In Module 2.2 Surface Interpolation, we are introduced to different GIS techniques such as Thiessen, IDW and Spline. In addition, we compare and contrast the GIS techniques as well as interpret the results from each technique,
IDW map of Biochemical Oxygen Demand (BOD) readings in Tampa Bay
The surface interpolation lab provided us with forty-one (41) points that all contained a BOD value. Our goal was to use each of the interpolation techniques and evaluate the results.
The Thiessen technique indicates the area or region where each point is separate and distinct from all the other points, which provides for a visual look at where the points could have new coordinates and have the same value as the original points.
The IDW or Inverse Distance Weight technique indicates where interpolated points are plotted on the concept that points closer to each other have more influence as opposed to those further away.
The Spline technique has two variations, regular and tension, but they both work off the same principle of figuratively running a line through each point and a function determines the values of the interpolated points. Effective Spline tool use requires two conditions, the line must pass through each data point, and the line must keep the curvature to a minimum. The regular Spline may create values that are outside the sample point range. The tension Spline stays closer to the sample point range.
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