OMNIWeb Context Sensitive Help
Contents
This document was written in the style of a Usenet FAQ so that it can quickly
answer frequently asked questions about the OMNIWeb system.
OMNIWeb is a Web-based data browse and retrieval tool for the NSSDC OMNI data set. OMNIWeb was established to facilitate user access to selected parameters of heliospheric interest in the OMNI data set, which is a composite of multiple sources for the magnetic field, solar wind plasma flow parameters, and some energetic particle fluxes, found in space just outside the Earth's magnetosphere.
OMNIWeb allows the user to select a time span and produce a plot or listing of the various fields in the OMNI data set.
- Plots are displayed on the user's WWW browser as inline images.
- Retrieved data is either displayed on the user's WWW browser as a listing or placed in NSSDC's anonymous FTP site with a hyperlink to download.
For example, see this 10K GIF image for a sample time series plot created with OMNIWeb.
All the things required to access OMNIWeb are listed below.
- Good connection to the Internet (10kb/sec or better transfer rate is recommended.)
- A graphical WWW browser that supports "forms" such as Netscape or NCSA Mosaic.
The paper "NSSDC OMNIWeb: The First Space Physics WWW-Based Data Browsing and Retrieval System" was presented at the Third International WWW Conference '95 in Germany. The slides used in the talk are also available.
A brief article "New Access to OMNI Data Through the World Wide Web"
about OMNIWeb is available in the NSSDC Newsletter.
The latest developments of the OMNIWeb system are found in the OMNIWeb News document.
The OMNIWeb system comprises five major components (Home Page, Data Explorer, Feedback, News, and Help document), which represents the user's conceptual view of OMNIWeb. This view is depicted in Figure 1.0 below.
The OMNIWeb Home Page links all of these components together and is the logical starting point for interaction with the OMNIWeb system.
A control panel comprising four graphic buttons are present near the bottom of every "page". The control panel, in conjunction with the "back" button on WWW browsers, allow the user to navigate the OMNIWeb system.
Figure 1. OMNIWeb System Diagram
The Home Page is the starting point for interactions with the OMNIWeb system. It includes
links to the OMNIWeb News document and the OMNIWeb Data Explorer tool. A control panel at
the bottom of the page provides links to important information and functions of the
OMNIWeb system.
With the OMNIWeb Data Explorer form, the user selects an activity, enters start and
stop dates, and picks variables to plot or retrieve. Options are also available
for advanced plotting features, converting data to various formats, or
downloading or listing data.
To use the OMNIWeb Data Explorer, follow the steps below:
Select an activity
- Plot or retrieve data to perform the corresponding activity.
Enter start and stop dates (use yyyymmdd or yyyyddd format)
The start and stop dates indicate the time period of interest. The dates can be entered in the following date formats:
YYYYMMDD
- YYYY indicates a 4-digit year (1973,1974,1975,...)
- MM is a 2-digit month (Jan=01, Feb=02, ..., Dec=12)
- DD indicates a 2-digit day number (01-31)
YYYYDDD
- YYYY indicates a 4-digit year (73,74,75,...)
- DDD indicates a 3-digit day of year number (001-366)
For example, January 1, 1992 equals 19920101 in YYYYMMDD format and 1992001 in YYYYDDD format. The availability of the data for magnetic field and plasma parameters is available in the data document.
Select Resolution
The data is stored as hourly averaged values (24 records per day), which is
the default resolution to access. The user may also request daily averaged values to compute the average over every 24-hours of data into a single value. This is useful for trend analysis of large periods of time. Daily resolution is only available in plots and ASCII listings.
Basic Plotting
- Enter a start and stop date within the valid ranges.
- Select up to five variables from the variable list.
- "Click" on the "Submit" button.
Basic Retrieving
- Enter a start and stop date within the valid ranges.
- Select any variable from the variable list.
- Select a data delivery option. You have a choice of listing the data to your WWW browser
or
placing it in NSSDC's FTP site for later downloading. Data delivered to the FTP site will be
deleted in 48 hours.
- Select a data format for downloading. The default is ASCII.
- "Click" on the "Submit" button.
Advanced Plotting
- Enter a start and stop time within the valid ranges.
- Select up to four variables from the variable list.
- Scroll down to near the bottom of the page and specify various plot options.
- "Click" on the "Submit" button.
Please see the Advanced Plotting document for more
information about advanced plotting features.
The plotting option allows the user to generate times series plots for up to four fields from the available data.
The Data Explorer passes the selected fields to a CGI script, which in cooperation with graphical data analysis software,
creates a GIF or PostScript file of the plots that is transmitted back to the user's WWW browser.
The data may be retrieved directly to the WWW browser as an ASCII listing or a a subsetted data file may be created for downloading.
The ASCII listing is a subset of data specified by the start/stop dates and the specified variables from the data set.
The listing is followed by a format description of the selected variables. This option is best for browsing small amounts of data.
If the download option is chosen, the user has the additional option of converting the data to one of the formats listed below. The binary formats include the machine-independent NSSDC Common Data Format (CDF). Further information on CDF is available from the CDF Home Page with the URL https://nssdc.gsfc.nasa.gov/cdf/cdf_home.html.
Note that daily resolution values are displayed in listings and plots
for browsing long time periods, but not in generated CDF or binary files. All downloaded CDF and raw binary files will be in hourly resolution, which are intended for further analysis.
For information on the spacecraft and data, please see the OMNIWeb Data document.
To collect ideas and user opinion on how OMNIWeb could be further improved, we have provided
a forms-based feedback mechanism available from the OMNIWeb system.
Further enhancements to the OMNIWeb system will be primarily driven by user requests. From our user's requests,
we have added many advanced browsing options to improve our data browsing service.
The OMNIWeb News document contains important announcements about the OMNIWeb system.
It was created to allow the user to quickly see updates, enhancements, and other
changes to the system.
For information on OMNI data, please see the OMNIWeb Data document.
OMNIWeb is designed to be as user friendly as possible, therefore it communicates all
detectable errors to the user or to the developers. A list of errors and their
explanation are available from the OMNIWeb Error document.
This section contains various questions asked by OMNIWeb users and the
answers provided by SPDF staff.
If you have any questions/comments about OMNIWEB system, contact:
Dr. Natalia Papitashvili,
Mail Code 672,
NASA/Goddard Space Flight Center, Greenbelt, MD 20771
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