European Geostationary Navigation Overlay Service (EGNOS) - better than 2 meter accuracy
Wide Area Augmentation System (WAAS) - 1.0 metre laterally and 1.5 metres vertically
Multi-functional Satellite Augmentation System (MSAS) - Japan - 1.5-2 metres horizontally and laterally
GPS Correction - 1.5-2 meters
Local Area Augmentation System - 0.5 meter accuracy when later phases deployed
Europe's Galileo (2013) - a few centimeter accuracy
The European Geostationary Navigation Overlay Service (EGNOS) is a satellite based augmentation system (SBAS) under development by the European Space Agency, the European Commission and EUROCONTROL. The official start of operations was announced by the European Commission on 1 October 2009. The system is showing outstanding performances in terms of accuracy (better than two metres) and availability (above 99%); it is intended to be certified for use in safety of life applications in 2010. The horizontal position accuracy is at the metre level.
The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including precision approaches to any airport within its coverage area. Actual performance measurements of the system at specific locations have shown it typically provides better than 1.0 metre (3 ft 3 in) laterally and 1.5 metres (4 ft 11 in) vertically throughout most of the contiguous United States and large parts of Canada and Alaska.
Multi-functional Satellite Augmentation System (MSAS) is a Japanese SBAS (Satellite Based Augmentation System). Typically GPS signal accuracy is improved from some 20 meters to approximately 1.5–2 meters in both the horizontal and vertical dimensions
Together with the American GPS, the Russian Glonass and other future newcomers, Europe's Galileo Satellites will provide more precise and reliable positioning and timing signals to citizens in Europe and around the globe. The 27 EU transportation ministers involved reached an agreement that it should be operational by 2013.
High precision will come from the technological characteristics of the system, as well as the number of satellites. From most locations, six to eight satellites will always be visible, allowing positions to be determined up to within a few centimetres.
GPS·C, short for GPS Correction, is a Differential GPS data source for most of Canada GPS·C improves real-time accuracy to about 1-2 meters.
Local Area Augmentation System allows users within 45 km of the LAAS ground station to perform GPS-based position fixes with 0.5-meter (95%) accuracy and to perform all civil flight operations up to non-precision approach.
Differential Global Positioning System (DGPS) is an enhancement to Global Positioning System that uses a network of fixed, ground-based reference stations to broadcast the difference between the positions indicated by the satellite systems and the known fixed positions.
The United States Federal Radionavigation Plan and the IALA Recommendation on the Performance and Monitoring of DGNSS Services in the Band 283.5–325 kHz cite the United States Department of Transportation's 1993 estimated error growth of 0.67 m per 100 km from the broadcast site but measurements of accuracy across the Atlantic, in Portugal suggest a degradation of just 0.22 m per 100 km
Nextbigfuture looked at Chip Scale Atomic Clocks and GPS Towers
The goal of the Chip-Scale Atomic Clock program is to create ultra-miniaturized, low-power, atomic time and frequency reference units that will achieve, relative to present approaches:
* 200X reduction in size (from 230 cm3 to <1 cm3),
* 300X reduction in power consumption (from 10 W to <30 mW), and
* Matching performance (1 X 10^-11 accuracy ⇒ 1 µ/day). Example of future payoff is wristwatch size high-security UHF communicator / jam-resistant GPS receiver
This scribd documents compiles some articles on using chip scale atomic clocks to augment global positioning systems. Atomic clocks in a GPS receiver would provide more accuracy especially more accurate altitude and longer term position tracking when out of satellite signal.
The DARPA plan for the atomic clock GPS receiver - Navigation nugget