Typical DP system sensorsDGPS

COMPUTER CYSCAN

TAUTWIRE POSITION

MEASURING SYSTEM

WEIGHTACOUSTIC

BEACON

ACOUSTIC

POSITION

MEASURING

SYSTEM

SURFACE

POSITION

MEASURING

SYSTEM

Taut Wire

Artemis

Artemis

AZIMUTH

BEARING

RANGE

ANTENNA

LOCKED

Fixed Station - Calibration

North

FIX

North

Visual reference point

A Telescope, mounted on

top of the fixed antenna, is used

Range and bearing measurements

North

FIX

Azimuth

MOB

Distance

North

Azimuth

True bearing = Azimuth + 180°

Heading presented on the EOP

North

FIX

Azimuth

MOB

Distance

North

Azimuth

Relative Mobile Antenna Bearing

North

Heading

Heading = Azimuth + 180° - Relative Mobile Antenna Bearing

Artemis beacon ARTEMIS BEACON

BASE

POSITION

ARTEMIS

BEACON

ARTEMIS MICROWAVE LINK

THE BEACON IS SIMPLYA TRANSPONDER. NO

BEARING DATA TRANSMITTED

ARTEMIS

MOBILE

ANTENNA

SHUTTLE TANKER

DURING APPROACH

OFFSHORE LOADING

TERMINAL WITH

ROTATING TURNTABLE

BEARING MEASURED

AT MOBILE ANTENNA

TELEMETRY LINK ALLOWS TURNTABLE AZIMUTH TO BE

TRANSMITTED TO THE VESSEL SUCH THAT BEACON OFFSET

CAN BE COMPENSATED FOR, CORRECTING THE RANGE TO

THE BASE LOCATION

Range and bearing measurements - Beacon

Beacon

MOB

Relative Mobile Antenna Bearing

North

Gyro

True Bearing = Gyro + Relative Mobile Antenna Bearing

Distance

Dip Zones

REFLECTED

LINK

FIXED ANTENNADIRECT MICROWAVE LINK

AT SPECIFIC RANGES, THE DIRECT LINK

WILL INTERFERE WITH THE SURFACE

REFLECTED SIGNAL CAUSING LOSS

OF SIGNAL

Dip Zones

PRODUCT

H1 x H2

H1 =

Mobile

antenna

height

H2 =

Fixed

antenna

height

800

700

600

500

400

300

DISTANCE (metres)

6000 10000 14000 18000 22000 26000 30000

6000 10000 14000 18000 22000 26000 30000

DIP

ZONES

Vertical beamwidth

ARTEMIS ACQUIREDNORMALLY ATLONG RANGE

ARTEMIS LOST DUETO VERTICAL BEAMWIDTHAT CLOSE RANGE

ARTEMISFIXEDSTATION

MOBILEARTEMISANTENNA

MOBILE AND FIXEDANTENNAE AT

DIFFERENT HEIGHTS

Artemis alarms, warningand messages on the SDP:

Artemis basic unit timeout

Artemis system communication error

Artemis system out of range

Artemis system telegram error

Accuracy and specification:

Distance accuracy = 1m

Azimuth accuracy = 0.02°

Beacon accuracy = using gyro accuracy = approximately: 0.5°

Artemis - advantages and disadvantages

Advantages:

• Long range system - compared with HPR, Fanbeam, LTW

• High accuracy

Disadvantages:

• Affected by heavy rain and snow in same way as a radar

• Line of sight problems

• Interference from 3 cm radar

• Requires personnel to set up the fix station

System1:Pair “0” = Mobile 9200 - Fix 9230 or Pair “2” = Mobile 9230 - Fix 9200

System 2:Pair “1” = Mobile 9300 - Fix 9270 or Pair “3” = Mobile 9270 - Fix 9300

More users at one site

More users at one site

GPS FundamentalsGPS & GLONASS Specifications

GPS GLONASSNumber of Satellites 24 24

Number of Orbital Planes 6 3

Satellites Per Plane 4 8

Orbital Inclination 55 deg. 64.8 deg.

