Home Articles GPS: A military perspective

GPS: A military perspective

Rajat Baijal
Rajat Baijal

Manoj K. Arora
Manoj K. Arora
Department of Civil
Engineering IIT Roorkee
Roorkee 247 667
[email protected]

Abstract
Accurate and todate information on the location of enemy and own forces is one of the most critical information a military commander seeks. In today’s fast paced electronic battlefield such information if disseminated timely can act as a major force multiplier. The dawn of the space age has led to the development of several dual use technologies, which find extensive application both in military and civilian fields. Global Positioning System (GPS) is one such technology. Military forces the world over are using GPS for diverse applications both during wartime and peacetime. These include navigation, targeting, rescue, guidance and facility management. With war clouds looming over west Asia, the US led forces are likely to showcase weapon systems, which rely heavily upon GPS for their accuracy and lethality. In this paper, some applications where GPS can be used effectively by the armed forces, have been highlighted.

Introduction
Human beings have always looked towards the skies for navigation. Till today celestial bodies like sun and stars are used for finding out the directions. This assumes more importance if you are a soldier moving in unknown enemy territory. The significance of locating one’s position in the world cannot be more important than for a soldier, as this could mean the difference between life and death, defeat and victory.

With the coming in of the space age, mankind has tried to replace these celestial bodies with artificial satellites so that navigation is possible both during day and night. Global Positioning System (GPS) is one such dual use technology, which has found extensive application both for military and civilian purposes in area of navigation and others. GPS has given military forces the lethal combination of precision strike with adverse weather performance, standoff range, and operational flexibility – all at a low marginal cost (Hasik, 2001).

Origin of GPS
The Navigation Satellite Timing And Ranging (NAVSTAR) GPS was developed by the US Department of Defense (DoD) as a worldwide navigational and positioning resource both for military and civilian uses. The system is based on a constellation of twenty-four satellites in six orbits (Fig 1) acting as reference points for receivers on ground (Hurn, 1993).

Requirements of a Good Navigation System for Military
The basic needs of any armed forces as far as a good navigation system is concerned can be enumerated as below.

  • Accurate
  • All Weather
  • Easy to use
  • Portable

The GPS system currently in service meets these requirements fully except for the fact that ultimately it is a system run for the US military and if you happen to be their adversary then you may be in some problem as the power to introduce intentional error in the signal rests with them. Although the US DoD’s policy of “Selective Availability” (under which intentional noise was added to GPS signals to make them less accurate) has been removed last year, its reintroduction is still in their hands.

Accuracy of GPS may vary from few meters to few tens of meters, which meets the military needs for navigational purposes. However, for precise location of targets for aerial bombings, missile strike etc accuracy to a level of mm is required. This can be achieved through Differential GPS (DGPS). Nevertheless to achieve this level of accuracy, proper error modeling is necessary. A detailed discussion on GPS related errors and accuracy may be found in Tiwari et al. (2000).

Further, the GPS satellite signals are also not affected to that extent due to bad weather as conventional terrestrial radio signals. This is an important requirement, as military forces need all weather navigation systems.

Most of today’s GPS receivers are quite easy to use and give the position in both the geographical latitude and longitude and the local map projection system coordinates besides providing data in WGS-84 coordinate system. Moreover over the years, the GPS receivers have also drastically reduced in size and weight, and thus become more portable. For example, today wristwatches commercially available off the shelf have GPS receivers built in them.

Fig.1: Image showing orbits of various GPS satellites
(Source:

Military Applications of GPS
The role of the military in any country can be very varied and every system for it must meet these requirements fully. In general, there are two major tasks of the military vis Barrack and the Battlefield. Barrack encompasses all the peacetime activities in which the military personnel are involved. This may include training, disaster relief, peacekeeping and management of large bases / installations. Battlefield includes all wartime activities. The military applications of GPS revolve around these activities. Some of these can be enumerated as,

  • Navigation
  • Tracking
  • Bomb and Missile guidance
  • Rescue
  • Facility Management
  • Map updation

These are only some of the applications as more and more uses may be derived from GPS.

Navigation
For a soldier operating under cover of darkness in enemy territory the biggest challenge is navigation due to unfamiliar territory and lack of easily identifiable landmarks on ground. Soldiers have been using night skies for ages to find out direction but their location on ground cannot be determined. The necessity of knowing their own position by troops during war was very clearly highlighted during the Gulf War (1990) and the Kargil conflict (1999). This can be judged from the fact that initially about 1000 GPS receivers were issued for use during the Gulf war but by the end nearly 9000 handheld devices were in use (Fig 2). Similarly, during the Kargil conflict, Indian patrols operating in rugged terrain along the line of control, initially strayed into enemy held areas with disastrous consequences but later on the availability of handheld GPS receivers proved to be invaluable to them. In fact, these GPS receivers are fast replacing the conventional compasses in a soldiers rug sack. Special forces and crack teams also use these to reach and destroy vital enemy installations. Such teams can draw air and artillery fire accurately by providing the accurate positional data. Further, gun positions can be occupied quickly using GPS, as in modern warfare, artillery batteries must move often to keep pace with assault troops and to avoid being hit by counter fire. Convoy movements can also be tracked and planned effectively using GPS devices.

