I am currently doing a final project, which I have to create a map of 2012 average precipitation of lower 48 states by using natural neighbour interpolation. The problem is that how can I get the data? I already have the data of 2012 from NOAA website in .CSV format. There are more than 80000 geographical locations in the file (http://www1.ncdc.noaa.gov/pub/orders/cdo/434898.csv) Would it be possible for me to use them to create the map and if anyone has any idea for me about getting a data please help.
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It sounds like you actually have the data already, but don't know how to use it to do the interpolation. You may want to revise your question to reflect this (as written and with the data tag, it's a different question). MyFamily's answer should get you going. You also may want to refer to the QGIS documentation page for the User Guide and Training Manual. There's a specific interpolation tutorial in the training manual.– Chris WCommented Nov 26, 2014 at 21:45
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2 Answers
Display XY Data > Natural Neighbor Interpolation - use the points you just created as the Input Point Features and the Z value set to average precipitation.
That will get you a raster surface of rainfall which you can represent how you choose.
*Be aware that with Natural Neighbor Interpolation, you may need to add some 'Anchor Points' so as to ensure complete coverage of the US.
Build Thiessen Polygons tool would probably accomplish this. Convert the csv to a point file and go from there.
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That tool would simply generate a polygon around each point. It doesn't really do any interpolation, or create shapes/contours around points with similar values.– Chris WCommented Nov 26, 2014 at 21:34