Status of GPS/Loran Prototype for FAA Trials

by James H. Doty and Patrick Y. Hwang, Ph.D., Rockwell Collins, Inc., Linn Roth, Ph.D., Locus, Inc., and Mitchell J. Narins, Federal Aviation

Administration,

Portions of this work are being performed under subcontract SK-00-18 between Locus, Inc. and Advanced Management Technology, Inc. (AMTI) and under subcontract SK-02-02-001-00 between Rockwell Collins, Inc.

and AMTI under a Federal Aviation Administration (FAA) Broad Information Technology Services (BITS) contract.

Outline

• Interest in Loran

• GPS/Loran Integration Program

• Program Status

• Breadboard System design and test results

• Brassboard System features

• DOT’s Volpe Center study on GPS vulnerabilities spurred interest in independent, backup systems for both navigation and timing, i.e. critical infrastructure areas

• USCG interest in harbor entrance and approach• FAA interest for NPA (Non-Precision Approach)• Since 1997, Congress has provided $69M to further Loran

development, and estimate $21-25M in 2003• Loran infrastructure upgrade well underway, and overall

system performance will improve when upgrade complete

Resurgence In Loran Interest

GPS/Loran Integration Program

• The FAA is funding efforts to develop resources to evaluate and demonstrate the use of Loran to enhance the integrity and continuity of airborne navigation systems

• Rockwell Collins and Locus are under subcontracts to Advanced Management Technology, Inc. (AMTI)

– Locus is leading the effort to develop a prototype combined GPS & Loran H-field antenna and a standalone Loran receiver

– Rockwell Collins is leading the Integration of a Locus Loran receiver into a Collins Multimode Radio (MMR)

GPS/Loran Integration Program

Locus

Rockwell Collins

GPS/Loran Antenna

Brassboard GPS/Loran

Breadboard GPS/Loran

Loran Card

Standard SatMate 1020

Loran Receiver

StandardGNLU-930

MMR BreadboardGLIP

Loran CardICD GLIP Card

GPS/Loran Integration Effort

GPS/Loran Antenna Development

GPS Antenna Requirements

H-Field Loran Antenna

Loran Receiver

• Develop Eurocard size SatMate 1030

• Develop combined GPS/Loran H-field antenna

• Support Rockwell MMR integration

• Deliver prototype systems to FAA and Rockwell and support FAA tests

• Program efforts began January 2002

Locus :• Develop interface definition for

embedded Loran card • Perform integrity analysis and

develop integration algorithms• Integrate Locus Loran receiver

into Multimode Receiver (MMR)

• Support Locus antenna integration

• Deliver prototype system and support FAA tests

• Program efforts began May 2002

Rockwell Collins :

Program Responsibilities

Locus Program Status

Eurocard SatMate 1030 prototype receiver

functioning

Combined GPS/Loran prototype antenna

functioning

Uses certified ADF radome for flight tests

Locus Program Status

Front Panel

Rear Panel

Eurocard SatMate 1030 in stand-alone enclosure

Rockwell Collins Program Status

Breadboard GPS/Loran system completed and van tested

GLIP integration processor card for

Brassboard System assembled and tested

Current Rockwell Collins MMR

MMR - GNLU-930

Other GPS users(e.g. FMS, EGPWS)

L-bandL-band GPS PVTGPS PVT GLS PANGLS PAN

VHFVHF

UHFUHF

LocLoc

GlideslopeGlideslope

ILS ILS loc/glideloc/glide

Localizer/Glideslopedeviations

/GBAS/GBAS

C-band MLS az/el

• Current GNLU-930 MMR provides Localizer/Glideslope deviation information for approach, and PVT (position, velocity, time) information for area navigation and other uses

Brassboard MMR Architecture

• Locus SatMate 1030 Loran card will be embedded into Rockwell Collins MMR

• An independent GPS/Loran Integration Processor (GLIP) card will be added to minimize development risk

MMR - GNLU-930

L-bandL-band GLS PANGLS PAN

VHFVHF

UHFUHF

LocLoc

GlideslopeGlideslope

ILS ILS loc/glideloc/glide

Localizer/Glideslopedeviations

/GBAS/GBAS

GPS PVTGPS PVT

LF Loran Integration Proc.

