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The on-board maritime PNT Module – Concept & Status of Realization as a Demonstrator

Ralf Ziebold, Z. Dai, Th. Noack, E. EnglerGerman Aero Space CentreInstitute of Communications and NavigationNautical Systems Group


Table of content

Introduction / PNT Module concept Introduction / PNT Module concept

PNT Unit demonstrator developmentPNT Unit demonstrator development


PNT relevant user needs within E-Navigation

PNT information

Improved reliability

Indication of reliability

Alert management

“Before mariners can feel confidentabout relying on systems underthe e-navigation concept, theymust prove far more reliable thanmany of the present systems”

IMO, NAV 55/WP.5


Current status: Integrated Navigational System (INS)

Shipboard Sensor Layer

Shipboard Processing Layer

GNSS Receiver

DGNSS Receiver

Multi Radio Navigation Receiver

etc.

WWRNSsensors

Gyro / Compass

Speed / Log

Othershipboardsensors

etc.

ROTI

interface, point of type approval

PVT

PVT

PVT

N

N

N

Check Matrix of PNT data

realized byINS

PNT

Integrity(plausibility,

consistency)

Alerts

INS is not a mandatory system, but if it is installed it can replace single sensor requirements


Integrity definitions

- IMO Integrity Definition: (IMO Resolution A.915(22) Requirements for a future GNSS)

The ability to provide users with warnings within a specified time when the system should not be used for navigation

Integrity: timely (TTA) warning, based on accuracy estimation Protection level (PL): bounds true error under consideration of remaining integrity risk Available: PL < Alert limit (AL)

Continuity of integrity and accuracy

Availability: probability that the positioning service and the integrity monitoring service are available and provide the required accuracy, integrity and continuity performance

General structure of GNSS service specification

Accuracy: The degree of conformance between the estimated or measured parameter of a craft at a given time and its true parameter at that time. (95% confidence)


From service to user level integrity

Current user level integrity definition

- IEC INS standard (61924:2006)

property of information as being accurate and valid with regard to specified requirements and verified by comparing data from more than one independent source

large gap between service level integrity and user level integrity

1st. Approach: Establish user level integrity comparable to GNSS service specification (based on accuracy estimation) onboard the vessel

=> Over bound all possible errors (threads)


PNT Unit Approach

Shipboard Sensor Layer

Shipboard Processing Layer

GNSS Receiver

DGNSS Receiver

Multi Radio Navigation Receiver

etc.

WWRNSsensors

Gyro / Compass

Speed / Log

Othershipboardsensors

etc.

ROTI

interface, point of type approval

PVT

PVT

PVT

N

N

N

PNT (data processing)

Unit

as part of INS

best PNT

Integrity

(accuracy)

Alerts

Other PNT relevant Input Data (Radar, MSI, AIS,…)

raw

raw

raw

raw

raw

raw


PNT Unit

Processing Channel 1




Processing Channel N

Ve

rsio

n d

ep

en

de

nt

Ch

ec

k M

ati

x

PNT Unit Approach


Kalman filter estimates (bias check)

Kalman filter estimates (bias check)

Integrity monitoring

Individual sensor data checkPlausibility check (e.g. speed ≤ max. ship speed)

Individual sensor data checkPlausibility check (e.g. speed ≤ max. ship speed)

Three step process of integrity monitoringThree step process of integrity monitoring

11Consistency check

comparison of outputs generated by differentsensors x ≤ Threshold

Consistency check

comparison of outputs generated by differentsensors x ≤ Threshold

22Fault detection and identification in the integration algorithmUsing capabilities ofsensor fusion methodse.g. Kalman Filter

Fault detection and identification in the integration algorithmUsing capabilities ofsensor fusion methodse.g. Kalman Filter

33

Innovation-based approaches

Innovation-based approaches

Residual-based approaches

Residual-based approaches

Parallel solution of multiple sub-filters

Parallel solution of multiple sub-filters


Table of content

Introduction / PNT Module concept Introduction / PNT Module concept

Status of demonstrator developmentStatus of demonstrator development

Single Sensor characterization Single Sensor characterization

Results tightly coupled GNSS -IMU Integration Results tightly coupled GNSS -IMU Integration


Measurement campaigns: July /August 2011

- Survey and research vessel DENEB (BSH)

First experimental results

(2)

(3)

(1)

- Standard sensors- IALA Beacon DGPS- Doppler Log- EM Log - Gyro compass

- Additional sensors- IMU- 3x GNSS receiver

(dual frequency RTK)


