I'll try to come up with a two-stage compositing workflow that merges the orphans into the preceding composites.
One thing I forgot to mention: for now, you can do your compositing run without setting a minimum composite length. Then, in your estimation run you supply an interval length field, which reduces the potential bias caused by short, high grade intervals.
Yes, that's right and I have used this option before. We still have the support problem and it doesn't help with variography or change-of-support corrections. In a lot of cases, the problem of orphans isn't that significant. It's the narrow zones that generate large numbers of these.
No worries, Don.
I do appreciate your concerns about change of support with the smaller intervals, even when they are length-weighted. Just tinkering with possible work-arounds now.
Hi there! I saw this post dated a few months ago and I am wondering if anyone can suggest a solution to incorporate very short orphans in preceding composite. I am working on a historical resource with very limited assays over a few metres (only the massive ore sampled) and I would like to incorporate as much as possible in the interpolation. Many thanks
Hi Barbara. I hope your interest in having this improvement implemented in Micromine helps to move it to higher priority. No practical fix is currently available that I am aware of.
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Don, based on your previous feedback we are currently working on both of those suggestions, which we plan to make available in Micromine 2018.
In the meantime, I'll try to come up with a two-stage compositing workflow that merges the orphans into the preceding composites.