Format for Interoperability

Written by Peter A. Buxbaum

  THE VALUE OF THE NATIONAL IMAGERY
TRANSMISSION FORMAT, WHICH ALLOWS
GEOSPATIAL IMAGERY TO BE SHARED BY
MULTIPLE SYSTEMS, CONTINUES TO GROW.

Military and intelligence agencies that produce, process, analyze and digest geospatial imagery have implemented a diverse array of geospatial systems over the years in advancement of their missions. For any such system to be authorized for use by a government agency, it must support NITF and be certified as such by the Defense Information Systems Agency’s Joint Interoperability Test Command (JITC).

In that way, data generated by any number of systems can be intelligible and useful to others deployed in a variety of government, military and intelligence organizations.

“The National Imagery Transmission Format is the designated standard for the formatting and exchange of still digital imagery, imagery metadata and imagery-related products between members of the intelligence community,” including the Department of Defense, said Jim Durham, electronics engineer for the National Intelligence Portfolio Branch of the JITC. “Adherence to federal and DoD standards is required before a particular system can be employed in joint or combined operations.”

The National Imagery Transmission Format Standard

Technical Board developed the first iteration of the standard based on available technical information in the late 1980s. The standard continues to evolve in order to accommodate the needs of analysts and other imagery users as well as advances in technology.

Industry, meanwhile, continues to develop and update software that enables users and analysts of geospatial information to exploit NITF data.

“The NITF format was designed with input from DoD and the intelligence community,” said Durham. “The NITF was designed to be a container to transmit or store multiple image arrays, blocks of text, overlaid symbols and annotations, as well as hundreds of different pieces of metadata.”

NITF allows for the storage and dissemination of imagery and its associated metadata—detailed information about the location, context, content and structure of the image—in a single file. By establishing a single standard, NITF is essential to the interoperability of diverse geospatial processing and analytical systems.

“It also means that technology companies can provide standard products for users to work with imagery and have the information necessary available to perform analyses,” said Beau Legeer, director of product management at ITT Visual Information Systems (VIS).

“NITF is an international standard available to anybody to implement in their various software products. Its purpose is to provide a means for diverse systems to share imagery so that they can receive information in a guaranteed standard format with no worry they will lose information and generate an incorrect image because of the format,” Legeer added.

METADATA MINIMUM

NITF mandates a minimum level of metadata to ensure the processing and analysis capabilities of systems exploiting geospatial imagery. “For the imagery to be usable or effective, it needs metadata,” said Durham. “User input and intelligence community requirements have driven the NITF to allow for inclusion of various metadata items. It is up to the community to demand what metadata is important, the creator of the NITF file to include the metadata, and the end-user to have the appropriate software tools on hand.”

In systems that use the standard, NITF functions much like an open-source computer operating system, according to Morgan Welch, engineering manager at BAE Systems for the company’s SOCET GXP product. BAE’s products provide users with the capability to analyze geospatial data with graphical representations such as mapping tools. But NITF is working in the background.

“NITF may be providing the data, but the software provides the user with context,” Welch said. “If the software makes you think about NITF, it is not helping. The heavy lifting should be done internally so users don’t have to think about it too much. Applications that support NITF enable the creation of value-added products based on the same standard.”

Mark Bowersox, a geospatial imagery specialist at ITT VIS, thinks of NITF somewhat differently. “It is more like a file reader that allows interoperability among systems that produce NITF data,” he said. “Without the library of software in our products that reads NITF, users opening a file would not be able to pull the image into the display or to access the metadata to analyze it.”

The specification for NITF Version 1.1, the first operational iteration of the standard, was approved and released by DoD in 1989. JITC activated a test facility designed exclusively for supporting the NITF program in 1990 and completed testing on Version 1.1 in 1993.

NITF has undergone some evolutionary changes since it was first introduced. Version 2.0 was published along with a suite of military standards in June 1993. “The major additions to NITF Version 1.1 included the Tactical Communications Protocol 2 to enable transmission over tactical circuits, improved image compression using the JPEG compression algorithm, support for large images and color images and symbolic annotations using Computer Graphics Metafile,” Durham explained. A number of factors have driven changes made to NITF Version 2.0 in recent years, according to Durham. They included user requirements for improved fusion of imagery, geospatial, and other information and the increased need to share data among DoD, the intelligence community and other systems. Another factor was the strong DoD preference for the selection and implementation of commercial and international standards over government/ military standards where possible. NITF Version 2.1 broadened and internationalized the standardization effort to include input from NATO and other allied nations, national and international standards bodies, and commercial vendors and groups dealing with related standards and technologies.

IMAGE FIDELITY

NITF has grown in importance because the standard has proved to be robust and flexible, and able to handle the complexity and volumes of geospatial data necessary for effective exploitation.

“Most of the other imagery data formats do not allow for multiple image arrays or data blocks in a single file,” Durham explained. NITF, by contrast, allows in a single file inclusion of up to one terabyte of 1,000 arrays as large as 100,000 by 100,000 pixels, over 1,000 symbols, 1,000 blocks of text of 100,000 characters each, and hundreds of metadata items that further describe and define the image array, text or symbols.

Eight different image compression techniques can be used within NITF files. “NITF files can also contain an array that is not an image,” said Durham. “If populated with appropriate metadata values, an NITF file can effectively contain any data that can be stored in an array or matrix.”