Orbital Radius 26.560 km 25.510 km

Orbital Period 11h 58m 11h 15m

L1 Frequency 1575.42 MHz 1602+K*9/16 K=[-7,24] MHz

L2 Frequency 1227.60 MHz 1246+K*7/16 K=[-7,24] MHz

Time Reference UTC UTC

(US Naval Observatory) (Sovjet Union)

Geodetic Datum WGS 84 PZ-90

The number of available GPS satellites varies around 27-29 due to longer lifetime

than expected. The GLONASS satellite service has not been able to provide a

complete constellation due to lack of satellite replacements and fundings.

Navigation Global Positioning System

US DoD system

21 +3 satellites

Satellite Altitude of 20,200 km

Orbit Separation of 60 degrees

6 Orbit Planes

12 hour Satellite Orbit

2 frequencies – C/A code and P-code

GPS

SIX

ORBITS

FOUR

SATELLITES

PER ORBIT

FOURSATELLITES

IN VIEW

Signal division

FDMA – Frequency Division Multiple Access

TDMA – Time Division Multiple Access

CDMA – Code Division Multiple Access

FDMA-CDMA – Frequency + Code Division Multiple Access

GPS Pseudo-Range

Tropospheric

Ionospheric

Receiver clock

Satellite clock

Orbital

Multipath, receiver noise, antenna setup

The Atomic clock from the satellite is compared with the clock onboard or at the reference station, this produces the pseudo range from which a position is calculated.

Tropospheric

Ionospheric

Receiver clock

Satellite clock

Orbital

Multipath, receiver noise, antenna setup

GPS position computation

Basic Principles of Positioning with GPS

Basic Principles of Positioning with GPS

GPS Accuraсy

Depends on:

Satellite Constellation Geometry

Satellite Orbit

Atmospheric Path Propagation

Clock Stability

Multipath Signals

Selective Availability

GPS FundamentalsGood DOP

Satellite range footprintUERE

UERE

Satellite

range

A C

D

B

The intersection area

(A-B-C-D) is the area

where it is most

propable that the

position solution lies

within.

Good DOP is when the intersection between ranges

from two (or several) satellites are perpendicular or

particularly well defined.

GPS FundamentalsPoor DOP

UERE

UERE

Satellite

range

Satellite range footprint

A

D

B

C

Poor DOP is when the

intersection between ranges

from two (or several)

satellites are not

perpendicular or

particularly well defined.

The intersection area (A-B-

C-D) is the area where it is

most propable that the

position solution lies within.

GPS FundamentalsGood & Poor DOP

Bull's eye plot of satellites in the sky

Good Dilution of Precision Poor Dilution of Precision

Elevation Mask (10 degrees)

GPS FundamentalsHow Positions are Computed

UERE

UERE

Satellite

range

Position accuracy is a function of how accurate ranges to the

individual satellites can be determined and how well the

satellites are distributed on the sky.

Position accuracy = UERE * DOP

GPS FundamentalsComputed Position Accuracy

Estimated SPS C/A-Code Pseudorange Error Budget

GPS

Segment Source Error Source 1 sigma Error (m)

Space Satellite clock stability 3,0

Satellite perturbations 1,0

Selective Availability -

Other 0,5

Control Ephemeris prediction error 4,2

Other 0,9

User Ionospheric delay 5,0

Tropospheric delay 1,5

Receiver noise & resolution 1,5

Multipath 2,5

Other 0,5

System UERE total (rss) 8,0

Actual HDOP 1,0

Position Accuracy (2-D, 67%) 8,0

Position Accuracy (2-D, 95%) 16,0

GPS FundamentalsComputed Position Accuracy

16 m (95% CEP)

A reported position with

accuracy number 16 m (95%

CEP) means that there is a 95%

probability that the next

horizontal position will be

inside a circle with radius 16

meters.

