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www.DLR.de • Chart 1 >Resilient PNT: From PNT Unit concept to first realization> R. Ziebold > e-Navigation Underway 01/30/2013

Resilient PNT:

From PNT-Unit concept to first realization

Ralf Ziebold, Z. Dai, L, Lanca, D. Minkwitz, T. Noack, E. Engler

German Aerospace Centre

Institute of Communications and Navigation

Nautical Systems Group


PNT relevant user needs within E-Navigation

PNT information

Improved

reliability

Indication of

reliability Alert

management

IMO, NAV 55/WP.5

PNT System Generic Architecture

INS

ship-side components

Augmentation Services

- 1 … N

PNT relevant MSP

etc.

PNT relevant MSI

Backup Services

- 1 … K

World Wide Radio Navigation Systems (WWRNS)

shore-side services links

functional

links

physical

links PNT Module PNT Module

MGBAS Service (Research Port Rostock)


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

Availability

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

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

=> Over bound all possible errors (threads)

large gap between service level integrity and user level integrity


PNT Unit Approach

Shipboard

Sensor Layer

Shipboard

Processing Layer

GNSS Receiver

DGNSS Receiver

Multi Radio Navigation

Receiver

etc.

WWRNS

sensors

Gyro / Compass

Speed / Log

Other

shipboard

sensors

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


Measurement campaigns

- Survey and research vessel DENEB (BSH)

First experimental results

(2)

(3)

(1)

Additional sensors

- Tactical grade IMU

- 3x GNSS receiver

(dual frequency RTK)


-50 0 50 100 150 200

0

500

1000

1500

2000

2500

3000

3500

4000

East [m]

No

rth

[m

]

Trajectory with respect to the starting point

GPS only

GPS/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

so

lute

err

or

[m]

Horizontal error with respect to the reference trajectory

GPS only

GPS/IMU Integration

Tightly-coupled GPS/IMU

integration with satellite filtering Accuracy improvement

Tightly coupled GPS/IMU


Innovation of satellites

E a s tW e s t

N o rth

S o u th

3

5

6

7

8

1 0

1 3

1 5

1 9

2 1

2 6

2 8

Spurious 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 angles

Cancellation


-250 -200 -150 -100 -50 0 50 100-100

-50

0

50

100

150

200

East [m]

Nort

h [m

]

Trajectory with respect to the starting point

GPS only

GPS/IMU (sat. filter)

GPS/IMU (no sat. filter)

Dynamic model (herein IMU) can

smooth the positioning results

Integration with/without satellite filtering

Integrity monitoring on each

measurement has dominant effects

in the accuracy improvement

IMU contingency functionality


50 100 150 200 2500

2

4

6

8

10

Pos E

rr [

m]

Epoch [s]

50 100 150 200 2500

0.2

0.4

0.6

0.8

1

Vel E

rr [

m/s

]

-6 -4 -2 0 2 4 60

200

400

600

East [m]

Notr

h [

m]

GPS/IMU

RTK

IMU only

50 100 150 200 2500

2

4

6

8

10

Pos E

rr [

m]

Epoch [s]

50 100 150 200 2500

0.2

0.4

0.6

0.8

1

Vel E

rr [

m/s

]

-50 -40 -30 -20 -10 0 100

200

400

600

East [m]

Notr

h [

m]

GPS/IMU

RTK

IMU only

50 100 150 200 2500

2

4

6

8

10

Pos E

rr [

m]

Epoch [s]

50 100 150 200 2500

0.2

0.4

0.6

0.8

1

Vel E

rr [

m/s

]

120 140 160 180 200 220 240 260 280 300150

200

250

300

350

East [m]

Notr

h [

m]

GPS/IMU

RTK

IMU only

~10m position error with

tactical grade IMU

Next step: GNSS / IMU / speed log

integration

- tightly coupled IMU / GNSS stand alone

-1 min GNSS outage

Accuracy estimation


1105 1110 1115 1120 1125 11300

5

10

15

20

25

30

35

Minutes of Day (minutes)

HPL [meters]

Horizontal Estimation Error (95%) [meters]

Horizontal Real Error [meters]

Number of Visible Satellites

Num

be

r o

f sa

telli

tes

15

10

5

Ho

rizo

nta

l e

rro

r [m

]

0

- adaptation of existing RAIM algorithm

(developed for aviation sector) to

maritime requirements

IMO

A.915(22)

Alert Limit

GPS single frequency stand alone positioning


PNT Unit interface

Open question:

Input interface - accuracy, integrity, continuity, availability for all PNT paramter

depended on the operational region

How this information about current operational region is transferred to PNT Module?

- ENC layer ? Output interface: - What integrity information should be delivered how?

www.DLR.de • Chart 14 > IALA Beacon DGNSS Monitoring Service > D. Minkwitz & MVT-Team • Date

Currently available MGBAS Services at Research Port

Rostock for Validation of aboard PNT-unit

RTCM Messages

via Radio Modem

Corrections

Information

Inte

grity


MGBAS: RTK Services

Goal: fulfill IMO’s port requirements regarding

accuracy, integrity, continuity and availability

Status:

two GPS-based RTK services

GALILEO-based and multi-GNSS services

in preparation

Minimum Requirements on Future GNSS Extract of IMO A.915(22)


MGBAS: IALA Beacon Monitoring Service

DGNSS Station (ID: 761) MGBAS as integrity monitor for RTCM2 messages

Assessment of IALA beacon DGNSS corrections as backup

for RTK services

2.55 2.6 2.65 2.7 2.75 2.8 2.85

x 104

0

2

4

6

8

10

12

14

16

18

Hour 7 to 8, DOY 54 Year 2012

GPS Day Seconds

3D

Positio

n E

rror

[m]

no corrections

RTCM2 corrections of Groß Mohrdorf


Summary

- Initial realization of a sensor fusion based PNT Unit

=> improved integrity monitoring incl. accuracy estimation

=> IMU contingency functionality

- Open questions:

- clear definition of user level integrity

- input: operational region

- output: HMI for integrity information

- Shore base services at Research Port Rostock

- MGBAS (RTK) service for high precision application

- IALA Beacon monitor

resilient pnt: from pnt-unit concept to first realization · • chart 1 >resilient pnt: from...

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