LAAS architecture, similar in concept to JPALS LDGPS fixed base category
The Joint Precision Approach and Landing System (JPALS) is a military, all-weather landing system 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. 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. 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.
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JPALS tactical prototype
The development of JPALS was a 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.
JPALS encompasses two main categories: SRGPS (Shipboard Relative GPS) and LDGPS (Land/Local Differential 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: Fixed Base, Tactical, and Special Missions. Fixed Base is used for ongoing operations at military airfields around the world, while the Tactical system is portable, designed for relatively short-term, austere airfield operations. The Special Missions system is a highly portable system capable of rapid installation and use by Special Forces.
The accuracy of Local Area Augmentation System (LAAS) is better than 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.