Admin Note: This is the planning behind the GPS and LORAN systems. IF you plan on using these systems…..you mind want to have a read.
Federal Radionavigation Planning
The Federal Government operates radionavigation systems as one of the necessary elements to enable safe transportation and encourage commerce within the United States. It is a goal of the Government to provide this service in a cost-effective manner. As the full civil potential of GPS and its augmentations is realized, the service provided by other Federally provided radionavigation systems is expected to decrease to match the reduction in demand for those services. However, operational or safety considerations may dictate the need for complementary navigation systems to support navigation or conduct certain operations. While some operations may be conducted safely using a single radionavigation system, it is Federal policy to provide redundant radionavigation service where required. A major goal for the US Government is to select a mix of common-use civil/military radionavigation systems that meets diverse user requirements.
Many factors are considered in determining the optimum mix of radionavigation systems. These factors include operational, technical, economic, institutional, and international parameters, and the needs of national defense. System accuracy, availability, integrity, continuity, and coverage are important indicators of system performance. Radio frequency spectrum issues are also considered. Certain unique parameters, such as antijamming performance, apply principally to military needs but also affect civil availability. Although radionavigation systems are operated primarily for safety of transportation and national defense, they also provide significant benefits to other civil, commercial, and scientific users. In recognition of this, the Federal Government considers the needs of these non-transportation users before making any changes to the operation of radionavigation systems.
The current US policy for the provision of Federally-operated radionavigation systems is contained in the 2001 FRP (Ref. 2).
Executive Summary
The Final Report of the President’s Commission on Critical Infrastructure Protection
concluded that Global Positioning System (GPS) services and applications are
susceptible to various types of interference, and that the effects of these vulnerabilities on
civilian transportation applications should be studied in detail. As a result of the report,
Presidential Decision Directive (PDD) 63 directed that the Department of Transportation
(DOT), in consultation with the Department of Defense (DoD), undertake a thorough
evaluation of the vulnerability of the national transportation infrastructure that relies on
the Global Positioning System.
The Volpe National Transportation Systems Center (RSPA/Volpe Center) conducted a
vulnerability analysis of GPS and identified the potential impact to aviation, maritime
transportation, railroads, and Intelligent Transportation Systems (ITS). The final report,
Vulnerability Assessment of the Transportation Infrastructure Relying on the Global
Positioning System
was published on August 29, 2001 (Ref.1). This study contained aseries of recommendations, which were reviewed and ultimately accepted by the
Department’s operating agencies. Recommendation sets were made relative to:
overarching issues related to GPS vulnerabilities, mitigating the vulnerabilities of the
GPS signal to disruption or loss, and mitigating the vulnerabilities of the transportation
systems resulting from the disruption or loss of the GPS signal.
Addressing this set of Volpe recommendations started with the key question, “What type
of backup systems must be in place to mitigate the disruption or loss of GPS?” The
answer led to the establishment of a Capabilities Assessment Task Force to develop a
recommended capabilities investment strategy for US radionavigation systems to meet
transportation infrastructure requirements for the next ten years. This recommendation
had to balance the plan to move toward a heavy reliance on satellite navigation with the
vulnerabilities of such an approach highlighted in the Volpe Study. According to the
study, “Backups for positioning and precision timing are necessary for all GPS
applications involving the potential for life-threatening situations or major economic or
environmental impact … The appropriate mix for a given application will result from
careful analysis of benefits, costs, and risk acceptance.”
To accomplish the analysis the Task Force focused on two tasks. The first task was to
conduct a multi-modal capabilities assessment of all radionavigation systems, both
current and planned, to satisfy the national need for radionavigation, positioning, and
timing. This included looking at the possibilities of using a system designed for one
operating agency as a backup for the needs of another. The output of this task was a
technical and cost perspective on the five most promising alternatives for system
architectures (or systems of systems). This output was the input for the second task,
which was to assess a set of alternative systems considering additional factors. These
factors included recommendations of the Volpe report on backups to GPS, potential
impact on other US Government agencies’ systems and operations, user equipage, and
interagency and international agreements. The final objective was a recommendation to
the Secretary on the most appropriate mix of radionavigation systems, from both a
capability and cost perspective, to satisfy the national need for radionavigation,
positioning and timing services for at least the next 10 years.
There are thousands of potential combinations of radionavigation systems. The Task
Force initially narrowed the field to eleven potential options by focusing on four crosscutting
radionavigation systems. These systems provide potential multi-modal
capabilities and have the greatest impact on the radionavigation system tradespace.
These systems are Loran and the GPS augmentations: Wide Area Augmentation System
(WAAS), Nationwide Differential GPS (NDGPS), and Local Area Augmentation System
(LAAS). The Task Force explored the ramifications of removing individual systems.
