Surface Interpolation Tool - Spline
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Interpolation Tool
Step 1: Load CSV file Download example here
Step 2: Create Surface
Results
Surface Transparency
Legend
Tool Description

"The Spline tool uses an interpolation method that estimates values using a mathematical function that minimizes overall surface curvature, resulting in a smooth surface that passes exactly through the input points." -Esri, 2014. For more information, see the ArcGIS documentation here.

Sample data from Global Weather Data for SWAT (http://globalweather.tamu.edu)

+
60km
40mi