GIOVANNI FAQ

Most remote-sensing instruments observe the Earth by scanning across the orbit track, which can be visualized as the line on the Earth surface directly below the orbital path traveled by the satellite. The scan area on either side of this line is called the scan swath. Most remote-sensing instruments do not have a scan swath wide enough so that the observational coverage on successive orbits overlaps. So for each day of observations, there are gaps between the scan swaths. However, the "polar orbit" configuration of many remote-sensing satellites can cause the scan swaths to overlap at higher latitudes, i.e., the polar regions, even though the scan swaths do not overlap over most of the Earth surface.

Giovanni output images from the "original" Giovanni system (now called Giovanni-2, or G2) are only in the GIF image format, and could not be put into Google Earth easily, if at all. Now, however, Giovanni-3 output images of area plots are available as KMZ files, which can be downloaded directly and opened in Google Earth. More capabilities of this download option were being developed at the time that this answer was written (December 2007).

How do I acknowledge the use of Giovanni in a research paper? If I use Giovanni should I have someone on the GES DISC staff as a co-author?

We have created a Web page which provides a basic acknowledgment statement, a general Giovanni reference, and considerations for co-authorship. Please consult this page for guidance. Note that the use of Giovanni should be acknowledged in any type of scientific media, particularly reports, posters, and meeting presentations, in addition to peer-reviewed papers published in scientific journals.

Recommended guidelines for use of Giovanni data in publications

How do I subscribe to the Giovanni-News mailing list?

It's easy! Here are the instructions:

1.  The email address is "majordomo@listserv.gsfc.nasa.gov"
2.  Put anything you want (or nothing) in the "Subject:" line
3.  The body of the message should just say "Subscribe giovanni-news" .
4.  Nothing else is required; send the message. You will receive an automatically-generated message confirming your subscription.

I waited several hours to generate a Giovanni visualization, and then it appeared that my request had failed. Why did that happen?

Giovanni is capable of generating an extensive variety of analyses and visualizations, but its computational capabilities do have limits. In particular, Giovanni analysis and visualization requests which involve data averaging over long time periods, over large geographic areas, and/or with data of high temporal resolution (notably daily or 3-hour data) place considerable demand on the capabilities of the system. Data processing requests with those characteristics have occasionally required so much time and computer resources that the request processing had to be terminated before completion. We are currently evaluating high-demand requests to determine how best to configure the system to handle them, particularly by improving system efficiency and performance to reduce the likelihood of a failure.

At this time, we would suggest the following general guidelines:

• If daily data is being analyzed, limit the time range for a time-series or a spatially-averaged map to a year or less.
• If 3-hour data is being used, limit the time range for a time-series or spatially-averaged map to three months or less.
• Whenever possible, analyze data over a defined spatial region, rather than globally.

Why I can't download the "Initial Data Retrieval" in ASCII in some Giovanni instances?

Downloading large volumes of high-resolution ASCII data has at times created a system performance problem, forcing us to disable this capability.  Users can still, however, download ASCII data for the visualization and analysis results. Depending on the size of the region a user selects, the magic number is an array size of 518,400.  This corresponds to about half the global data at 0.25° x 0.25° resolution.

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