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Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 61
Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 62
Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 63
Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 64
Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 65
Suggested Citation:"SUMMARY." National Research Council. 1995. The Global Positioning System: A Shared National Asset. Washington, DC: The National Academies Press. doi: 10.17226/4920.
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Page 66

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GPS APPLICATIONS AND REQUIREMENTS 61 Findings The presence of SA has little or no effect on the ability to use GPS for orbit determination, but A-S limits the performance of orbit determination for spacecraft that rely on dual-frequency measurements, such as Topex/Poseidon. SA has no effect on the accuracy of GPS attitude determination methods for spacecraft. A-S may place some limitations on achievable accuracy, but so do design parameters related to receiver electronics and antenna structure. The ability to use GPS for orbit determination on board geosynchronous satellites will be lost if the Block IIR and IIF spacecraft are built with narrower beamwidth antennas than the Block II/IIA satellites. SUMMARY Although this chapter does not represent a complete list of all GPS applications and their requirements, it should be clear from its content that the Global Positioning System has become an integral part of our nation's technical infrastructure, which contributes to our security, economy, and overall quality of life. Indeed, a fully exhaustive list of GPS applications may be impossible to compile, for as soon as it was completed, dozens of new and innovative applications, such as navigation systems for the visually impaired, would be developed that exploit GPS to the limits of its technological capability. Although requirements for currently undiscovered applications such as this one cannot be quantified, a strong case can be made for not only maintaining the basic system's operational capability but also for continuously improving it in order to meet the increasingly demanding requirements of a multitude of military and civilian users who rely on GPS on a routine basis. The tables included in this summary represent a compilation of the GPS applications that have been discussed in this chapter. Military applications with accuracy requirements currently unmet by the PPS are included in Table 2-11, and civil applications are grouped according to their accuracy requirements in tables 2-12 though 2-16. As these tables and the preceding discussions in this chapter clearly illustrate, the civilian applications that currently require augmentation or enhancement of the GPS SPS far outweigh those that do not. Most integrity and availability requirements for civilian applications are also unmet by the GPS SPS and are highlighted in the tables through the use of grey shading. Candidate technical improvements and modifications to the basic GPS that would enhance its functionality and make it more capable of meeting the requirements of both civilian and military users are discussed in the next two chapters.

GPS APPLICATIONS AND REQUIREMENTS 62 Table 2-11 Summary of Military Applications with Accuracy Requirements Unmet by the GPS PPS as Currently Specifieda Application Accuracy Integrity 1 minus PHE times Time to Alarm PMD Aviation Non-precision Sea Approach/ 12.0 m (2 drms) 0.999 10s Landings Precision Approach/Landings 125 m (2 drms) 0.999 6s Unprepared Surface Precision Sea Approach/ 0.6 m (2 drms) 0.999 6 Landings Mine Warfare Anti-mine Countermeasures < 5.0 m CEP Not specified Not specified Special Warfare Combat Swimming 1.0 m CEP Not specified Not specified Land Warfare & Insertion/ 1.0 m CEP Not specified Not specified Extraction Amphibious Warfare Artillery & Reconnaissance < 6.0 m CEP Not specified Not specified Precision-guided Munitions 3.0 m CEP Not specified Not specified a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter. Table 2-12 Summary of Civilian Applications with Accuracy Requirements of 100 Meters or Greater (currently achievable with the basic GPS SPS)a Application Accuracy (2 drms) Integrity Availability 1 minus PHE times Time to Alarm PMD Aviation En route Oceanic 23 km Not specified 30 s 99.977% En route through Non- 100 m 1-1x10-7 per hour 8s 99.999% precision Approach/ Landings Domestic Automatic 200 m Not specified Not specified 99.999% Dependent Surveillance (ADS) Maritime Oceanic Navigation 1800 to 3700 m Not specified Not specified 99.0% Coastal Navigation 460 m Not specified Not specified 99.7% a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter.

