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Giovanni-3 Operation Technical Summary: Comparison Plot Overlay

Comparison Plot Overlay
(also called Multi-Parameter Area Plot)

The Comparison Plot Overlay operation for Giovanni-3 plots two data parameters on the same Lat-Lon area plot. The values of the first data parameter are visualized using a color scale (palette). The values of the second parameter are overlain on the color plot using contour lines labeled with the parameter values, spaced at discrete intervals.

The appearance of the Comparison Plot Overlay output can be adjusted by options listed below.

Image Size 

  • Image X size: Adjust the image x-size (unit: number of pixels)
  • Image Y size: Adjust the image y-size (unit: number of pixels)

Color Palette
There are three color palette modes (this is also true for the standard Lat-Lon area plot):

  • Predefined – The Giovanni system uses the pre-defined plot value range of each parameter and a pre-defined color palette is applied tocreate the color image. This is the default option.
  • Dynamic – This option uses the minimum and maximum data value of each parameter to determine the plot value range, and uses a standard rainbow color palette for the first parameter to create the color image.
  • Custom – This option allows users to input desired minimum and maximum values and to use the standard rainbow color palette for the first parameter.  This plotting option produces 10 gradations to assign values to the colors in the color palette, spaced linearly from the minimum to the maximum value. Caution: The user-defined min/max values are used for both parameters, which may cause problems if the value range of the first parameter is significantly different from the value range of the second parameter.

This option is only applied to the first parameter to make the color image.

  • Yes – Apply the smoothing function first, and then create a shaded contour plot.  The smooth function uses linear interpolation to create the finer grid shaded contour plot.
  • No – Displays filled grid boxes with no smoothing function applied.

There are four projection options:

  • Cylindrical Equidistant
  • North Polar Stereo
  • South Polar Stereo
  • Robinson

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

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