11

ANAN APPROACH APPROACH TOTODEVELOPDEVELOPMENTMENT OFOF

VIRTUAL DGPS VIRTUAL DGPS NETWORKNETWORKSS

Miroslav Miroslav J. J. Tsvetkov,Tsvetkov,

Kosta I. IvanovKosta I. Ivanov

Naval AcademyNaval Academy, Varna, Bulgaria, Varna, Bulgaria

UNCLASSIFIED

22

DGPS Coverage over Mediterranean and Black Sea DGPS Coverage over Mediterranean and Black Sea

Region - Region - February 2008February 2008

Red colorRed color – Active DGPS Radiobeacons; – Active DGPS Radiobeacons;Green colorGreen color – Not Active DGPS Radiobeacons (proposed, planed or tested); – Not Active DGPS Radiobeacons (proposed, planed or tested);

UNCLASSIFIED

33

Only 7 DGPS Radiobeacons are Active over 2.5 Only 7 DGPS Radiobeacons are Active over 2.5 millions kmmillions km22

DGPS Coverage over Mediterranean and Black Sea DGPS Coverage over Mediterranean and Black Sea

Region - Region - February 2008February 2008

UNCLASSIFIED

44

The accuracy of GNSSThe accuracy of GNSS

NavstarNavstar

36 meters horizontal accuracy at the 95% 36 meters horizontal accuracy at the 95% confidential level (2drms)confidential level (2drms)

77 meters vertical accuracy at the 95% 77 meters vertical accuracy at the 95% confidential level (2drms)confidential level (2drms)

GLONASSGLONASS

similar and sometimes bettersimilar and sometimes better

UNCLASSIFIED

55

Maritime User NeedsMaritime User Needs

International Maritime Organization (IMO) International Maritime Organization (IMO) Resolution A.915(22)Resolution A.915(22)

US Department of Defense and US US Department of Defense and US Department of TransportationDepartment of Transportation

“ “2001 Federal Radionavigation Systems” 2001 Federal Radionavigation Systems” (FRS)(FRS)

UNCLASSIFIED

66

Table 1 - Maritime User NeedsTable 1 - Maritime User Needs

Source Phase of navigation Accuracy required

(2drms) GNSS

IMO

Rez.А.915(22)

App. 2

Ocean, Coastal, Port and restricted waters,

Inland waterways

horizontal

10 mDoes not provide

IMO

Rez.А.915(22)

App. 3

Search and rescue, Oceanography, Fisheries, Recreation and leisure

horizontal

10 mDoes not provide

US

FRS

Inland waterway:

– Recreational boats & smaller vessels

– All ships and tows

horizontal

5 – 10 m

2 – 5 m

Does not provide

US

FRS

Harbor entrance and approach:

– All ships

– Resource exploration

horizontal

8 – 20 m

1 – 5 m

Does not provide

US

FRS

Coastal – All Ships

Ocean – All Ships

460 – 3700 m

3700 – 7400 mProvide

UNCLASSIFIED

77

Augmentation SystemsAugmentation Systems

wide area (WAAS, EGNOS, MSAS)wide area (WAAS, EGNOS, MSAS)

regional (SkyFix, StarFix, Eurofix, GRAS) regional (SkyFix, StarFix, Eurofix, GRAS)

local (maritime, aeronautical, geodetical)local (maritime, aeronautical, geodetical)

The best accuracy is achieved when using The best accuracy is achieved when using data from a local reference station situated data from a local reference station situated

near the user.near the user.

UNCLASSIFIED

88

Virtual Reference Station (VRS)Virtual Reference Station (VRS)

UNCLASSIFIED

99

User Effective Range Error (UERE)User Effective Range Error (UERE)

(3)

Estimated Position Error (EPE)Estimated Position Error (EPE)

(4)

Pseudorange Error BudgetPseudorange Error Budget

UNCLASSIFIED

User Range Error (URE)User Range Error (URE) URE = URE = ΔΔION + ION + ΔΔTRO + TRO + ΔΔSVSV (1)(1)User Equipment ErrorUser Equipment Error (UEE)(UEE)UEE = UEE = ΔΔMP + MP + ΔΔRR (2)(2)

2 2( )UERE URE UEE

(2 ) 2. .drmsEPE HDOPUERE

1010

OUR APPROACHOUR APPROACH

Reduce the Reduce the User Range ErrorUser Range Error (URE)(URE)

Calculate Calculate ΔΔIONION

(5)(5)

Calculate Calculate ΔΔTROTRO

(6)(6)

Calculate Calculate ΔΔSVSV

(7)(7)

2

1[ ] 40,25. .

cos 'ION

VTECm

f z

UNCLASSIFIED

[ ] . .TRO H Wm ZHDMF ZWDMF

2 2 2[ ] ( ) ( ) ( ) .SV eph IGS eph IGS eph IGS SVm x x y y z z c t

1111

Virtual Reference System ModelVirtual Reference System ModelStructural DiagramStructural Diagram

UNCLASSIFIED

1212

EXPERIMENTEXPERIMENT

• Date – 12.02.2008Date – 12.02.2008• Duration – 24 hoursDuration – 24 hours• Meteorological Data from Met.St. Meteorological Data from Met.St.

