Lost no more: the hand-held Global Positioning System receiver is the foundation of situational awareness for dismounted soldiers in today's military operations.

A Boeing Delta II launch vehicle successfully delivered to orbit a replenishment Lockheed Martin Block IIR Global Positioning System (GPS) satellite for the US Air Force on 17 November 2006. It was the third of the modernised GPS IIR-16 (M) satellites that feature greater accuracy and increased resistance to interference. The 29 active satellites in the GPS constellation are spaced in orbit so that at any time a minimum of six satellites will be in view to users anywhere in the world.

In simple terms the Navstar GPS constellation provides accurate position, navigation and timing (PNT) information 24 hours a day under all weather conditions. Rarely has military technology become so important to both the military and civilian communities so quickly. The first constellation, which achieved full operational capability in July 1994, enables time be measured to within one millionth of a second, velocity within a fraction of a kilometre-per-second and location to within 30 metres. Commercial GPS receivers use the Standard Positioning Service (SPS) while military GPS receivers, with crypto keys, can access the Precise Positioning Service (PPS) to provide a more accurate positional 'fix'. In December 2006 the US Air Force awarded Boeing and Lockheed Martin $ 50 million contracts to complete System Design Reviews by March for the next-generation GPS Space Segment program, also known as GPS Block III. The GPS Wing, Space and Missile Systems Center, Los Angeles Air Force Base, California is expected to award a multi-billion dollar development contract later this year. The full constellation of GPS III satellites will have 500 times the transmitter power of current satellites, thus making it much more resistant to enemy jamming and real-time accuracy is expected to be one metre. A new military-only signal (M-code) on the L1 and L2 links will be ready by 2010 and a new civil signal will be added to the L2 link and a new civil-only L5 link will be introduced.

The old joke that there is nothing more dangerous on the battlefield than a second lieutenant with a map hints at the difficulty of accurate map reading, especially at night and in close terrain. The use of GPS answers the question of << Where am I? >> and when 'networked' by radio can answer the question of << Where are my friends? >> Used in conjunction with a laser rangefinder the GPS can be used to accurately determine the position of an enemy, once the usually difficult task of locating the enemy has been accomplished. These three pieces of information are the basis of situational awareness and allow precision strike.

The most widely used hand-held GPS receiver is the AN/PSN-11 Precision Lightweight GPS Receiver (PLGR) developed by Rockwell Collins Government Systems for the US Department of Defense. The PLGR is a ruggedised, five-channel, single-frequency GPS receiver originally designed to be used in the handheld mode by ground mobile and airborne troops. Standardised interfaces enable the PLGR to provide PNT information to a wide variety of vehicles, weapon systems and host platforms, including integrated applications. The PLGR can store up to 999 waypoints for route planning. The PLGR measures 24.13 x 10.41 x 6.60 cm and weighs 1.25 kg with batteries fitted. The PLGR requires the large and expensive military BA5800 battery or eight AA batteries, which provide only 13 hours of continuous use. The enhanced AN/PSN-11(V) version can be integrated with a laser rangefinder. Rockwell Collins initially produced PLGRs for the Department of Defense with a six-year warranty but this was later extended to ten years.

Since the first production contract in March 1993 Rockwell Collins has produced more than 200,000 units for US customers, including 112,819 units for the US Army and allied nations. Initial production was supplanted in 1996 with an enhanced version (PLGR+96) that provided improved computer memory and reduced power consumption. Although production for the army ceased in fiscal year 2005 a programme to upgrade the initial version to PLGR+96 software continues as these systems are passed to lower readiness Force Package 4 units. The US Army's Project Manger (PM) GPS states, << [the] PLGR may not have the 'bells and whistles' of the latest commercial GPS receiver designs but testing demonstrates PLGR outperforms commercial models especially under any form of intentional or accidental signal interference. PLGR is a proven rugged reliable receiver and will remain a part of the total Army GPS solution for years to come >>.

The US Army began fielding the Rockwell Collins AN/PSN-13 Defense Advanced GPS Receiver (Dagr) in November 2004 to replace the PLGR. According to the manufacturer the handheld Dagr, << incorporates five times the capabilities and functions of the PLGR while reducing the overall size, weight and power requirements >>. The Dagr is a twelve-channel, dual-frequency, continuously tracking GPS receiver which uses the latest technology including 'All in View' satellite tracking and the Selective Availability Anti-Spoof Module (Saasm) to access the Precise Positioning Service (PPS) signal. The Dagr, as with the PLGR, can store 999 waypoints. The Dagr measures 8.78 x 16.12 x 4.00 cm and weighs .43 kg with batteries. It offers much lower life cycle costs, as it only requires four AA batteries, which last 19 hours under continuous use. The battery life of both the PLGR and Dagr can be extended by only turning on the receiver when the user requires a positional 'fix'; if used to provide four fixes per hour the Dagr's four batteries will last up to 200 hours. Unlike the receiver it replaces the Dagr also offers a magnetic compass.

The Dagr was designed to be backward compatible with the PLGR so that wherever a PLGR has been integrated into a vehicle or weapon system it can be replaced by a Dagr with no modification required. Information, mission planning and reprogramming can be entered into one Dagr and then transmitted to another Dagr or PLGR by cable.

