Displaying multiple maritime video signals
The seas around Norway can be treacherous with storms, deadly cold temperatures, and iceberg threats but they also provide rich fishing grounds for many countries. The Norwegian Coast Guard plays a major role in search and rescue missions and in enforcing national and international fishing laws.
An integrated camera system in a radar-based marine command-and-control system performs optical tracking of selected targets.
By Lawrence J. Curran,Contributing Editor
The seas around Norway can be treacherous with storms, deadly cold temperatures, and iceberg threats but they also provide rich fishing grounds for many countries. The Norwegian Coast Guard plays a major role in search and rescue missions and in enforcing national and international fishing laws. To better carry out its responsibilities, the Norwegian Maritime Service is equipping four of its frigates with advanced command, control, and sensor systems. These systems are being integrated by the Combat Systems Division of EDO Corp. (Chesapeake, VA).
Two displays—primary and secondary—are provided in a multifunction console. A regional map is visible on the primary display. A radar local-area-network access unit also is housed in the base of the console.
A major subsystem incorporated into the four command-and-control systems is a VME-based radar distribution system developed by Primagraphics Ltd. (No. Royston, Herts, England). This subsystem acquires, digitizes, and compresses several radar signals. Then, it transmits them over an asynchronous-transfer-mode (ATM) fiberoptic network for display on two command consoles installed in a Norwegian frigate. The subsystem represents the backbone of a navigational equipment installation that will upgrade the ship's peacetime patrol, search, and rescue capabilities. It also is expected to boost the ship's effectiveness in operating as part of the Royal Norwegian Navy's Surface Combat Force in a conflict situation.
Steve Hill, EDO system development manager for the Norwegian Coast Guard project, stresses that the radar distribution system is part of a full complement of equipment needed to support the command, control, and sensor system for each frigate. Included are a completely integrated combat system featuring new radars, a sonar sensor, a navigation system, an electro-optic sensor, and a helicopter landing system. His company is developing and integrating the various system elements, which will include components from several major Norwegian, European, and US defense suppliers, including Electronicon A.S. (Bergen, Norway), EDO's Norwegian partner.
The electro-optic sensor or camera system performs optical tracking that allows an operator to position infrared (IR) and television (TV) cameras on targets of interest. In addition, a laser rangefinder is used to track targets by using the TV camera linked to a ballistic-control computer, which, in turn, can deliver a weapon-firing solution, if necessary.
The radar is an AN/SPS-67 (V3) from DRS Technologies' Advanced Programs Inc. (Columbia, MD). The sonar is an advanced fish-finder type provided by the Simrad unit of the Kongsberg Group's Kongsberg Maritime A.S. (Horten, Norway). An integrated bridge system to assist in navigation and propulsion monitoring comes from Norcontrol IT A.S. (Horten, Norway), which is also part of the Kongsberg Group.
EDO has contracted with Electronicon to build the multifunction consoles (MFCs), and Primagraphics supplies the local-area-network (LAN) access units (see figure below). According to Hill, these integrated elements are "the command and control heart of the ship." The MFC houses a workstation built around a Hewlett-Packard (Palo Alto, CA) HP744 VME board computer. The workstation also incorporates disk drives, interchangeable displays, and Primagraphics hardware.
The LAN access units and MFCs enable the data from the various sensors (radars, sonar, GPS, gyro system, and IFF target extractor) to flow into the ATM tactical network for processing and display. Andrew Haylett, project manager at Primagraphics for the EDO program, says his company's contribution includes a mix of Primagraphics and third-party hardware and software.
The overall task requires digitizing and compressing radar video signals from four radars, which are supported by four video servers, then distributing all the video signals over the ATM network to two MFCs. Haylett says, "It presents a multiwindow, multiradar display with graphics and TV video."
The LAN access units use Primagraphics Virgo++ radar interface cards that forward digitized radar data through a Jaguar polar store card to the CAT-based radar compression engine. (CAT is Primagraphics' code name for the Texas Instruments TMS320C80 DSP chips used in the compression/decompression engines.) Four radar video streams are compressed by this engine and transferred over the ATM network by a PowerPC host processor in the ATM interface unit.
