The following statistics describes the accuracy of the final grid before smoothing:
Root mean squared error = 2351 mg/l
Mean error = -4.8 mg/l
Mean Standardized Error: 0.0109
Root mean square standardized: 1.000189
Average Standard error: 2077.185
The grid was smoothed using focal statistics which calculates for each input cell location a statistic of the values within a specified neighbourhood around it, in this case 5 km radius, smoothing the surface using the average cell value.
Selection criteria for AWWID chemical analyses and formation water analysis from drillstem tests and production wells, as well as the final data set used for interpolation of this grid are documented in the metadata for AGS DIG 2017-0026.
Step 1 (Modelling the surface): A simple kriging algorithm was used in the ArcMap Geostatistical Analyst extension to interpolate the TDS values and create a grid of the TDS surface of the Wapiti / Belly River HSU.
Method Report:
Method: Kriging
Type: Simple
Transformation: Normal Score
Output type: Prediction
Trend type: None
Variogram: Semivariogram
Number of lags: 40
Lag size: 6800
Nugget:0.168
Measurement error percentage: 100
Model type: Spherical
Range: 272000
Anisotropy: No
Partial sill: 1.09
Total points: 908
Cell Size: 1000 m
Root mean square error: 2351 mg/L
Step 2 (Grid Alterations): The final grid was clipped to the extent of Wapiti / Belly River HSU. Focal statistics with circular neighborhood with radius of 5 km was performed on the final grid to smooth the surface.