This included identifying what modal requirements could not be met and what systems
enhancements might be possible to meet those requirements. As a result, the Task Force
developed four alternative radionavigation mixes that could address the current user
needs for primary and backup systems. This includes two baseline options derived from
the 2001 Federal Radionavigation Plan (FRP) with and without Loran, and two
collocation options with and without Loran. However, not all four alternative mixes may
address potential future requirements. As requirements and applications continue to
evolve, each operating administration must ensure that adequate backups are available.
Cross-modal radionavigation systems must likewise be carefully coordinated. The
current collocation and synergy of NDGPS with the Continuously Operating Reference
Stations (CORS), Maritime Differential GPS Service (MDGPS), and the GPS Surface
Observing System (GSOS) has already avoided significant capital construction costs.
The potential for future collocation of WAAS, NDGPS, and Loran facilities should be
explored in conjunction with any future expansions of those systems.
The Task Force recommends the following:
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As investment decisions are made regarding individual radionavigation systems, theDepartment should review the overall radionavigation system program strategy to
ensure these systems meet the positioning, navigation, and timing requirements
across the entire transportation infrastructure in the most cost-effective and efficient
manner.
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The current role of the Department’s Investment Review Board (IRB) should bebroadened to serve this function for radionavigation system programs. This
would additionally require expanding the membership of the IRB to include the
Under Secretary of Transportation for Policy as a voting member.
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GPS modernization, to include the implementation of the second and third civilsignals, should proceed as expeditiously as feasible in order to meet a multitude of
civil applications and safety-of-life missions that are critical to our transportation
infrastructure.
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Every effort should be made to meet, and accelerate if possible, the operationalimplementation schedule for these new GPS capabilities.
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Complete the evaluation of enhanced Loran to validate the expectation that it willprovide the performance to support aviation Non precision Approach (NPA) and
maritime Harbor Entrance and Approach (HEA) operations.
•
If enhanced Loran meets the aviation NPA and maritime HEA performancecriteria, and is cost effective across multiple modes, the Federal Government
should operate Loran as an element of the long-term US radionavigation system
mix.
•
If enhanced Loran does not meet expected performance criteria, or is not costeffective across multiple modes, the Federal Government should operate the
system only to the end of 2008 to allow users sufficient time to transition to
alternate navigation aids.
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Complete three additional radionavigation system studies, in addition to the enhancedLoran evaluation, as follows:
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The USCG will, in cooperation with the FAA, assess the ability of the Wide AreaAugmentation System (WAAS) to meet marine requirements.
•
The FHWA will, in cooperation with the FRA and the USCG, assess the ability ofthe High Accuracy Nationwide Differential Global Positioning System (HANDGPS)
to meet surface (i.e., highway, rail, and marine) requirements.
•
The FAA will assess the ability of the Local Area Augmentation System (LAAS)to meet precision approach requirements for aviation.
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The collocation of WAAS, NDGPS, and Loran facilities should be explored inconjunction with any future expansions of those systems, contingent on the results of
the enhanced Loran evaluation and benefit-cost analysis.
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The Department should explore funding strategies to ensure that NDGPS isimplemented in accordance with the schedule presented in the 2001 FRP.
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As requirements and applications continue to evolve, the potential for variousradionavigation systems to contribute to the overall radionavigation mix should be
periodically evaluated.
This document is composed of the following sections:
Section 1 – Introduction: Describes the background, purpose, and scope of the
Radionavigation Systems Task Force. It summarizes events leading to the preparation of
this document and tasks that were conducted under this study.
Section 2 – Current Situation: Describes Federal radionavigation planning. It also
summarizes current radionavigation systems as well as future potential radionavigation
systems under research & development.
Section 3 – Modal Requirements & System Capabilities Assessment: Describes the
technical approach used by the Task Force. It lays out the system requirements for
transportation and non-transportation users and compares them to the capabilities of each
radionavigation system.
Section 4 – Selection Methodology: Describes the process of establishing a number of
alternative radionavigation system mixes and how they were evaluated and down
selected to 3 alternatives mixes and a baseline.
Section 5 – Backups to GPS: Describes current and future modal backups to
radionavigation systems.
Section 6 – Radionavigation Systems Mix Analysis: Describes the final alternative
mixes recommended by the Task Force. This includes a baseline and 3 alternative
mixes.
Section 7 – Loran Decision: Describes the various options available regarding the
Loran-C decision and recommendation from the Task Force.
Section 8 – Cost: Discusses the program funding for the various radionavigation
systems.
Section 9 – Conclusions and Recommendations: Presents the Task Force final
conclusions and recommendations.
Appendices
References
Study Team