Characterization of sensors quasistatic scenario: GPS Compass – IMU leveling

-180

-179.8

-179.6

-179.4

-179.2

-179-179

roll

[°]

-0.4

-0.2

0

0.2

0.4

pitc

h [

°]

0 2000 4000 6000 8000 10000100

100.2

100.4

100.6

100.8

101

time t [s]

yaw

[°]

Pitch angle

Roll angle

Yaw angle

GPS compassIMU leveling

-179.6 -179.35 -179.1

roll angle

roll angle [°]

occ

ura

nce

mean= -179.37° std= 0.06°

-0.1 0.15 0.4

pitch angle

pitch angle [°]

occ

ura

nce

mean= 0.19° std= 0.008°

100.3 100.55 100.8

yaw angle

yaw angle [°]

occ

ura

nce

mean= 100.54° std= 0.02°

-179,5 -179,4 -179,3 -179,2

IMU roll angle

roll angle [°]

occ

ura

nce

mean= -179.36° std= 0.04°

0 0.1 0.2 0.3

IMU pitch angle

pitch angle [°]

occ

ura

nce

mean= 0.19° std= 0.005°

GPS compass IMU leveling

1500 2000 2500 3000 3500-0.02

-0.01

0

0.01

0.02

Variation of distance between GPS antennas

time t [s]

delta

dis

tanc

e [m

]

12

3


Characterization of Sensors for heading determination: GPS Compass – Gyro Compass

Calm sea (7/5/2011 8-9 a.m. UTC)

500 1000 1500 2000 2500 3000-1

0

1

2

3Ships roll and pitch angle determined by GPS Compass

2011 7 5 8h

time t [s]

angl

e [°

]

500 1000 1500 2000 2500 3000-200

0

200

400

600Heading determined by Gyrocompass and GPS Compass

time t [s]

head

ing

angl

e [°

]

500 1000 1500 2000 2500 3000-2

-1

0

Delta Heading Gyro vs. GPS Compass

time t [s]

delta

ang

le [

°]

roll

pitch

Gyro Compass

GPS Compass • larger gyro compass error after turning maneuver

0 500 1000 1500 2000 2500 3000

-0.1

-0.05

0

0.05

0.1

0.15Variation of distance between GPS antennas

time t [s]

de

lta d

ista

nce

[m]

1-2

1-3

2-3


-50 0 50 100 150 2000

500

1000

1500

2000

2500

3000

3500

4000

East [m]

No

rth

[m]

Trajectory with respect to the starting point

GPS onlyGPS/IMU Integration

10: 9 10:17 10:25 10:34 10:42 10:50 10:590

5

10

15

20

25

30

Local time [hour:minute]

Ab

solu

te e

rro

r [m

]

Horizontal error with respect to the reference trajectory

GPS onlyGPS/IMU Integration

Tightly-coupled GPS/IMU integration with satellite filteringTightly-coupled GPS/IMU integration with satellite filtering

Accuracy improvementAccuracy improvement

Tightly coupled GPS/IMU


Innovation of satellites

EastWest

North

South

3

5

6

7

8

10

13

15

19

21

26

28

Spurious MeasurementsSpurious Measurements

10:1 10:30 10:59-10

0

10PRN: 3

10:1 10:30 10:59-10

0

10PRN: 5

10:1 10:30 10:59-10

0

10PRN: 7

10:1 10:30 10:59-10

0

10PRN: 8

10:1 10:30 10:59-10

0

10PRN: 10

10:1 10:30 10:59-10

0

10PRN: 13

10:1 10:30 10:59-10

0

10PRN: 15

10:1 10:30 10:59-10

0

10PRN: 19

10:1 10:30 10:59-10

0

10PRN: 21

10:1 10:30 10:59-10

0

10PRN: 26

Innovation Code X-axis: GPS epochs Y-axis: Innovation in meters

10:1 10:30 10:59-10

0

10PRN: 28

Satellites with low elevation anglesSatellites with low elevation angles

Low weightLow weight CancellationCancellation


PNT Unit interfaceOpen question:

Input interface

- accuracy, integrity, continuity, availability depended on- operational region- maneuver status: automatic docking , ???

How this information is transferred to PNT Module?- operational region: ENC layer ?- maneuver status ??

Output interface:

- What integrity information should be delivered how?- Visualization of integrity information


Next steps

- Finalize implementation of PNT Unit demonstrator v 1.0

- Implementation of new sensors- Refinement of integrity monitoring schemes- New sensor fusion schemes


Thank You For Your Attention

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