Varna,Varna,Bulgaria (WMO number 15552)Bulgaria (WMO number 15552)

• PC with MatLab and Internet PC with MatLab and Internet ConnectionConnection

• TransmitterTransmitter • DGPS ReceiverDGPS Receiver • GPS ReceiverGPS Receiver • Laptop Laptop

UNCLASSIFIED

1313

RESULTSRESULTS 86400 position reports from GPS Receiver have 86400 position reports from GPS Receiver have

been recorded (24 hours every second).been recorded (24 hours every second). Best accuracy has been achieved with using Best accuracy has been achieved with using

Hopfield’s troposphere model and Black’s Hopfield’s troposphere model and Black’s mapping function.mapping function.

Diagrams of the Diagrams of the horizontal accuracyhorizontal accuracy alternation alternation during experiment are shown on the next three during experiment are shown on the next three

slides.slides.

On the abscissa is plotted On the abscissa is plotted time (UTC)time (UTC) and on the and on the ordinate is plotted the value of ordinate is plotted the value of Circular Error Circular Error

Probable (CEP)Probable (CEP) in meters. in meters.

UNCLASSIFIED

1414

Green colorGreen color – Actual values of CEP – Actual values of CEPRed curveRed curve – Average values of CEP – Average values of CEP

CEP is alternating betweenCEP is alternating between 1,22 1,22 m andm and 1,55 1,55mm

in other words in other words the average HORIZONTAL ACCURACY at 95% the average HORIZONTAL ACCURACY at 95% confidence levelconfidence level ( (22drmsdrms))

is alternated between is alternated between 2,932,93 m and 3 m and 3,,73 m73 m

Accuracy AlternationAccuracy Alternationfor 30 minutes time intervalfor 30 minutes time interval

UNCLASSIFIED

1515

Accuracy AlternationAccuracy Alternationfor 2 hours time Intervalfor 2 hours time Interval

Green colorGreen color – Actual values of CEP – Actual values of CEPRed curveRed curve – Average values of CEP – Average values of CEP

The average HORIZONTAL ACCURACY at 95% confidence level The average HORIZONTAL ACCURACY at 95% confidence level ((22drms) for this period alternated drms) for this period alternated

between between 33,,84 84 m and 4m and 4,,6666 m. m.

UNCLASSIFIED

1616

Green colorGreen color – Actual values of CEP – Actual values of CEPRed curveRed curve – Average values of CEP – Average values of CEP

The average HORIZONTAL ACCURACY at 95% confidence level The average HORIZONTAL ACCURACY at 95% confidence level ((22drms) for this perioddrms) for this period

alternated between alternated between 22,,98 98 m and 4m and 4,,0606 m. m.

Accuracy AlternationAccuracy Alternationfor 30 minutes time intervalfor 30 minutes time interval

UNCLASSIFIED

1717

CONCLUSIONCONCLUSION

For period of 24 hours the For period of 24 hours the worst horizontal worst horizontal accuracyaccuracy at 95% confidence level is at 95% confidence level is

4,66 meters4,66 meters

UNCLASSIFIED

1818

THE MAJOR ADVANTAGES ARETHE MAJOR ADVANTAGES ARE

provide to maritime GPS users twice better provide to maritime GPS users twice better accuracy than the one required by IMO and accuracy than the one required by IMO and US;US;

cost effective;cost effective; independent of real reference stations;independent of real reference stations; no need to be stationary, can be mounted on no need to be stationary, can be mounted on

ship’s bridge;ship’s bridge; can establish and supply several Virtual can establish and supply several Virtual

Reference Stations simultaneously;Reference Stations simultaneously;

UNCLASSIFIED

1919

EXAMPLES OF USAGEEXAMPLES OF USAGE

The first example presents the potential of The first example presents the potential of the proposed model to establish a network the proposed model to establish a network or networks of virtual reference systems to or networks of virtual reference systems to provide high accuracy over a fixed sea provide high accuracy over a fixed sea areaarea

The second example presents the mobility The second example presents the mobility of the virtual reference systemof the virtual reference system

UNCLASSIFIED

2020UNCLASSIFIED

2121UNCLASSIFIED

2222UNCLASSIFIED

2323UNCLASSIFIED

2424UNCLASSIFIED

2525UNCLASSIFIED