refining solid model - null values or 0?

[Jeremy Haynes]

Hi,

this is a revisit of an age old problem, but I'm modelling contaminant concentrations, and they are extending to the bottom of the model where there is not a data point to constrain the model. I generally use the detection limit as a lower limit, but is using a null value better?

Thanks,

Jeremy

[Edward Hakanson]

Hi. I face a similar problem when I map down hole clay samples. I have found that entering 0s works when what I want is a 2D log but if it is 3D then simply omitting values where there is no detection best. It really depends on how you want to display the data. However I would like to know what the optimum method is from an experienced Rockworks user.

[Jeremy Haynes]

Thanks Tom,

Just to clarify, if I put null values (i.e. typing "null" as a replacement for "ND") into my data sheet, then that acts as a real value that constrains the extrapolation (or interpolation as the case may be)? Can I use the word null or do I need to enter the "null" number?

Thanks again

Jeremy

[Jeremy Haynes]

Thanks, Tom. That explains a lot.

Cheers

Jeremy

[Jeremy Haynes]

Hi Tom,

I'm revisiting your explanation of the null value. If I understand you correctly, you're saying that use of the "null value (-1e27)" in the data sheet causes rockworks to "hang". Does this mean that one should not use the null value in the data sheet to represent a number? As an alternative, possibly "0" is better as a represents a "real number"?