DOP - Dilution of Precision

Poor Geometry (High DOP number) Good Geometry (Low DOP number)

GDOP

VDOP

HDOP

PDOP

Acronym Type Position Component(s)

Geometric

Positional

Horizontal

Vertical

3D position & time

3D position

2D horizontal position

1D height

GPS Satellite

Monitor Stations

Colorado Springs

Hawaii

Ascension

Diego GarciaKwajalein

GPS Error Sources

Selective Availability

Deliberate Degradation of GPS Signals by DoD

Affects SPS Service –

Accuracy Reduced from 20m to 100m drms

• Errors Due To – clock bias

Reduction of GPS Position Error

A period from 01/05/2000 till 02/05/2000

Satellite Navigation System ”GLONASS”

24 satellites

3 Orbits

Orbit Height 19100 КМ

Inclination 64,8 °

Period: 11,26 hours

GLONASS’s Satellite

Main GLONASS satellite characteristics:

Weight – about 1300 kg;

Diametre – 2,35;

Length overall – 7,84m;

Width overall (with sun batteries ) -7,23m;

Data transfer speed on navigational channel –50bit/sec;

Received signal power - -156/-161 dBWt

GLONASS System Current State according to Almanac data

Number of GLONASS satellites/ coverage area

№/ plane 01 02 03 04 05 06 07 08

I - + + + + - + +

II - - - - - - - -

III + + - - + + + +

КНС ГЛОНАСС на 16.10.2007| Пл-ть 1/точка | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 |

| Номер частоты | 07 | -- | -- | 06 | -- | 01 | 05 | 06 |

|---------------- |----|----|----|----|----|----|----|----|

| Пл-ть 2/точка | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |

| Номер частоты | -- | 04 | -- | -- | -- | 04 | 00 | -- |

|---------------- |----|----|----|----|----|----|----|----|

| Пл-ть 3/точка | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 |

| Номер частоты | -- | -- | -- | -- | 08 | -- | -- | -- |

GPS System Current State according to Almanac data

Number of GPS satellites/ coverage area

№ / plane I II III IV V VI

1 + + + + + +

2 + + + + + +

3 + + + + + +

4 + + + + + +

5 + + + + + +

> 4 SV are visible

Visibility of SV 1-24

Coverage area for GLONASS with not less than 4 SV visible

Availabilityof GLONASS

Federal State Program for development of global navigation system

GLONASS system structure

Plan of satellite replenishmentfor GLONASS

Growth of GLONASS users

Galileo

30 Satellites at an Altitude of 23000 Kilometres

Accurate Survey References for Roads & Bridges

Available by 2010

Will Supply Real Time Data

How it works

It will be a civil system

GPS accuracy is about 30 metres

Galileo accuracy within 1 metre

No correction signal is required

Interoperable with GPS and Glonass

28.12.2005 GALILEO, Europe’s global satellite navigation system

is now a concrete reality. Today, the 600-Kilogram GIOVE-A satellite, manufactured by the British company Surrey Satellite Technology Limited, was placed in a 23,222 kilometres orbit by a Soyuz rocket from the Baikonur cosmodrome in Kazakhstan.

The GIOVE mission (Galileo In-Orbit Validation Element) comprises 2 satellites (GIOVE-A and B). GIOVE tests critical new technologies (such as the on-board atomic clocks, signal generator and user receivers) and validates the new features of the Galileo signal design, characterises the radiation environment of the Medium Earth Orbits (MEOs) planned for the Galileo satellites and secures access to the Galileo frequencies allocated by the International Telecommunications Union.

27.04.2008

A further step towards the deployment of Europe's Galileo global navigation satellite system was taken tonight, with the successful launch of ESA's second Galileo In-Orbit Validation Element (GIOVE-B) satellite, carrying the most accurate atomic clock ever flown into space.

The GIOVE-B satellite was lofted into a medium altitude orbit around the earth by a Soyuz/Fregat rocket departing from the Baikonur cosmodrome in Kazakhstan by launch operator Starsem. Lift-off occurred at 04:16 local time on 27 April (00:16 Central European Summer Time).

