Loran ASF Variations as a Function of Altitude

Abstract

In 2001, the Volpe National Transportation Systems Center completed an evaluation of GPS vulnerabilities and the potential impacts to transportation systems in the United States. One of the recommendations of this study was for the operation of backup system(s) to GPS; Loran-C was identified as one possible backup system. The Federal Aviation Administration (FAA) has been leading a team consisting of members from industry, government, and academia to evaluate the future of Loran-C in the United States. In a recently completed Navigation Transition Study, the FAA concluded that Loran-C, as an independent radio navigation system, is theoretically the best backup for the Global Positioning System (GPS). However, in order for Loran-C to be considered a viable back-up system to GPS, it must be able to meet the requirements for nonprecision approaches (NPA's) for the aviation community, and the Harbor Entrance and Approach (HEA) requirements for the maritime community. A significant factor limiting the accuracy of a Loran system is the spatial and temporal variation in the times of arrival (TOAs) observed by the receiver. A significant portion of these variations is due to the signals propagating over paths of varying conductivity; these TOA corrections which compensate for propagating over non-seawater paths are called additional secondary factors (ASFs). Hence, a key component in evaluating the utility of Loran as a GPS backup is a better understanding of ASFs and a key goal is deciding how to mitigate the effects of ASFs to achieve more accurate Loran-C positions while ensuring that the possibility of providing hazardous and misleading information (HMI) will be no greater than 1x10(-7).

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Document Details

Document Type
Technical Report
Publication Date
Oct 01, 2005
Accession Number
ADA575169

Entities

People

  • Christian Oates
  • Gregory Johnson
  • Kevin Bridges
  • Peter F. Swaszek
  • Richard Hartnett
  • Ruslan Shalaev

Organizations

  • United States Coast Guard Academy

Tags

Communities of Interest

  • Air Platforms

DTIC Thesaurus Topics

  • Accuracy
  • Altitude
  • Backup Systems
  • Coast Guard
  • Electrical Engineering
  • Engineering
  • Failure Mode And Effect Analysis
  • Global Positioning Systems
  • Line Of Sight
  • Loran
  • National Transportation System
  • Navigation
  • New England
  • Radio Navigation
  • Rhode Island
  • Transportation Infrastructure
  • United States

Readers

  • Aviation Safety and Air Traffic Management
  • Inertial Navigation Systems.
  • Strategic Security Studies

Technology Areas

  • Space