Post on 07-Dec-2014
description
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
CyScan Positioning System
BASELINE
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Powerful Rotating Pulsed Ranging Laser
Single Target Operation
Position and Heading from 2+ Targets
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Automatic Elevation Tracking
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RS485 Data Links
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Shuttle Tankers
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Cable Laying
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Possible Application Areas
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Dynamic wave motion compensation/built-in VRU
Elevation tracking for draft change compensation
Low cost and maintenance/cheap passive targets
Interfaces easily to modern DP systems
High immunity to ambient or bright lights
Survives temporary obstruction of one or more targets
Ignores spurious or erroneous reflections
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Special Competitive Features (2)
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2nd Generation Marine Navigation System