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### Exercise 3937. Points 3, theme: Interpolation

Open exercise
1. Create an interpolated map using the nearest neighbour interpolation depicting annual the mean amount of precipitation in Estonia.
2. Which parts of Estonia get more precipitation (rain + snow)?
3. Why is the region distant from the West and South-West coast although wet Atlantic air currents come mainly from these directions?
Data: BALTISADEMED.xls

### Instructions

• Find Interpolation in the online calculator.
• Notice the needed data format [X] [Y] [Value].
• Select Calculate grid and Nearest neighbour.
• Arrange the annual precipitation column in Excel next to the X and Y coordinates and copy these three columns to the input cell in the calculator.
• Grid interval = 1000 assures the calculation interval 1 km in both directions, since the coordinates are in meters.
• Select Mask as: Estonian territory. Select which direction is in the first column. Hint: which coordinate expresses distance to the equator?
• Select Background Map as the satellit image would cover the interpolated values.
• Press Calculate and wait a while as there are more than 45 000 locations to interpolate.
• If you have software for using Idrisi rst format files you can download the grid and design the map as you like. Otherwise, the user has to get along with the image generated by the calculator.
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