Improved GPS receiver provides increased benefits to warfighters

Air Force Space Command News Service

The Navstar GPS Joint Program Office pioneered Global Position Systems more than 11 years ago with its PLGR - Precision Lightweight GPS Receiver. At the time, PLGR was "state-of-the-art," providing warfighters with position, velocity, navigation and time.

Now the Joint Program Office has improved upon its original GPS and is prepared to field the Defense Advanced GPS Receiver. DAGR will give the warfighter a number of improvements over PLGR, to include many capabilities not found on any commercial receiver.

Whereas PLGR is large and weighs 2.75 pounds, DAGR is just under one pound and fits easily into a battle dress uniform pocket or a standard ammo pouch. The external antenna on PLGR, and on many commercial receivers, is always in the way and is the source of most maintenance problems. DAGR's antenna is internal.

PLGR requires the large and expensive BA5800, military-only, battery at a cost of $25.13, or eight AA batteries, which last only 13 hours under continuous use. DAGR, however, operates on only 4 AA batteries, that last 19 hours under continuous use or for up to 200 hours obtaining four "fixes" per hour. Life cycle expenses are the greatest part of all military equipment costs. With the much lower cost of batteries, operating DAGR will be much more economical throughout its expected life of operation. Additionally, expected repairs, known as Mean Time Between Failure, are much lower for DAGR.

Both PLGR and DAGR can give accurate direction while on the move or when tracking satellites. However, DAGR also offers a magnetic compass. Both receivers can store up to 999 Way Points, which can be used for route planning, targeting or situational awareness.

PLGR uses four single channel satellite signals to compute its PVNT solution and state-of-the-art commercial receivers use "all in view," which is up to 12 single channel satellite signals, while DAGR uses up to 12 dual channel, two frequencies, satellite signals. DAGR is far more accurate, correcting sources of error known as Doppler, multipath, ionospheric bending and ambient noise.

Perhaps the most important improvement over PLGR and commercial receivers is DAGR's Selective Availability Anti-Spoofing Module. This module allows DAGR to be securely encrypted without the risk that unfriendly forces could capture a DAGR and discover its encryption code. Additionally, while commercial receivers use only Standard Positioning System, DAGR uses Precise Positioning System, which is much more accurate. If satellite signals are jammed, commercial receivers will be unable to receive and decode the signals, while DAGR will continue to operate through a considerable amount of jamming. Enemy forces may also be able to rebroadcast a satellite signal at a higher level. This signal, known as spoofing, gives a false location. Commercial receivers and PLGR are not able to detect that a signal, if being spoofed, will calculate incorrect PVNT. However, DAGR will detect the spoofed signal and will reject it, while continuing to provide highly accurate navigational information.

While PLGR has a simple textual-based screen, DAGR uses a modern Graphical User Interface, which is menu driven. It provides numerous graphics, which aid in situational awareness and ease of use. DAGR can use a wide variety of maps, which can be downloaded from a computer. Additionally, information, mission planning and reprogramming can be performed from one DAGR to another or from PLGR to DAGR by using available cables.

DAGR was designed to be backward compatible with PLGR. Wherever a PLGR has been integrated into a vehicle or weapons system, it can be replaced by DAGR without modification to the vehicle or weapons system. In fact, the mount for DAGR will fit the same hole pattern as the PLGR mount. All data and power cables, as well as antennas, mounts and other accessories for DAGR are available.

DAGR was also designed for special military requirements, such as integration with Laser Range Finders. An LRF will tell you how far away a distant object or target is and its direction - but when attached to DAGR, DAGR will give you the instantaneous location of any target within the range of the LRF, as well as the distance and direction. DAGR was also designed to enhance the emplacement of weapons systems, known as "Gun Laying."

DAGR is smaller, lighter and cheaper than PLGR. It has far more capabilities and is more accurate and reliable than PLGR or commercial receivers. DAGR is the right answer for today's and tomorrow's warfighter, bringing highly reliable position, velocity, navigation and time to handheld users, weapons systems and vehicles.

In November 2004, the Army plans to begin New Equipment Training and fielding DAGR to Special Operations Units.