This 500 kg satellite was built by a European industrial team led by Astrium GmbH, with Thales Alenia Space performing integration and testing in Rome. Two years after the highly successful GIOVE-A mission, this latest satellite will continue the demonstration of critical technologies for the navigation payload of future operational Galileo satellites.

Like its predecessor, GIOVE-B carries two redundant small-size rubidium atomic clocks, each with a stability of 10 nanoseconds per day. But it also features an even more accurate payload: the Passive Hydrogen Maser (PHM), with stability better than 1 nanosecond per day. The first of its kind ever to be launched into space, this is now the most stable clock operating in earth orbit.

GALILEO

The Modernized L2 Civil SignalAfter years of preparation, modernization called for: implementing military (M) code on the L1 and L2 frequencies for the

Department of Defense (DoD) providing a new L5 frequency in an aeronautical radio navigation service

(ARNS) band with a signal structure designed to enhance aviation applications

adding the C/A code to L2.Implementation was underway when the System Program Director for the

GPS Joint Program Office (JPO) asked whether it was wise simply toreplicate the 20th-century C/A code in a 21st-century “modernized”GPS.

Responding to this challenge, a truly modern L2 civil (L2C) signal wasdesigned in a remarkably short time to meet a much wider range ofapplications. The first launch of a Block IIR-M satellite in 2003 willcarry the new signal, as will all subsequent GPS satellites. As a result,civil GPS product designers eventually will have at least three ratherdifferent types of GPS signals to choose from. It also would be desirablefor GPS III to add a modern civil signal to L1, further increasing thenumber of design choices. Depending on the application, designers willbe able to select signals based on power, center frequency, code clockrate, signal bandwidth, code length, correlation properties, thresholdperformance, interference protection, and so on.

The Modernized L2 Civil Signal

DGPS system Configuration

WGS 84

REF

POSITION

REFERENCE

STATION

WGS 84

REF

POSITION

CORRECTIONSIGNAL

Relative DGPS, DARPS- Differential and Relative Positioning

RELATIVE GPS

SHUTTLE TANKER

UHF

LINKSFPSO

Differentialonnection

Sky Fix System Overview

Why DGPS for DP Vessels

Globally available 24 hours/day

Not limited by geographic location

Not effected by weather, e.g. Radio Nav

Performance independent of water depth

Acoustics

Not effected by dynamic motion

e.g. Taut Wire Weights

Acoustic Interference – Thruster Wash

What is DGPS

• Basic Concept

• Observe all satellites at fixed reference station

• Reference station position is known very accurately

• Reference station measures PR to all satellites

• Satellites broadcast their positions in message

• Reference station compares observed and calculated PR

• Assumes all errors are range errors

• Computes and transmits DGPS correction signals

DGPS Networks

Defined by:

Single Reference Station Solutions

Multi-Reference Station Solutions

Multi-Reference Station Network Solutions – also termed VBS (Virtual Base Station)

Correction Message Data Link:

• MF

• HF

• UHF/VHF

• Inmarsat A/B/M

• Eutelsat/Spot

DGPS Configurations

Direct Injection Solution

COMMUNICATION

RECEIVER

DGPS

DEMODULATOR

ON-LINE

NAVIGATOR

DGPS

RECEIVER

DGPS Configurations

Multi-Ref DGPS Solution

COMMUNICATION

RECEIVER

DGPS

DEMODULATOR

ON-LINE

NAVIGATORDGPS

MULTI-REF

PROCESSOR

DGPS

RECEIVER

6 World-Wide Coverage

DGPS North Sea

DGPS Gulf of Mexico

FANBEAM

RANGE

BEARING

FANBEAM

Fun beam screen

FANBEAM

28V POWER SUPPLY

A C

IMPUT

DECK CABLE

CURRENT LOOP

CONVERTOR OR UCU

TO DP CONSOLE OR

SEISMIC SOFTWARE

POWER CABLE

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