NITF does not have any impact on the fidelity and utility of imagery. “It is only a container,” said Durham. “For the most part, the imagery data and metadata can be placed into the NITF format without change. The utility of the imagery is dependent on the choices of the initial creator of the NITF file, how they processed the array, and what metadata they choose to include. Also, the availability of the software tools to the final users of the NITF file must be considered.”

“If you are a NITF-compliant vendor, there is certain level of fidelity you are guaranteed in the image,” said Bowersox. “The image is guaranteed to be viewed as intended by the producer of the data, including the correct geometry and correct placement and display of metadata within the imagery. If the technology is not compliant there is the possibility that the user is not viewing the image as intended.”

ITT VIS’s ENVI product, a platform that allows access, viewing, processing and analysis of imagery and includes automated workflows, supports NITF. The ENVI NITF Module is certified by the JITC to level seven, the highest awarded, and allows reading, writing and displaying all components of the NITF standard file, including image, text and metadata. It also supports NITF’s preferred JPEG 2000 format for reading, writing and disseminating compressed data files, and supports conversions among the three NITF standard versions.

“We have pretty extensive metadata capabilities to better vitalize data,” said Legeer. “We also use analysis and geolocation calculations to view certain fields within the NITF data and to pull out corrupt entities.”

BAE Systems supports NITF with its SOCET GXP platform, a geospatial intelligence tool that uses imagery from commercial, satellite and tactical sources to identify and analyze ground features. Users can automatically measure, annotate, store and retrieve ground features in a series of images to expedite geospatial production, image analysis and map creation. The data can be used to monitor changes over time and coordinate operational missions.

ESRI supports NITF through ArcGIS, an integrated collection of GIS software products for spatial analysis, data management and mapping. “We think of NITF as another data source, and we support it in that way,” said Clark Swinehart, the company’s manager of defense solutions.

“The purpose of NITF is to have the capability to include in a single file structure a variety of information products, including imagery and notes called annotations or markups,” he added. “By being a well-defined published standard, multiple applications can support that specification. That enhances interoperability, as multiple systems can cooperate and interoperate using a file structure like NITF.” COMPLIANCE TESTING

The National Geospatial-Intelligence Agency (NGA) funds the JITC to oversee the NITF Test Evaluation Program, to act as NGA’s executive agent for NITF, and to maintain the expertise needed to conduct NITF standards compliance testing of software implementations and sample NITF products. “Compliance and testing to a published or mandated standard is one of the key steps leading to interoperability among the intelligence community’s imagery implementations,” said Durham.

Software developers, sponsors or NITF file producers approach the JITC and contract for test and certification services. After receiving a description of the item to be tested, its intended use, and the sponsor’s minimum requirements, the JITC can recommend and scope the effort needed to test and certify the product in question, called by JITC an implementation under test (IUT) for compliance with NITF standards.

“At the sponsor’s choice, testing can be performed at the JITC or the developer’s facility,” said Durham. “If testing is done at JITC, it can take place on UNIX, Wintel or Apple operating systems and hardware.”

There are two sides to a NITF compliance test, Durham explained: verifying that the IUT only creates files that are compliant to the NITF, and that the IUT displays imagery contained in compliant NITF files. “Increasingly, sponsors are asking for further evaluation of the IUT with respect to its support for metadata,” said Durham. “Access and proper use of the correct metadata are now being assessed in NITF testing.”

Once analysis of the IUT’s performance is complete, the JITC either registers the IUT as compliant to NITF, or recommends changes to the IUT and schedules retesting at a later date. Those IUTs certified to be compliant are listed on the JITC NITF Test Register Web page. The certification is good for two years.

The JITC certification is also rated at a numerical level from one to seven. At level seven, the system is guaranteed to properly pull metadata and to provide the gamut of processing functionality. Lower levels of certification indicate more rudimentary levels of functionality, such as merely reading and/or writing of NITF data, but without the capability to create full-fledged NITF output.

The NITF standard aids in geospatial processing workflow, according to Swinehart. “If you think of NITF as a bucket containing lots of different things, it makes building image and geospatial products for use downstream in the workflow simpler,” he said. “We used to joke that you can hide your grandmother’s biscuit recipe in NITF. It is a rich specification in that different types of imagery, elevation models, and other data and metadata tags can all be contained in one file. As you build products or workflow you can do all those things in one place. You can generate analysis and include that in the NITF container and pass it along to the next step in the workflow.”

The alternative is performing work piecemeal and generating separate products that have to be passed along individually. “Software products that can use NITF can pass output down the workflow easily, rather than having images pass through multiple data types to continue work,” said Swinehart. “You can put it all into the NITF container and pass it all along.”

Using NITF is likely to continue to get easier. Welch has noticed that some sensor developers are now supporting NITF. Some satellites and unmanned aerial vehicles now distribute data in NITF. “All a user needs is a downlink to view reconnaissance imagery,” he said.

“Digital compression continues to make files smaller so that data can be delivered to smaller platforms,” Welch added. “Advances in hardware are making devices smaller and more powerful. That means that laptops and handheld devices will be able to download and process NITF data. That will enable the distribution of imagery whenever and wherever it is needed.” ♦

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