Tracking
In a military scenario, potential targets need to be constantly tracked before they are declared hostile and engaged by various weapon systems. This tracking data is fed as input to modern weapon systems such as missiles and smart bombs etc. Just to site an example, the US Army has developed a GPS Truth Data Acquisition, Recording, and Display System (TDARDS). It is a compact, lightweight, low-cost, and easily transportable or mobile GPS-based tracking system that uses up-to-date GPS data, radio data link, and computer technology to provide highly accurate, real-time time-space position information (TSPI) on up to ten test objects, such as ground vehicles, helicopters, and fixed-wing aircraft. The system is highly modular, built with commercial off-the-shelf hardware, and easily modifiable to meet any special needs of individual testing and tracking applications (Gilkey et al., 1994).

Bomb and Missile guidance
Modern day weapon systems are designed to use GPS data as input for targeting and guidance. Cruise missiles commonly used by US to accurately hit targets from large standoff distances use multichannel GPS receivers to accurately determine their location constantly while in flight. The Multiple Launched Rocket System (MLRS) vehicle uses GPS based inertial guidance to position itself and aim the launch box at the target in a very short time (Fig 3). This reduces the chances of detection and counter bombardment. The Exploitation of DGPS for Guidance Enhancement (EDGE) program of the US army has developed a 2000 lb glide bomb, which uses a GPS seeker rather than a Laser for guidance. This bomb could accurately hit its target 11 miles from its drop point guided by four DGPS base stations about 1000 nautical miles away (Anonymous(a), 2001).

Rescue
Rescue and emergency response is another area where GPS can prove invaluable to the military. Determining the location of a casualty during operations, emergency response teams can use the GPS to reduce response time. For example, the US Air Force is already taking advantage of GPS based technology and is developing a Combat Survivor Evader Locator (CSEL) system. The new system integrates the GPS receiver with a communications radio so that search and rescue teams can locate downed aircrew members faster and more accurately than before (Anonymous(b), 2001).

Map Updation
To carry out planning at various military headquarter levels, the defence forces need accurate and updated maps at various scales

Fig. 2 : Image showing use of GPS receivers by US soldiers during Gulf War
(Source: https://www.aero.org/publications/GPSPRIMER)

depending upon the level of the commander for planning operations, administrative planning and training. The availability of GPS shall augment the collection of precise data necessary for quick and accurate map updation. The GPS can also be used effectively for the establishment of grid control locations for the placement of various weapons and other assets, location of targets etc. For example, the modern mapping techniques such as remote sensing and GIS will now constantly use the DGPS technology to register the images into absolute geocoordinates (Kelly, 2001). This would enable the military personnel to utilize modern map products to accurately determine the locations of target points for use by the new generation of weapons.

Fig.3: Image showing Multiple Launched Rocket System
(Source: https://www.aero.org/publications/GPSPRIMER/)

Facility Management
In almost all countries of the world, the military manages and operates large bases which cover extensive areas. To manage these facilities effectively, it is essential to prepare an accurate base map. Here GPS/DGPS can be of immense help, as existing maps are not updated regularly. GPS co-opted with Geographic Information System (GIS) can effectively tackle this task. For example, at Yokosuka US Naval Base in Japan, Arc View GIS software was used to evaluate three different components for the GPS implementation. First, for modeling the optimum location for a GPS base station, secondly for selecting benchmark locations to fix the base station location and thirdly evaluating accuracy of survey by GPS (Dunham, 1999).

Conclusions
With war clouds looming large over the west Asian region, the world is likely to witness the state of the art weaponry being used by the US led forces. Most of these, either directly or indirectly shall be using GPS to accurately target and achieve the desired results. This paper has demonstrated the capabilities of GPS receivers for various kinds of military activities both during war and peace. Depending upon the nature of activity (i.e., navigation or precise target location), a particular kind of GPS may be used. It may thus be summarized that the GPS based weapon systems are here to stay and will form the backbone for the future development of better, more accurate and lethal munitions.

References

  • Anonymous(a), 2001,
  • l Anonymous(b), 2001, GPS use Extended to the world, https://www.af.mil/news/.
  • Dunham Dale, 1999, Military Base Planning Using GIS and 3D Modeling, https://www.gis-services.com/
  • Gilkey J, Galijan R, Palomino A, 1994, The Army GPS Truth Data Acquisition, Recording, and Display System (TDARDS) at the White Sands Missile Range (WSMR),
  • Hasik J.M, 2001, GPS at War:A Ten-Year Retrospective, Michigan State University USA
  • Hurn Jeff, 1993, Differential GPS Explained, Trimble Navigation Ltd USA.
  • Kelly J, Bogensberger E, Heitz S, Beckman K, Emery J, Rambo J, 2001, Development of the first Military GPS Handheld Survey System: Initial Report. Rockwell Collins Government Systems USA.
  • Tiwari R.S, Arora M.K, Kumar Amit, 2000, An Appraisal of GPS related Errors, [email protected], 4, 37-40.