GPS APPLICATIONS AND REQUIREMENTS 63 Table 2-13 Summary of Civilian Accuracy Requirements Between 25 and 100 Metersa Application Accuracy (2 Integrity Availability drms) 1 minus PHE Time to Alarm times PMD ITS and Vehicle Fleet Management 25 to 1500 m Not specified 1 to 15 s 99.7% Navigation/ (AVL/AVI) Position Location Emergency Response 75 to 100 m Not specified 1 to 15 s 99.7% Vehicle Command 30 to 50 m Not specified 1 to 15 s 99.7% and Control Accident Data 30 m Not specified 1 to 15 s 99.7% Collection Spacecraft Orbit Determination 50 m Not specified Not specified Not specified (Satellites) (real time) a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter. Table 2-14 Summary of Civilian Accuracy Requirements Between 10 and 25 Metersa Application Accuracy Integrity Availability (2 drms) 1 minus PHE Time to Alarm times PMD Aviation TCAS 14.4 m Not specified Not specified Several Days Surface Surveillance 24.0 m Not specified Not specified 99.87% Maritime Recreational Boating 10.0 m Not specified Not specified 99.9% Vessel Traffic Services 10.0 m Not specified Not specified 99.9% ITS Infrastructure 10.0 m Not specified 1 to 15 s 99.7% Management Search & rescue Location Determination 10.0 m Not specified minutes 99.0% Oceanography Real-time Navigation 10.0 to 30.0 m Not specified Not Not specified and Positioning a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter.

GPS APPLICATIONS AND REQUIREMENTS 64 Table 2-15 Summary of Civilian Accuracy Requirements Between 1 and 10 Metersa Application Accuracy (2 Integrity Availability drms) 1 minus PHE Time to Alarm times PMD Aviation CAT I Approach/ 7.6 m 1-4 x 10-8 per 5.2s 99.9% Landing approach CAT II Approach/ 1.7 m (vertical) 1 -0.5 x 10-9 per 2.0s Not specified Landing approach Maritime Harbor/Harbor 8.0 to 20.0 m Not specified 6 to 10 s 99.7% Approach Navigation Inland Waterway 3.0 m Not specified 6 to 10 s Not specified Navigation Railroad Train Control 1.0 m Not specified 5s 99.7% ITS and Vehicle Highway 5.0 to 20.0 m Not specified 1 to 15 s 99.7% Navigation/ Navigation and Position-Location Guidance Mayday/Incident 5.0 to 30.0 m Not specified 1 to 15 s 99.7% Alert Automated Bus/ 5.0 to 30.0 m Not specified 1 to 15 s 99.7% Rail-Stop Annunciation Collision 1.0 m Not specified 1 to 15 s 99.7% Avoidance, Control Collision 5.0 m Not specified 1 to 15 s 99.7% Avoidance, Hazardous Situation Hazmat Vehicle or Cargo 5.0 m Not specified 1s 99.7% Transport Location Land Off-road Vehicles, 5.0 m Not specified Minutes 99.0% Recreation Hikers, Back-country Skiers, etc. Earth Science Airborne 3.0 m (vertical) Not specified Minutes Not specified Geophysics Mapping/ Geographic 1.0 to 10.0 m Moderate Not specified 98% Surveying Information Systems (GIS) a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter.

GPS APPLICATIONS AND REQUIREMENTS 65 Table 2—16 Summary of Submeter Civilian Accuracy Requirementsa Application Accuracy (2 Integrity Availability drms) 1 minus PHE Time to Alarm times PMD Aviation CAT III Approach/ 0.6 to 1.2 m 1 -0.5 X 10-9 2.0 s Not specified Landing (vertical) per approach Precision Automatic Vehicle 0.05 m Not specified 5.0 s 99.7% Farming Guidance Mapping/ Photogrammetry 0.02 to 0.05 m Not specified Minutes 98.0% Surveying/ Geodesy Remote Sensing 0.1 to 20.0 m Not specified Not specified 98.0% Geodesy 0.01 to 0.05 m Not specified Hours 98.0% Mapping 0.1 to 10.0 m Not specified Hours 98.0% Surveying 0.01 to 10.0 m Not specified Hours 98.0% Earth Science Oceanography (ocean 0.01 m Not specified Hours Not specified circulation determination) Geodynamics 0.001 m + 109 x Not specified Hours Not specified baseline length Spacecraft Orbit Determination ± 0.001 m Not specified Not specified Not specified (satellites) (post-process) Attitude Determination 3 x 10-6 degrees Not specified Not specified Not specified (0.01 arc second), 2σ a.References and/or additional notes for each of the requirements listed in this table can be found by referring to previous tables (2-1 through 2-10) included in this chapter.

GPS APPLICATIONS AND REQUIREMENTS 66

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The Global Positioning System (GPS) is a satellite-based navigation system that was originally designed for the U.S. military. However, the number of civilian GPS users now exceeds the military users, and many commercial markets have emerged. This book identifies technical improvements that would enhance military, civilian, and commercial use of the GPS. Several technical improvements are recommended that could be made to enhance the overall system performance.

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