Special Topics: Lab 8

This week's lab covered interpolation.  The example used was for water quality of Tampa Bay.  Four different techniques were used to display the Biochemical Oxygen Demand (BOD).  One technique used non spatial analysis.  The other technique was Thiessen interpolation.  This analysis used the Create Thiessen polygon tool.  The input features are the BOD points and the output is all fields.  A mask needed to be applied to only show the Thiessen polygon for Tampa Bay.  This used the points in each polygon to determine the whole value.

Technique three used Inverse Distance Weighting interpolation.  The IDW tool is used to perform this and I had to adjust the radius and power.  The last technique was spline.  The Spline tool was used for both regularized spline and tension.  Since there were points very close to each other, it caused high concentrations.  The points needed to be removed or the average to be calculated.

The results of the analysis show fairly similar for each technique except the regularized spline.  Below is an example of the tension spline.

Tension Spline