Software Tool Suite Updated

by Rory O’Neill

The Alaska Satellite Facility is updating its downloadable suite of software tools used for SAR data manipulation. New versions of the tools can be accessed using a standard internet browser through an http download.

Executable binaries for Sun SOLARIS and Silicon Graph-ics IRIX operating system environments are now available. Source code (ANSI C) is also available, dependent upon tool-specific distribution guidelines imposed by ASF’s parent institution, the University of Alaska Fairbanks, and various U.S. federal agencies.

To access source code or U.S. Department of Commerce export-restricted tools, users must submit online forms or print and fax forms, and use a download password. Users with an approval form already on file at ASF User Services are asked to update their contact and institutional affiliation information.

• Departure from binary-encoded metadata: Within the SAR tools domain, ASF has eliminated the Data Descriptor Record (.ddr) file.

Instead, ASF’s proprietary metadata file definition has been expanded. This affects every tool and the associated metadata generating/parsing functionality has been encoded into the updated ASF metadata ANSI C library. The expanded .meta file is ASCII encoded, which enables metadata keyword value viewing or editing with any text editor—an improvement over the binary-encoded approach associated with the .ddr file. Complementary conversion utilities meta2ddr and ddr2meta are now available in the event files manipulated using previous versions of SAR tools need to be utilized by any of the newly released software.

• Byte addressing standards: Transferring data files between computing environments can introduce compatibility problems due to byte addressing standards.

‘Big-endian’ refers to computing environments in which multi-byte quantities (e.g., long, float, or double data types) are addressed by pointing to their most significant byte. This applies to data stored in computer memory and in files.

For example, a generic binary image data file created on your UNIX system may not be directly imported into a PC-based version of ArcGIS without considering the byte order. The dependency is understood to be CPU-based and not operating system dependent.

ASF SAR tools and the data they manipulate adhere to the IEEE ‘big-endian’ standard. Because the .ddr metadata file has been eliminated, the ‘endian-ness’ checking function has been relocated. When an executable version of a SAR tool is created from source code, the config tool determines the architecture of the host computer. This system value (representing ‘endian’ order) gets stored in the metadata file.

The byte order swapping function, when required, is now added to each tool via the ioline.c function of the asf.a ANSI C library. Byte swapping has not been applied to all SAR tools yet; it will be done incrementally over the next two software releases.

• Software documentation: ASF now provides up to five software documentation outlets for the SAR tools. A UNIX man(ual) page is available at the command line after tool installation, and a more verbose version is published at ASF’s website in HTML/XML and Adobe PDF formats.

Executable versions of most SAR tools offer brief usage guidance from the UNIX command line by typing the tool name followed by no arguments. In select cases, such as with sarview, documentation is provided through a GUI pull-down menu.

In addition, the ASF SAR Tools Software Manual 2003 is available in Adobe PDF format from the website. The manual contains usage, algorithm (equation), and dependency information for every tool. Contact information for each tool has been replaced with the ASF User Services email address (uso@asf.alaska.edu; or see http://www.asf.alaska.edu/).

• Intellectual property considerations: Source code developed by ASF will be distributed either by the Berkeley Standard Distribution (BSD) model or by collaborative agreement. Previous references to GPL (GNU Public License) have been removed from all source code.

• Internet bulletin board support forum: Loosely associated with the February 2004 release is the introduction of a newly created electronic bulletin board resource for SAR tools software support (see https://forum.asf.alaska.edu/). Following a test drive by the ASF User Working Group, the forum is open to the user community. (See the story in this newsletter.)

• SAR tools problem reports: Since the 2002 SAR tools release, a number of known/reported coding errors have been repaired in a number of tools. Where such fixes have successfully graduated from testing, the repaired version of the tool has been included in the February 2004 release.

The remaining repairs (i.e., the backlog) are being performed in priority order based upon customer demand and resource availability. Let ASF know what’s critical to your SAR-dependent projects.

• Future software tool development: The professional staff at ASF are committed to making SAR data more accessible. Efforts are underway to bring the entire suite of tools to the LINUX computing platform. In addition, we are in the process of bundling multiple tools that are commonly used in succession into user-friendly versions.

The Alaska Satellite Facility values guidance from its customers, so please take a moment to provide input the next time you see us at a NASA Earth Sciences booth or when a survey comes across your desk.

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