Airport ASF Mapping Methodology Update

Abstract

In 2001, the Volpe National Transportation Systems Center completed an evaluation of GPS vulnerabilities and the potential impacts. 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. 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 non-precision 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). A Working Group is currently developing the procedures to be used to map the ASF values for an airport. The draft procedure has been tested. This paper discusses the results of this data collection: how well the spatial variation seen on the ground matches the BALOR model prediction and the implications of this on the proposed procedure, an analysis of how many ASFs should be required to meet RNP 0.3 for each airport based on geometry and ASF variation in the area, and results of the position accuracy obtained by the aircraft flying approaches when using the airport ASF values.

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Document Details

Document Type
Technical Report
Publication Date
Oct 01, 2005
Accession Number
ADA575170

Entities

People

  • Gregory Johnson
  • Kevin Bridges
  • Mark Wiggins
  • Michael Kühn
  • Peter F. Swaszek
  • Richard Hartnett

Organizations

  • United States Coast Guard Academy

Tags

Communities of Interest

  • Air Platforms
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Accuracy
  • Aircrafts
  • Backup Systems
  • Coast Guard
  • Digital Signal Processing
  • Electrical Engineering
  • Engineering
  • Failure Mode And Effect Analysis
  • Field Tests
  • Grids
  • Loran
  • Measurement
  • Navigation
  • Radio Navigation
  • Rhode Island
  • Signal Processing
  • Simulations

Readers

  • Aviation Safety and Air Traffic Management
  • Munitions and Ordnance Engineering
  • Wave Propagation and Nonlinear Chaotic Dynamics.

Technology Areas

  • Space