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GPS - The different arguments..?
Age of JDAM Technology
'JDAM' (Joint Direct Attack Munition), is equipment that turns a simple iron bomb or so-called dumb bomb into a satellite-guided weapon capable of falling within 10 feet of its target.2 It extensively uses GPS to help pinpoint locations anywhere on Earth and at anytime. The Pentagon, the topmost defense authority of the U.S confirmed that JDAMs have been used in the opening phase of operation against worldwide terrorism in Afghanistan. The functioning of JDAM using GPS technology is interesting. The $19,000 (approximate) worth JDAM contains a miniature size GPS receiver and can be programmed with the exact coordinates (latitude, longitude and altitude) of an intended target. Once freed from the aircraft, a JDAM collects data from the GPS satellites to position where the bomb is, relative to the target coordinates. The tail of 'JDAM' also contains small control fins that regulate and direct it as it falls.  U.S F/A-18 dropping JDAM guided bomb3 Source: BBC The successful strike of JDAMs, mainly depends on the accurate set of pre-programmed co-ordinates in it. Hence, due to inaccurate coordinate programming by the pilots, the bombs still miss their targets. The US military uses the WGS co-ordinates, similar to the latitude and longitude shown on maps. The accurate co-ordinates of the target have to be loaded into a GPS-guided weapon and as a result there are chances of 'human error' in manipulating the coordinates. Also, in practice, errors of more than 10m can creep in, due to atmospheric conditions and electronic "noise". If a GPS-guided weapon loses touch with the guiding satellite signals, it falls back on inertial navigation - calculating where it is, in relation to its last fixed position. If that happens with a JDAM, its "circular error probable" rises to 30 m (98 ft).6 The errant JDAM-guided missile launched by American B-2 stealth bombers struck the Chinese Embassy in Belgrade, Yugoslavia on 7 May 1999, killed three people. Their target was supposed to have been a Yugoslav arms procurement office. The mistake was put down due to faulty map data. Also, during the strike against Afghanistan, the US Navy jet dropped a 2,000lb (900-kg) JDAM in a residential area near Kabul airport in Afghanistan instead of the intended 'military helicopter', which is about a kilometer-and-a-half away.6 It was reported that the accident occurred from a targeting process error. Dithering and Jamming GPS Signals GPS is considered as a dominant global standard satellite navigation and U.S. policy makes both the GPS signal and the receiver design specification as an open standard and completely free of charge to the public. This lack of restriction results in the complimentary usage of GPS devices, as there are no controls on who can build/buy a GPS receiver. It is suspected that the terrorists attempted to use GPS technology built by the U.S, against the US itself. Hence, as the GPS signals from the satellites are freely available all over the planet, the U.S is willing to do 'selective deniability' to degrade GPS quality on a regional basis. Evidence confirms that there is a significant dithering of the GPS signals over Afghanistan and other areas where there are military operations. This created a buzz in the GPS industry worldwide, over the stringent policy action on GPS and the possible return of SA by the U.S. However, on Sept. 17, 2001, the Interagency GPS Executive Board, which governs the system, posted a statement on its Web site by saying 'SA" will never be reinstated. As JDAMs mainly rely on satellite signals, enemies could develop a jammer that would spoof the GPS signals. On the other hand, the U.S military is trying to 'jam' GPS signals to avoid misuse by terrorists. The Pentagon has developed the capability to jam civilian GPS signals within a specific targeted area and could easily deny the 36-meter-accuracy civilian signal to the Taliban forces, without interfering with users in other areas of the world. Depending on whether the Pentagon, which developed and operates the 28-satellite GPS constellation - uses airborne or ground jammers - this could deny the signal to the Taliban over a wide area, with some of the jamming potentially spilling over neighboring nations like Pakistan and Uzbekistan. Hence, a new "navigational war" is here to stay, in which forces play a cat-and-mouse game of trying to jam each other's ability to receive GPS signals, and also counteract jamming attempts made by others.4 Epilogue The world is fast moving ahead, with day-to-day technological advancements. At the same time, terrorism is threatening humanity using the same technologies. The suspicion of destructive usage of GPS technology against the U.S is an inopportune one. Though the U.S declared that it would not restore the SA, it would not be surprising if the US turns the entire system off! However the affirmation given by U.S of not reinstating SA again ensures us that there is no such serious issue being contemplated around. If we backtrack in history, it is the Pentagon that allotted millions of dollars in the research and development of smart GPS guided bombs to hit the specified target with higher accuracy. This was due to the poor performance of first phase of GPS guided weapons during Gulf War and failure of laser guided bombs due to bad weather during Kosova conflict. The supplementary issue of removal of SA will explode this technology to public with much more simplicity. Necessary steps have to be taken for the effective usage of GPS and stringent rules have to be made to keep away this technology from terrorists. There could be different accuracy limits and restrictions, depending on the end use of GPS. Also it is definitely the need of the hour to prepare a proper 'code of conduct' even for the military use of GPS, by involving worldwide GPS communities. It will serve to create security and confidentiality for the geo-spatial community, ensuring constructive usage of GPS technology for a better tomorrow. References:
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