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Helpful Hints on using the CDAW system

Supported Graphics Devices

The system (specifically graphics) supports a range of devices: the first query in the interface is thus what kind of terminal is being used. If the short list doesn't include your machine (note T4100 covers a range of Tektronix 41xx and 42xx terminals and emulators, X11 is appropriate for most X-windows access), then select HELP to see a much longer list of supported equipment. Note that "XHOST +" must be set before starting an X-windows session for graphics to be able to display. A second key note for all users is that the (vt100) PF1 through PF4 keys are used as control keys in the CDAW system, so a user does need to know their location on the particular device/emulator being used. As a special hint, character sequences on the SUN and other X-Windows platforms that will perform the equivalent of the PF1-PF4 keys are ESC shift-P though ESC shift-S (ESC and shift-P are a sequence of two keys, not simultaneous).

Functional Options

On entering the CDAW system, a user will see an initial "CDAW Subsystems Menu." Most selections are self-explanatory. The two primary functional options are "Data Manipulation" (soon to be retitled) and "Graphics". Functions included under "Data Manipulation" are: list values ; browse the values and attributes in data files; make algebraic calculations; use variouspre-defined functions; or use IDL to do your own manipulations. Graphics includes a variety of plot types and capabilities. Under both options, capabilities to save outputs to working files exist. On final exit from the CDAW system, an option is available to rename and save those files for subsequent retrieval from an area in the "anonymous" account of the NSSDC VAX cluster.

The Database

All data in the database is held in the form of the NSSDC-developed and maintained Common Data Format (CDF). CDF is a base format selected by both ISTP and the IACG for IASTP for data exchange. The CDAW databases are in the process now of upgrade to be compliant with specific style and structural guidelines adapted by ISTP and IACG and derived in the most part from lessons of the CDAW efforts that have preceded these programs. The CDAW system concept is thus that everything is done with data granules in CDF format: data is selected from one or more CDFs, then can be manipulated as desired and combined into a new CDF, from which parameters can then be plotted (inconjunction with parameters from other CDFs if desired). CDFs support storage of multi-dimensional arrays, and allow attributes to be defined as needed for any particular data set. Certain widely-used attributes are useful for such things as identifying the data source, tracking data revisions, describing instrument operation, providing labels and units for the plot parameters, etc. Others help speed the processing, or flag certain kinds of quantities, so that, for example, two longitude values of +175 and -175 degrees will be averaged to 180 degrees, rather than 0, if a running average is needed.

Data Manipulation

Selecting "Data Manipulation" moves to a submenu indicating the various list and analysis functions available. "Graphics" passes first to a submenu where "Graphics Utilities Menu" is appropriate for remote users of the public system. Graphics then proceeds in two distinct steps, first to select the data files from which data is to be plotted and to specify/execute the plots desired. Users are recommended to use the "CDAW 6 and CDAW 7" or "CDAW 8" CDF Data File Selection" options (which feature a full-screen "summary" interactive selection from "pop-up" lists of valid selections with context sensitive help) versus the "Manual CDF Data File Selection" (which features a TAE Classic interface). Under the "summary" interfaces, note that PF1 is used to exit the screen and PF4 is a data help key. The valid keyboard definitions are visible at all times on the screen, with instructions and messages in a controlled "message" area.

Plotting

Once files are selected and linked to the session, detailed plot specification for standard X-Y and "Panel"(multiple stacked X-Y) plots is possible via (the recommended) "CDAW Summary Screen"(option 11) or various TAE Classic screens (other options). The CDAW Summary Screen actually consists of two screens (toggled by PF2) that define both general plot properties and specific variables to be plotted. The various system options are described in the CDAW User's Guide (available in hardcopy from CRUSO and to be put on-line in the near future). On "adequate" network links, the "Low/Software" character fonts will give nicer looking labels. Users not familiar with issues in using multi-dimensional CDFs will probably have best results staying with the "Simplified" setting of the filter interface. PF1 is again used to initiate plotting.

For "Plot Type" users may find that most magnetospheric data are more conveniently plotted using the "panel plot", which displays three panels on the screen, with up to two parameters per plot (color-coded and marked with symbols for identification). Less commonly used is the "X-Y plot", where up to five parameters are displayed on a single panel. An option at plot time is to save the plot to a standard plot file (if a "save file" was previously named), from which it can be re-displayed by use of the "Post-Processor" option. Re-display can be made to any device, not limited to the one that originally made the plot.

The above plot types can be made via the "Summary Screen," but a number of other plot types and some other system options are only available via the TAE options. Users of TAE should remember that once something is selected, you must then give the RUN command (not "EXIT") before it will be effective. Image display in this system in particular is functionally quite capable but is not highly user friendly to configure and usually operates quite slowly. SPDF/NSSDC have developed an image-display program, CXIT, (operating on a SUN with X-Windows, not now accessible on NODIS) that is much faster and much more convenient for looking at the auroral images in CDAW 8.


* SPDF Home Page
-- R.E. McGuire, Head, Space Physics Data Facility (code 632), NASA/GSFC
(mcgurie@mail630.gsfc.nasa.gov)

-T.J. Kovalick, Space Physics Data Facility(Code 632), NASA/GSFC
(kovalick@mail630.gsfc.nasa.gov)
10/14/03 (TJK)