Lab 6: Interpolation

In this final lab, we are using the interpolation technique to estimate the rainfall amount between stations that recorded the amount of precipitation. Spatial Interpolation is a useful tool to estimate unknown values with known values. In doing so, I picked around 55 precipitation station where they have both season normal and season total data. These geographical location values are called sample points or control points. We are using these 55 already known values to predict/estimate the rainfall in the other unknown value area. There is no need to collect data from every single point in the country to get the result.

There were two methods in analyzing the data in this lab, IDW and Spline. IDW uses the 40 surrounding points that I picked to determine the new value for in-between points. This method works well when the point density is high, just like this case, the calculations for in-between points will be more accurate when the points are closed together. In other words, spline estimates values using a mathematical function that minimizes overall surface curvature.

There are slightly different result in IDW and Spline. I think the IDW shows the a better result than Spline. From the IDW maps, in terms of the normal and total rainfall, the north-east of the LA County has the least amount of rain fall. This is pretty close to the result in reality and what I entered from the precipitation data. The most "heaviest" rain fall located in the mid-east of the LA County where most of the dams are located. The dam would be one of the factor that provide climate factors that causing more amount of rainfall. The IDW shows a more "normal" result. For Spline, although there is heaviest rainfall located in the dam area, there is rainfall located in the west. This is not so true that compare to common sense and what I entered from the precipitation data. Normal and Total rainfall map both have influences on the difference of rainfall map. The difference in result may due to the differences between the interpolation method.  IDW calculated the value of  in-between points and spline estimates values using a mathematical function that minimizes overall surface curvature. Precipitation data would be best to use IDW to represent.