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Giovanni Online Users Manual:4. Plot Preferences


Plot preference capabilities allow the Giovanni user to adjust various aspects of the output visualization to suit individual research needs. When "Generate Visualization " is selected, a new window opens which displays the plot, as well as all of the selection functions and plot preference menus. This display provides the opportunity to modify the values prior to adjust the image output.  

When the plot preferences have been selected, to generate the new visualization according to the designated preferences, click "Submit Refinements" below the plot preferences menus.   Clicking "Reset" will return all the preferences to the default values.

4.1 Image X/Y Size

Number of pixels in horizontal and vertical directions, allowing for the display of different image dimensions.

4.2 Decoration Flag

Setting the Decoration Flag to "No" will make the contour lines and labels less visible by changing the lines from black to white and by making both the label background and the label value white. This option facilitates the use of the image with other graphics packages, allowing more specific labeling.

4.3 Color Bar Type

The Area Plot and Hovmöller Plot output options in Giovanni provide three different color bar type (scale) options, as shown in the table below.  The default is the Pre-Defined option.

Color Bar Type Description
Dynamic Selects a linear color palette range that spans the entire range of values existing in the selected region. This option may not work well for data with a wide range of values.  However, for data with a fairly narrow range of values, the Dynamic option can be very effective.
Pre-Defined This plot preference utilizes the color palette which is initially provided with the data. For data sets with a logarithmic scale (notably oceanic chlorophyll a concentration), this will be the only logarithmic scale plotting option.
Custom User selects the range of values for a linear scale. In some cases, the Custom option can be used to duplicate a color scale selected by the Dynamic option for other time periods or regions. See Min/Max Color Value for how to set the values. The Custom option also includes 29 different color palette options. Some of these palettes, such as "Ocean", provide data value boundaries which improve distinction of high and low values in the generated visualization.

 

4.4 Min/Max Color Value

This option is used for the Custom Color Bar Type option.  The color value range is the range of physical parameter values for plotting provided by the user.

4.5 Smooth (yes/no)

This option applies only to the Lat-Lon Maps, Animations, Cross-sections, and Hovmöller (longitude-time, latitude-time) plots. 

Smooth (yes/no) Description
Yes Overlays the contour-shaded image on top of the grid-filled image. This allows the image to appear smooth, while including isolated data values where coverage is sparse.
No Each grid cell in the image is filled with the color representing its data value. All data values are properly represented, but the image has a pixelated or boxy appearance.


4.6 Plot Projections

This option applies to the Lat-Lon maps and Animations. An example of each projection, as generated by Giovanni, is shown below next to the projection name. The image is of OMI ozone data for September 15, 2006.

Cylindrical Equidistant
cylindrical equidistant projection of ozone data, south pole, September 15, 2006
North Polar Stereo
north polar projection, ozone data, September 15, 2006
South Polar Stereo
south polar projection, ozone data, September 15, 2006
Robinson
Robinson projection, south polar ozone, September 15, 2006

Notes:
A regional subset will be shown in a Cylindrical Equidistant projection for only the subsetted region.

For the Robinson projection, a regional data subset will be displayed on the full global Robinson projection. This may be hard to see if the selected region is small.

4.7 Time-Series Plot Preference Options

Time-series visualizations provide two plotting preference options.

Vertical Range (Y-axis): This option allows user-defined minimum and maximum values for the Y-axis (dependent variable), rather than the dynamically-selected range defined by the range of values in the output data. This option allows several different time-series to be plotted with the same Y-axis range, allowing better comparisons.

Overlay Plots: If this option (Overlay Flag = "yes") is selected for multiple parameter time-series, the parameters will be displayed in a single plot rather than in separate plots. Multiple Y-axes will be color-coded to correspond to the color of each parameter in the plot. This option is currently only functional for the Time-Series service and not for the Time-Series, Area Statistics (Time Series with statistics) service. For clarity, it is recommended that no more than five parameters be plotted in the overlay plot.

 


 

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