Joint precision approach and landing system: Difference between revisions

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[[Image:LAAS Architecture.svg|thumb|300px|LAAS architecture, similar in concept to JPALS LDGPS fixed base category]]

TheIn the [[United States Armed Forces]], the '''Jointjoint Precisionprecision Approachapproach and Landinglanding Systemsystem''' ('''JPALS)''') is a military,an all-weather system for precision guidance of landing systemaircraft. It is based on real-time differential correction of the [[Global Positioning System]] (GPS) signal, augmented with a local area correction message, and transmitted to the user via secure means. It is used on terrestrial airfields as well as the [[US Navy]]'s [[amphibious assault ship]]s and [[List of aircraft carriers of the United States Navy|aircraft carriers]] ([[Hull classification symbol|hull classifications]] LH and CVN, respectively).

The onboard receiver compares the current GPS-derived position with the local correction signal, deriving a highly accurate three-dimensional position capable of being used for all-weather approaches via an [[Instrument Landing System]]-style display. Accuracy, while classified, is believed to be about 1 m or better. While JPALS is similar to [[Local Area Augmentation System]], but intended primarily for use by the military, some elements of JPALS may eventually see their way into civilian use to help protect high-value civilian operations against unauthorized signal alteration.

==History==

[[Image:JPALS Tactical Prototype.jpg|250px|thumb|JPALS tactical prototype]]

The development of JPALS was athe result of two main military requirements. First, the military needs an all-service, highly mobile all-weather precision approach system, tailorable to a wide range of environments, from shipboard use to rapid installation at makeshift airfields. Second, they need a robust system that can maintain a high level of reliability in combat operations, particularly in its ability to effectively resist jamming.

==Operation==

JPALS encompasses two main categories: SRGPS (Shipboardshipboard Relativerelative [[GPS]]) and LDGPS (Landland/Locallocal Differentialdifferential GPS). SRGPS provides highly accurate approach positioning for operations aboard ship, including aircraft carriers, helo and STO/VL carriers, and other shipboard operations, primarily helicopter operations.

LDGPS is further divided into three sub-categories: Fixedfixed Basebase, Tacticaltactical, and Specialspecial Missionsmissions. Fixed Basebase is used for ongoing operations at military airfields around the world, while the Tacticaltactical system is portable, designed for relatively short-term, austere airfield operations. The Specialspecial Missionsmissions system is a highly portable system capable of rapid installation and use by [[Specialspecial Forcesforces]].

==Accuracy==

The accuracy of [[Locallocal Areaarea Augmentationaugmentation Systemsystem]] (LAAS) is better than [[Instrument Landing System#ILS categories|CAT III ILS]] accuracy, and will provide horizontal and vertical resolutions of less than 1  m. Although the exact accuracy of JPALS will remain classified, it's estimated that JPALS will meet or exceed this accuracy for authorized users.

==Benefits==

The main benefit of JPALS is that it's a system that can be taken anywhere, anytime, providing a safe and effective way to conduct 24/7, all-weather, anti-jam instrument landing system capability to all authorized users, worldwide. A secondary benefit is a significant reduction in cost over current systems.

The naval version of JPALS transmits a signal that has a low probability of intercept.; Therefore,so it is unlikely that an enemy will detect the signal and trace it back to its source. The existing system, [[Tacticaltactical Airair Navigationnavigation]] (TACAN), is not encrypted or concealed in any way, which can reveal the ___location of the ship on which it is installed. This is not acceptable in [[EMCON|emissions control]] (EMCON) or stealth conditions.

The increase in both accuracy and reliability will significantly enhance operations while reducing non-operational periods due to weather or adversarial efforts.

==See also==

*[[Local Areaarea Augmentationaugmentation Systemsystem]] is a similar system for civilian usage.

*[[Wide Areaarea Augmentationaugmentation Systemsystem]]

*[[Precision approach]]

*[[Instrument landing system]]

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*[[Differential GPS]]

*[[Microwave landing system]]

*[[Electronics_Technician_(United_States_Navy)|Electronics Techniciantechnician]]

==References==

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|url=http://gps.faa.gov/Library/laas-f-text.htm

|title=Local Area Augmentation System (LAAS) Fact Sheet

|work=

|publisher=

|accessdate=November 20, 2005

|archiveurl=https://web.archive.org/web/20060118032723/http://gps.faa.gov/Library/laas-f-text.htm

|archivedate=January 18, 2006

|deadurlurl-status=yesdead

|df=

}}

* {{cite web

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| url=http://www.navcen.uscg.gov/pdf/frp/frp2001/FRP2001.pdf

| title=2001 Federal Radionavigation Plan

| format=PDF

| work=

| publisher=

| accessdate=November 27, 2005

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* [http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/ FAA GPS Programs]

* [http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/laas/ FAA LAAS Fact Sheet]

* [http://waas.stanford.edu/research/jpals.htm Stanford JPALS Page] {{Webarchive|url=https://web.archive.org/web/20060427122246/http://waas.stanford.edu/research/jpals.htm |date=2006-04-27 }}

* [https://web.archive.org/web/20060311054600/http://www.raytheon.com/products/jpals/ Raytheon JPALS Product Page]

* [http://www.fas.org/man/dod-101/sys/ac/equip/jpals.htm FAS JPALS Page]