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).
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.
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.
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.
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
-T.J. Kovalick, Space Physics Data Facility(Code 632), NASA/GSFC