QUESTION 2: Traditional Estimation Methods (25 marks) Copper grade at location xo is to be estimated using the Inverse Distance Weighting Technique (IDWT) as shown in Figure 1, where BH1 and BH2 are two diamond drill holes assayed by Im samples. The grid shown in Figure 1 is a 1 mx 1 m grid and the assay values shown are %Cu. "-99" represents missing value. "E" and "V" represent the "Easting and Elevation" coordinates. The grade estimation using the IDWT with power p can be written as: 3 & uld d! LE BH1 BH2 .99 -99 2.5 .99 2.1 1.3 -99 1.6 1.5 -99 + -99 Xo 2.7 -99 .99 .99 -99 -99 1.7 1.0 1.5 Im 0.7 .99 1m -99 -99 Figure 1 Estimation by Inverse Distance Technique (a) [18 marks] For p= 1 and 2, estimate the grade value at location xo using two different search neighbourhoods, one with a radius of 3.5m and the other with a radius of 4.5m. Show the steps and details of your calculations. Comment on the reliability of these estimates. (b) 17 marks] Compare and comment on the weight distribution for p= 1 and 2 calculated in (a). Explain the general impact of the p value on the final estimate and comment on the selection of a suitable p value in resource estimations using IDWT. Hints: (a) Each sample can be represented by a point located at the centre of the sample for the purpose of estimation; (b) Use the coordinate of the centre of a sample to calculate its distance to xo. QUESTION 2: Traditional Estimation Methods (25 marks) Copper grade at location xo is to be estimated using the Inverse Distance Weighting Technique (IDWT) as shown in Figure 1, where BH1 and BH2 are two diamond drill holes assayed by Im samples. The grid shown in Figure 1 is a 1 mx 1 m grid and the assay values shown are %Cu. "-99" represents missing value. "E" and "V" represent the "Easting and Elevation" coordinates. The grade estimation using the IDWT with power p can be written as: 3 & uld d! LE BH1 BH2 .99 -99 2.5 .99 2.1 1.3 -99 1.6 1.5 -99 + -99 Xo 2.7 -99 .99 .99 -99 -99 1.7 1.0 1.5 Im 0.7 .99 1m -99 -99 Figure 1 Estimation by Inverse Distance Technique (a) [18 marks] For p= 1 and 2, estimate the grade value at location xo using two different search neighbourhoods, one with a radius of 3.5m and the other with a radius of 4.5m. Show the steps and details of your calculations. Comment on the reliability of these estimates. (b) 17 marks] Compare and comment on the weight distribution for p= 1 and 2 calculated in (a). Explain the general impact of the p value on the final estimate and comment on the selection of a suitable p value in resource estimations using IDWT. Hints: (a) Each sample can be represented by a point located at the centre of the sample for the purpose of estimation; (b) Use the coordinate of the centre of a sample to calculate its distance to xo
