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The Loran Integrity Performance Panel (LORIPP). The LORIPP Team Loran Team Meeting McLean, VA July 30, 2002. LORIPP Background. What is LORIPP and why does it exist? Determine Requirements (System Engineering) Identify Threats to Loran and Determine Threat Allocations (Fault Tree)

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the loran integrity performance panel loripp

The Loran Integrity Performance Panel (LORIPP)


Loran Team Meeting

McLean, VA July 30, 2002

loripp background
LORIPP Background
  • What is LORIPP and why does it exist?
    • Determine Requirements (System Engineering)
    • Identify Threats to Loran and Determine Threat Allocations (Fault Tree)
    • Bound/Mitigate Effects of these Threats
    • Develop Threat Models
    • Provide Substantiated Information on Loran Capabilities
  • What will we accomplish?
    • Prove Stand Alone Loran Can Act as a Redundant Navigation System (RNP 0.3 or 0.5)
threats to loran integrity
Threats to Loran Integrity
  • Transmitter
  • Propagation Effects
    • Interference (Atmospheric Noise, P Static, Sky Wave)
    • Ground Wave Propagation Phenomena (ASF, ECD, SNR)
  • Receiver
loripp work plan
LORIPP Work Plan
  • Transmitter Performance (LSU, PIG, Tom G., NAVCEN)
  • Receiver Algorithms & Performance (PIG, Stanford, USCGA)
  • Fault Tree (Stanford, Kevin B., NAVCEN)
  • System Engineering (PIG, Bob W.)
  • P-Static Evaluation (Bob E., Bob T., Bob L., Bob W., Frank G., Kevin B.)
  • Atmospheric Noise (Stanford, PIG, Kevin B., Bob W.)
  • Ground Wave Propagation: ASF, ECD and Signal Strength (Bob W., USCGA, NAVCEN, LSU, PIG, Tom G., OU, FAATC)
  • Loran Communications (Stanford, PIG, Frank G.)
  • Sky Wave (Bob W., USCGA)
  • Documentation & Meeting Logistics (Tom G., Stanford, NAVCEN)
system engineering
System Engineering
  • Development of Coverage Analysis Tools
  • Calculation of Continuity & 95% Accuracy
  • Reliability, i.e., Mean Time between Failures, etc.
    • Avionics
    • New Transmitter Equipment (validate assumptions)
fault tree
Fault Tree
  • Integrity Fault Tree
  • Continuity Fault Tree
  • Determine Allocations in Error Budget
    • ECD (propagation, receiver calibration, receiver noise)
    • TOA (receiver noise)
    • Tails of the distributions
preliminary integrity fault tree
Preliminary Integrity Fault Tree

Probability (HPE > HPL)

> 10-7/hour



Caused HMI



Caused HMI



Caused HMI














transmitter performance
Transmitter Performance
  • Determine ABS Threshold, Time to Blink from Onset of Fault, Probability of Out of Tolerance w/o blink
  • Determine Transmitted ECD Tolerance, Blink on transmitted ECD? ***
  • Determine Threat Monitor Requirements at transmitter, Certification Requirements for Monitors
  • Calibration re UTC
  • Chain Operations
    • TOE verus SAM
      • Analysis of coverage under each situation
    • Control of TOE to UTC vs measurement of TOE to UTC and transmission of measured offset
receiver algorithms performance 1 2
Receiver Algorithms & Performance (1/2)
  • Determine the probability of false alarm & missed detection of blink/off air at given SNR (given time to alarm requirement)
  • Establish SNR Threshold (for reliably identifying the correct station & cycle) with 7 9s of confidence
  • Master independent, multi-chain navigation
    • Resolution of 200 usec cross chain lane ambiguities
    • Identification of secondary w/o master
  • Loran Cycle Integrity Calculations
    • Weighted Sum Squared Error vs Sum Squared Error
    • Analysis of probability of cycle slips after verifying cycle integrity
receiver algorithms performance 2 2
Receiver Algorithms & Performance (2/2)
  • Input from Potential Manufacturers – Validate Assumptions of HMI Analysis
  • Determine ECD Requirement
  • Determine Loop Time Constants
  • Develop Simulator
    • Averaging time
    • HPL calculation
basic receiver hmi algorithm

Cycle Resolution

Verifies that the correct cycle is being tracked

Determine Pwc (probability of being on the wrong cycle)

HPL Calculation

Determines the 99.99999% confidence bound on horizontal error

Determine HPL

HPL < 0.3 NM

HPL < 0.5 NM

Pwc < 1x10-7

Cannot meet RNP 0.3 or 0.5 Requirements

HPL > 0.3 NM (RNP 0.3)

HPL > 0.5 NM (RNP 0.5)

Pwc > 1x10-7

Basic Receiver HMI Algorithm
p static
P Static
  • Educate LORIPP via tutorial paper and briefing.
  • Determine how P static fits into Fault Tree
    • Different faults caused by P static and Allocations
  • What would the continuity allocation be?
  • What is max level of P static
  • Developing H-field Antenna Test Plan and, at a minimum, determine a figure for SNR drop outdoors
atmospheric noise
Atmospheric Noise
  • Determine the necessary analysis level, i.e., 95%, 99%, or 99.9%, worst time period or averaged over time?
  • Determine and Develop Applicable Databases
  • Time Domain Model for Simulation
  • Determine the credit that can be claimed for non-linear processing
  • Implement Results in Simulator and Receiver
ground wave propagation asf ecd and signal strength
Ground Wave Propagation: ASF, ECD and Signal Strength
  • Data Collection
    • Guidance/requirements definition for data collection effort (also collecting ECD & SNR data)
    • Coordinate with Atmospheric Noise Threat Model
  • Data Analysis
    • 99.99999% bounds on remaining errors
    • Correlated vs. Uncorrelated terms
    • Mathematical modeling & prediction including terrain of SS, ECD, & ASF?
sky wave
Sky Wave
  • Quantify effects on TOA bias
  • Quantify effects on ECD bias
  • Receiver technology for mitigation
  • Integrity Allocation & Threat Model
loran communications
Loran Communications
  • Effects on Navigation if Signals are Modulated
  • Impact on Availability, Integrity, Accuracy, & Continuity if Loran Data is Transmitted
    • What data?
    • And at what rates?
  • Quantify the benefits provided by the data channel in improving Loran Nav. performance (Availability, Integrity, Accuracy, & Continuity)
documentation meeting logistics
Documentation & Meeting Logistics
  • Collect White Papers from Briefings
  • Loran/LORIPP Web resource?
  • Meeting Minutes
  • Organize Project and Arrange Priorities
  • Determine Documentation Methodology
  • The LORIPP just had its first meeting this past week
    • The major (critical) issues for Loran RNP 0.3 were discussed
    • A work plan was developed to gather the data and perform the analysis necessary to prove Loran performance
    • Future meetings are planned to further develop the integrity analysis – late September