Other GPS users(e.g. FMS, EGPWS)

New GPS Loran Integration Processor (GLIP) Functions

• To facilitate flight test evaluation of alternative Loran utilization techniques, multiple solutions of position and integrity limits are generated and output – “GPS-only” passes through GNSS solution– “Loran-only” recomputes position solution from Loran measurements – “Federated” GPS-Loran processes Loran and GPS measurements but

maintains independence between sensors for improved integrity– “Integrated” GPS-Loran calibrates Loran errors using GPS and produces a

more accurate position solution

GNSS I/O

Loran I/O

GPS-Only

Loran-Only

Federated GPS-Loran

Integrated GPS-Loran

Output I/O

ARINC I/O

Breadboard GPS/Loran System

J3

J2

J1

LoranAntenna

Cable 115VAC60 Hz

GPSAntenna +28VDC

CB2CB1

Data J4

DataJ5

GLIPProcessor

BoxLoran

RS-232

GNSS ARINC

GPS Loran

Nav OutputsGPSLoran

Serial Port #4

Loran PCControl

GNLU-930

WOW

ARINC

PowerSupply

Power Strip

Locus Satmate

Antenna

Serial Port A

J3

J2

J1

LoranAntenna

Cable 115VAC60 Hz

GPSAntenna +28VDC

CB2CB1

Data J4

DataJ5

GLIPProcessor

BoxLoran

RS-232

GNSS ARINC

GPS Loran

Nav OutputsGPSLoran

Serial Port #4

Loran PCControl

GNLU-930

WOW

ARINC

PowerSupply

Power Strip

Locus Satmate

Antenna

Serial Port A

GNSS

RS232 I/O

GLIP Functions

IntegratedSolutionARINC 429

Loran-OnlySolutionARINC 429

GPS-OnlySolutionARINC 429

Combined Data RS-232

ARINC I/O

Loran

Integrated GPS-Loran

Loran-Only

RS232 I/O

ARINC I/O

ARINC I/OGNSS

RS232 I/O

GLIP Functions

IntegratedSolutionARINC 429

Loran-OnlySolutionARINC 429

GPS-OnlySolutionARINC 429

Combined Data RS-232

ARINC I/O

Loran

Integrated GPS-Loran

Loran-Only

RS232 I/O

ARINC I/O

ARINC I/O

• Takes data from unmodified GNLU-930 MMR and SatMate 1020 Loran Receiver

• Recreates Loran Position solution from Loran timing measurements

• Produces an integrated GPS-aided Loran Solution

• Solutions available on both ARINC 429 and RS232 output formats

Breadboard Pallet I/O

110V AC 60 Hz

28V DC

Input powerOutput Data

ARINC 1 GPS onlyARINC 2 Loran onlyARINC 3 GPS/Loran

RS232 Combined data for collection

Loran H-field Antenna

GPS Antenna

GPS/Loran Breadboard

Antenna Connections

• The Breadboard GPS/Loran (GPS-aided Loran) solution is a Loran solution corrected with ASFs calibrated using GPS PVT data

• RS232 output includes ASF correction data, all three position solutions, and raw Loran Data messages

Breadboard Loran-Only Position Solution

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

No WeightingAmp WeightingPower WeightingLocus Reciever

-300 -280 -260 -240 -220 -200 -180 -160 -140 -120 -100-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0No WeightingAmp WeightingPower WeightingLocus Receiver

