To get started using Giovanni and NEO, it is first necessary to know how to do some of their basic functions: choosing data, selecting a time period, selecting a region, creating images, and then selecting one of the various ways to analyze the data. This Functions page describes how to do basic functions like these in Giovanni and NEO.
Giovanni Functions
Area of Interest
The first thing to do on the Giovanni page is to select the area of interest. Giovanni provides a Java map that allows selection of an area by clicking-and-dragging the mouse. It takes a little bit of practice. Click on a location that will be one corner of a rectangular area, and hold the mouse button down as you drag to create the area. After the area is created, you can click on the center to move it around. In many of the cookbook pages, the latitude and longitude coordinates for specific areas are shown; instead of clicking and dragging the mouse, the coordinates can be entered in the boxes to the right of the map. It is also possible to zoom in for a closer look at an area to refine the size and boundaries.
The image below shows a selected area in red. The coordinates of the area are shown at right.
Below the map is the parameter selection list. The parameters shown here are for SeaWiFS data, and the chlorophyll a concentration parameter is selected.
Data Type, Plot Type, and Time Period
The next selections are for the Data Type, plot type, and Time Period.
The most common Data Type selection is "Parameter". The other data types are "Anomaly" and "Climatology". These are based on the 10-year mission average of SeaWiFS data, and are useful for finding unusual differences from normal conditions.
The Plot Type options are Lat-Lon Maps, Animations, Time-Series, and Hovmöller Plots. The primary options used in this cookbook are:
Lat-Lon Maps: Displays the values of the parameter averaged over the selected time period as a map.
Animations: Displays successive images of the selected region over the selected time-period. These images are not averaged over time.
Time-Series: Displays a plot of the average parameter value for the entire selected region for each time interval in the selected time period.
Hovmöller Plots: These plots are a more advanced way of viewing the change in a parameter over time and space.
Time-Period: The Time-Period is set by selecting the Begin Year and End Year, and the Begin Month and End Month (for Monthly data). The SeaWiFS 8-day data interface allows selection the beginning and ending 8-day periods in a year. Selections are made by clicking on the arrow button and then clicking on the desired time increments.
Other Options
There are three other options that may be used for Giovanni-generated plots.
Color Options: The data are provided with a Pre-defined color palette, which usually covers the entire range of the data fairly well. However, the Dynamic option can be used, which determines the range of data values in the region and time-period, and then creates a color scale using the maximum and minimum values as endpoints. The Customized option allows the user to select the maximum and minimum values.
Time-Series Plot Y-Axis Options: This option allows the user to adjust the scale of the parameter value in a time-series plot.
ASCII Output Resolution: The data in a map or time-series can be output as numerical values (ASCII text). This option specifies the spatial resolution of the numerical values obtained from a map output.
When all the selections are made, then either click the "Generate Plot" button to create the plot, or click "ASCII Output" to view the numerical values. The numerical values can be imported into a spreadsheet for additional analysis options, though that will not be covered in this cookbook.
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