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You are here: GES DISC Home Giovanni - Interactive Visualization and Analysis Giovanni-3 Operation Technical Summary: Correlation Map

Giovanni-3 Operation Technical Summary: Correlation Map

Correlation Map (g3corr)

The Correlation Map operation (nicknamed "g3Corr") reads in two input data files from the previous time stitch operation. Each input file exclusively includesthe available data (correlation sample data) of one parameter. Each file has a 3-dimensional data structure with similar dimension sizes on latitude, longitude and time (x, y, t).

For each grid (x, y), the sample data in the whole time domain are collected from two input files and combined into a set of sample data pairs. If missing data from any parameter are found at any time step, the data pair at this time step will be removed and the sample size will be reduced. The effective sample size n at the grid (x, y) is thus determined.

Then the correlation coefficient is calculated based on the effective sample size n and the equation below:

equation for the calculation of the correlation coefficient r


P1 and P2 sample data equations

In these equations, r is the correlation coefficient at grid (x, y);  P1 and P2 present the sample data for two parameters respectively; and n is the effective sample size. If the effective sample size n is less than 2, the calculation is no longer executed and a default value r = 0 is given.

After completion of the calculations on all grids, an output data file is created with the correlation coefficient r and the effective sample size n at each grid point (x, y), and the output is sent to the Two-Dimensional Map Plot operation for visualization.


This Technical Summary is a draft version -- for additional information on this operation while the documentation is being completed, please send a message to GES DISC Help.

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Last updated: Nov 10, 2011 12:08 PM ET