With only three stations weighting does not

change position solution

With more stations the weighting algorithm has a significant impact

on estimated position

Revised weighting algorithm overlays Locus

solution

• Extensive work was required to reproduce the Locus position solution from the delta-time measurements – Locus provided implementation details of the Locus weighting

algorithm– Position solution differences consistently well under 10 meters

Original Collins

Weighting

NoWeighting

Breadboard Van Testing

• The Breadboard GPS/Loran system was tested in the Collins Mobile Navigation Lab Van

• The antenna mount was raised to reduce interference from other van systems

Breadboard Position Outputs

42.027

42.028

42.029

42.03

42.031

42.032

42.033

42.034

42.035

42.036

-91.662 -91.66 -91.658 -91.656 -91.654 -91.652 -91.65 -91.648 -91.646

Longitude

Lat

itu

de

GPS-aided

Loran-only

GPS-only

Locus

100x100m

Breadboard Van Test Results

The GPS-aided Loran solution is corrected for position bias errors, but has noise characteristics matching the Loran-only solution

GPS

GPS-Aided Loran

Locus Loran Solution

GLIP Loran-only

100m

100m

Highway Breadboard Van TestingVan Test Results

42

42.05

42.1

42.15

42.2

42.25

42.3

-91.95 -91.9 -91.85 -91.8 -91.75 -91.7 -91.65

Longitude in degrees

Lat

itu

de

in d

egre

es

GPS-only

Loran-only

GPS-aided

Locus

1 km X 1 km

Van Test Results

42.2

42.21

42.22

-91.86 -91.85 -91.84 -91.83 -91.82 -91.81

Longitude in degreesL

atit

ud

e in

deg

rees

GPS-only

Loran-only

GPS-aided

Locus

1 km X 1 km

Passed under power lines

Start

End

Turn

GPS-aided Loran solution tracked GPS position well except for a brief anomaly when the van passed under high-voltage power lines

1 km

1 km

Average North Pos.

Offset

Average East Pos.

Offset

North Position Noise

East Position Noise

Locus receiver solution (no ASF corrections)

-164.3 -195.6 20.9 26.6

GLIP Loran-only solution(no ASF corrections)

-164.0 -196.4 20.9 26.8

GPS-Aided solution -2.0 -1.4 18.8 24.3

Typical Van Test Results

Van test solution errors relative to GPS in meters

GPS-derived ASF corrections dramatically reduce position error

in GPS-aided solution

ASF corrections do not significantly reduce noise

GPS-aiding Loran corrects slowly-varying ASF errors of Loran but a more tightly integrated solution is required to reduce noise

Brassboard System Features

• The brassboard system will integrate the Breadboard system functionality into the standard GNLU-930 MMR form factor

• Brassboard will include Locus SatMate 1030 prototype card and Collins GLIP card

• The integrated solution will be more tightly coupled to GPS to improve noise when GPS is available

• A new Federated GPS/Loran solution will be added for improved integrity monitoring

• All outputs will ARINC 429 and RS-232 monitor port will be eliminated

Brassboard MMR System

• Locus Loran card will be installed in place of the MLS slice on door of a modified GNLU-930

GLIP

Loran

MMR – Added Cards

• The new Collins GPS Loran Integration Processor (GLIP) card will be installed in the center card cluster in place of the FMS slice

• A ribbon cable from the GLIP to the Loran card will provide power and data communications

MMR Card Modifications

• The ILS and other MMR cards will remain unmodified (except for minor additions to the rear interconnect card)

ILS Card Power Supply

RearInterconnect

Card System Processor

Summary

• The FAA is supporting efforts to evaluate Loran for suitability of use in NPA and other airborne navigation applications

• Rockwell Collins and Locus are participating in coordinated programs to develop demonstration prototype GPS/Loran antenna and GPS/Loran MMR– Will be utilized by FAA to evaluate and demonstrate the use of

Loran to enhance integrity and continuity• The Breadboard GPS/Loran system has been completed and

van tested • The Breadboard system is working well and performance

characteristics are about as expected• Components for both the Brassboard System and GPS/Loran

Antenna have been assembled and are being tested