Common Data Format Update

Volume 10, Number 2, September 1994
by Greg Goucher and Jason Mathews
Version 2.5 of the CDF software and documentation is currently under development and scheduled for release in late fall. The beta version of the software is scheduled for release in late September and will be available via anonymous ftp. CDF 2.5 will consist of the Macintosh port, modification to the way in which attributes are handled in memory to compensate for the memory limitation on the Macintosh and IBM PCs, and additional error checking capabilities in an attempt to detect corrupted CDFs.

The CDF Tools and Utility programs will be developed with the standard Macintosh user interface containing dialog boxes to specify qualifiers and options unique to that program. Rather than being contained in one publication, the documentation will be divided up into three separate documents: CDF C Programmers Guide, CDF Fortran Programmers Guide, and a CDF Users Guide. In addition, the CDF User Support Office had sent out a survey to all of our users and have received approximately 100 responses. We will be compiling the results and mailing them back to users soon.

Various lossless data compression algorithms are being evaluated for incorporation into future (i.e. later then 2.5) versions of the CDF library. Various implementations of compression algorithms are being tested and the results plotted with IDL to maximize the compression ratio vs. compression time. Lossy compression algorithms may be evaluated later, if enough users show interest.

The CDF anonymous ftp directory on ncgl.gsfc.nasa.gov (128.183.10.238) now includes application programs in addition to the CDF software. The following software is available in the specified directories.

- /pub/cdf/apps/graphics/mac CMIT: CDF Image Tool for the Macintosh
- /pub/cdf/apps/graphics/msdos CWIT: CDF Image Tool for the MS-Windows
- /pub/cdf/apps/graphics/unix CXIT: CDF Image Tool for X-Windows

CMIT, CWIT, and CXIT are 2-D scientific visualization tools that display map images using CDF datasets. Data in geographic and magnetic coordinates can be mapped to the Earth using orthographic, azimuthal, or mollweide projections, with overlays of a coordinate grid and/or coastlines.

- /pub/cdf/apps/conversions MakeCDF: Converts binary and ASCII data to CDF in compliance with the "ISTP Standards and Guidelines" (12/92) document.

- /pub/cdf/apps/utils CheckCDF: Recursively searches a directory tree for CDFs (MSDOS, UNIX, and VMS); opens files and samples data to verify and validate CDFs.

All software is public domain and freely distributed by NSSDC. For users that who have CDF based applications and would like the CDF staff to freely distribute them or information about them send a brief description of your product to Jason Mathews (mathews@nssdca.gsfc.nasa.gov).

A CDF Tech Brief is available on the Space Science Data Operations Office (SSDOO) WWW home page (http://bolero.gsfc.nasa.gov/c630/ssdoo_main.html). A link set up from the NSSDC home page to allow users to reference the CDF Tech Brief, the anonymous ftp account for software retrieval, and to access a list of CDF most Frequently Asked Questions (FAQs). A new paper about CDF, entitled "A Comprehensive Look at CDF," is now available in hard copy via NSSDC Request Coordination Office or through the CDF Support Office (cdfsupport@nssdca.gsfc.nasa.gov). It soon will be available online in postscript format.

The CDF staff assisted the International Solar Terrestrial Physics (ISTP) CD-ROMs Project in performing low-level CDF validation of the ISTP CD-ROMS on MS-DOS, UNIX, and VMS platforms. The test not only helped to detect corrupted CDFs, but also enabled us to uncover a VMS CD-ROM driver problem. The CDF software was modified to compensate for this defect and will now read existing CDFs flawlessly. As a result of the testing procedures, the CDF staff developed a tool entitled "CheckCDF" that transparently parses a directory tree of a given CD-ROM, opens every CDF, reads a subset of variables and metadata values, and records obvious errors. This tool verifies that the CDF is physically valid and should be extremely useful to the ISTP validation group (and other makers of CDF CD-ROMs) as part of their validation process. In addition, the CDF staff produced CD-ROM-mounting documentation that will accompany every ISTP CD-ROM to provide users with proper mounting instructions for each supported platform.

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Author:Miranda Beall
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 21 Nov 1996 [EDG]