Unlike the PLGR, which has a simple textual-based screen, the Dagr uses a modern menu-driven Graphical User Interface. The US Army Corps of Engineers Topographic Engineering Center (Tec) at Fort Belvoir, Virginia is creating maps, available in different scales, which can be downloaded to computers and then transferred to the Dagr. The software in the Dagr Map Toolkit Loader converts the Tec map files into GPS map files. Although these are not high-resolution colour maps they are an improvement over what was previously available and is a further step in the development of high-resolution maps for GPS receivers. A map software product called GPS Map Creator is available for organisations wanting to create maps.

Rockwell Collins received an $ 82.7 million firm-fixed-price and cost-plus-fixed fee contract modification in November 2006 exercising production options for 37,787 Dagrs and accessories. These will be delivered by October 2008. Rockwell Collins has produced almost 125,000 systems for the Department of Defense and allied nations. A $ 62,589,087 firm-fixed-price and cost-plus-fixed fee contract modification, awarded in August 2006, covered 28,054 Dagrs to support Foreign Military Sales to Australia, Bahrain, Canada, the Czech Republic, France, Germany and Britain with work scheduled for completion this June.

The US Army's Project Manger (PM) GPS has nine GPS New Equipment Training (Net) teams which provide 'train the trainer' courses to unit instructors. After training instructors from the 1st Infantry Division one Net team reported last year, << The increased satellite coverage, user-friendly software similar to Windows, intuitive menu system, reduced size and weight and increased anti-jamming/spoofing capabilities were all points of interest and praise >>. PM GPS anticipates an accelerated pace of fielding and training to meet the service's goal of over 235,000 Dagrs in service by 2013.

Rockwell Collins developed the Ground-Based GPS Receiver Applications Module (GB-Gram) in parallel with the Dagr as an embeddable lightweight GPS receiver. Weighing 100 grams the GB-Gram has the full functionality and capabilities of the Dagr and can be integrated into a wide variety of command, control, communications and computer systems.

The GB-Gram is incorporated into the Commander's Digital Assistant (CDA), a key command and control tool of the US Army's development Land Warrior. The service's Program Executive Officer Soldier describes CDA Version 5 as an integrated, ruggedised computer with satellite communications, military GPS-GB-Gram, interface to terrestrial radios, 40 GB hard disk, 6.5-inch sunlight readable screen and Force XXI Battle Command, Brigade-and-Below (FBCB2) battle command software. The initial prototypes of the CDA were produced in 2002 in two configurations; the first is the CDA-Handheld based on the commercial iPAQ 3975 personal digital assistant and, secondly, the CDA-Tablet, which is based on the Panasonic CF-34 notebook computer. PEO Soldier and General Dynamics C4 Systems, prime contractor for the Land Warrior programme, decided to develop a single system with a screen midway in size between the two initial versions following feedback from users of a small number of prototypes used for field trials in Iraq in 2003. Although the army had considered spiralling the CDA into service as part of a Dismounted Battle Command System it has now decided to field it as part of the complete Land Warrior ensemble with the Stryker Brigade Combat Teams, equipped with the General Dynamics Land Systems Stryker 8 x 8 armoured vehicle. The CDA Version 6, now under development, will consist of two primary modules; a ruggedised computer and a communications module that incorporates satellite communications, GB-Gram, antenna and interfaces.

The 3rd Battalion, 25th Marine Regiment became the first US Marine Corps unit to use the new AN/PSC-13 Dismounted Data Automated Communication Terminal (D-Dact) on operations when it was equipped with the system in mid-2005. The D-Dact and the M-Dact (Mounted) provide command and control capabilities for commanders from platoon to battalion level. The M-Dact is also described as the service's blue force 'tracking program of record'. The D-Dact, which weighs 879 gr, consists of a rugged personal digital assistant (R-PDA), command and control CE (C2CE) software, an interface with the Sincgars, GB-Gram and a TacLink 3000 tactical modem. The R-PDA incorporates a 400 MHz processor, a 2 GB digital memory card for map date and 128 MB of random access memory. The GPS indicates the user's position on a moving map display. As with commercial PDAs, commanders enter information by touching the screen with a stylus and enjoy the tactical advantage of not having to use voice communications to relay the information of other users on the network. The D-Dact with its touchscreen monitor is powered by AA lithium batteries, which allow from eight to 16 hours of continuous use.

Under the supervision of the Marine Corps Systems Command the Dact team includes Tallahassee Technologies, which, designed and produces the R-PDA for the D-Dact and the rugged hand-held computer for the M-Dact, Northrop Grumman, which developed the command and control PC and CE software applications and Raytheon, which provides system engineering/integration support and furnishes the TacLink modem.

The final report of the 2004 Joint Warrior Interoperability Demonstration, which was based on a homeland security scenario, noted, << D-Dact's unique ability to display, in real-time, all first responder positional data on a Cop [common operational picture] on their own hand-held PDA with positional information updated every 60 seconds, makes this tool especially valuable for command and control in a crisis/emergency situation. In addition, the trial was successful in providing wireless text chat functionality for communications among first responders and higher authorities as well as the ability to send and receive reports either using a free-text mode or a pre-loaded standard report format. >>