Creating a grid surface by IDW2

s aloglu 8 years ago in Resource Estimation updated 8 years ago 4

Hi All,
I created top surface of a coal seam by DTM-Create Surfce and also by GRID Create (IDW2)
as seen below,

Image 812
Image 813
and a section view;

Image 814

it is said that, gridding is the better method for creating surfaces of features such as coal seams, weathering surfaces etc.Also,surface can be extented till boundary, which is good. However; IDW method creates dips and humps at every drillhole. These dips and humps looks unrealistic. In section view, there is a big elevetion diffrence, between two surfaces.According to which model, underground design will be done is a another issue.
any ideas to eliminate these humps and dips?

Good day.

It may be best to use an alternative algorithm. I would recommend using omnidirectional kriging and using the Basic General Linear semi variogram, don’t tick set negative variogram weights to zero (as seen below).

When gridding data there are a variety of algorithms you can use.

IDW - assumes that each input point has a local influence that diminishes with distance.

Kriging - a method of interpolation that predicts unknown values from data observed at known locations, using semi variogarms.

Alternatively you can use, thin plate spline. With this method the points of the grid are interpolated using a Radial Base Function (RBF) which uses a Thin Plate Spline (TPS) kernel.

Thank you David,
Do I need to make a semi variogram model in order to determine nugget, slope, power, azimuth, and plunge or Can ı use default parameters?


For your few holes, you can simply use the default variogram. I doubt you would be able to model a variogram with the small data set you have.
Okay, I will try.
thank you.