The distributed architecture for the radar system partitions into two equipment sections or columns. The left column headed by the radar input unit represents one radar LAN access unit, and the right column represents a single multifunction console. Analog radar inputs are digitized by the Virgo++ boards and stored in the Polar store unit in relation to the azimuth of the antenna sweep. The CVAT compression unit condenses the digitized signals for placement on the VME bus and for asynchronous-transfer-mode formatting. In the right equipment column, the PowerPC receiver unit moves the compressed digital stream to the bus and the CAT radar compression engine. After scan conversion and formatting, the data are displayed as range and bearing data.
The display consoles accept the ATM data stream and recover the original radar polar-store. The CAT-based radar decompression engine outputs the polar data to the Vantage II radar scan converter, which supports a multiradar, multiwindow display. The output of the Vantage scan converter is displayed in the CAT-based image-display system, which combines the radar picture with an X-Window graphics display supporting underlay and overlay graphics. The Leopard TV frame grabber on the CAT provides the additional ability to acquire two channels of NTSC or PAL video signals from the TV camera. "The HP744 serves as the overall system controller and also supports the second screen of the dual-screen X-Window display," Haylett adds.
EDO's Hill points out that the radar distribution system is the critical component of each MFC, "which allows us to bring TV camera video to the Leopard frame grabber, while the [Vantage II] scan converter brings in the radar video." He adds that the radar distribution system "is unique in that Primagraphics uses distributed radar video instead of more complex discrete processor boxes. They're able to compress the radar video at the source, send the data over the ATM network to be decompressed at the MFC workstation, and then fed to the front end of the scan converter."
In the Primagraphics radar distribution system, the LAN access unit includes the front-end Virgo radar-interface boards, which digitize the analog signals from each radar sensor and synchronize them in relation to their azimuth on the antenna's sweep. A digital interface moves the signals to the Primagraphics Jaguar polar store board, which serves as a RAM-based memory for storing the signals as they occur in azimuth and builds an image based on a complete revolution of the antenna.
In the CAT radar-compression engine, the TMS320C80 digital-signal processor takes the digital radar stream from the Jaguar polar store card and performs a lossless compression on each line of data. Then, it makes the compressed radar stream available upon demand across the VME bus. Each CAT-based engine can process four radar streams.
A PowerPC 750-based single-board computer from Cetia S.A. (Toulon, France) backed by a Cetia daughterboard provides the ATM interface, which packages the data in TCP/IP format for transmission over the bus. The daughterboard carries optical drivers for the receiver/transmitter, with the optical fiber plugging into the front end of the card and the output feeding the system's ATM switch. Haylett says Cetia also provides the board-support software for the signaling function to move data. He also points out that the entire sequence — from analog radar reception through the Virgo, Jaguar, and CAT compression - takes place several thousand times per second.
All the data are routed through the central ATM switch—a four-port unit from Fore Systems (San Jose, CA) that supports two radar access units and two MFC units. A network interface at each port switches data packets for distribution as they are received.
Servicing the MFC
A key section of the radar distribution system is a card set, with the signal flow beginning at the receiver/transmitter of that section's ATM interface. The PowerPC in the interface moves the compressed digital stream to the bus and the CAT radar decompression engine, where the DSP decompresses and processes the stream before scan conversion takes place.
Scan conversion in the Vantage II enables the signal to be presented—after formatting in the display controller—as range and bearing data in proper x-y format on the MFC's primary LCD panel display. This display is used primarily for showing tactical information; the secondary display is usually reserved for presenting administrative information, which also includes helicopter status information.
The Leopard card is not part of the radar distribution system. Its purpose is to process PAL or NTSC inputs from the EDO command, control, and sensor system's TV camera for display.
The radar distribution system uses an enhanced version of Primagraphics' Advanced Radar Interface Software (PARIS) suite to control the local and remote equipment cards. Haylett says that by using a distributed architecture based on the company's recently introduced compression and decompression package, the system can display scan-converted data from the four radars on each console. This software also enables the use of video windows and overlay and underlay graphics.
Primagraphics has delivered three ship sets of the radar-distribution system to EDO, with a fourth to be delivered soon. EDO is integrating the multiple systems and developing system software. Hill says EDO has had no difficulty integrating Primagraphics' products into the workstations. "It's early in the program, and things are going smoothly," he reports, "but there are always software challenges."
Initial land testing of the overall command, control, and sensor systems is scheduled to begin this month in Norway, and plans call for outfitting the first frigate in the first quarter of 2001.
DRS Technologies Inc.
Columbia, MD 21046
Chesapeake, VA 23320
Fore Systems Inc.
San Jose, CA 95134
Norcontrol IT A.S.
No. Royston, Herts SG8 0SS, England