Vertical GPS Heights

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Vertical GPSVertical GPSheightsheights

..

A Progression dissertation reportA Progression dissertation report

Victoria hardy.Victoria hardy.


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IntroductionIntroduction

3rd Year Hydrography.

Advisor: Victor Abbott,

Project titleProj

ect title

An investigation into the accuracy of vertical

static GPS


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Why?Why

?

Placement. June 04 - June 05.

Gardline Surveys.

Tides Survey, MBES survey, Debris search


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Background Theory.Backg

round Theory.

History of positioning.

Old techniques e.g. level

and theodlitie

Less accurate.

Vast improvements inpositioning since 1960s

Source Marek Zeibart2003Source Marek Zeibart2003


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Why is accurate height important?Why

is accurate height important?Why

is accurate height important?Why

is accurate height important?

Why

Accurate

mapping

Allows

precision

building

Air craft

flightPostioning


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Reference framesReference frames

Accurate height needs an accurate datum

Ordnance datum Liverpool 19th century

Ordnance datum Newlyn 20th

century More accurate

Used as national vertical reference frame

Creation of national wide bench mark system


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Development of positioning.Development of positioning.

WW2 V2 rocket. Satellite technology develops

Transit system 1964 Used Doppler effect

Magnitude change in frequency+ S.V orbit info+ time =

position

Source Space policyproject 2005


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Global Positioning SystemGlobal Positioning System

BeginningsBeginningsGlobal Positioning SystemEstablished 1980sCompleted in March 1994.

24 hour position:

Position = signal time x speed of light


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GPS- Set up.GPS- Set up.

Constellation 24satellites

Orbit 10,898 km aboveearth.

6 evenly spaced planes Inclined at 55 to

equator Orbital period 11 hours

56 minutesSource Garmin 2005


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Signal.Signal.

Pure sinusoidal waveTwo signals: L1 1575.42 MHz

L2 1227.60 Use L1 or both L1 and L2 Codes added to signal with info for a

fix

C/A Coarse acquisition code. 300mwavelength

(P) Precise Code: 30m wavelength


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GPS Monitoring.GPS Monitoring.


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PositioningPositioning

Capable of horizontaland vertical positioning

Vertical 1.5 times poorerthan horizontal.

Due to poor angle of cutUses range circles fromeach satellite. 4 required for a fix.

Plots position on anearth centred spheroid.

Source uk telemactic 2005


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ErrorsErrors

Receiver errors Clock error

Human errorMultipath

Atmospheric

Tropospheric Ionospheric


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GPS ModernisationGPS Modernisation

Galileo. European system. Launch 2008

30 SV

Civilian system 5 signals

GPS III Jan 1999 new signal L5

More SV 4000 billon dollar investment

SV talk to themselves

Source ESA 2004


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ExperimentExperiment

Initial experiment at Eyemouth. Data not compatible with software

New survey at Yarmouth usingcompany base station Unable to process data

Problems with data collection


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Problems

Set up

cable thru

window

Processing

cant process

hourly using

trimble

spilt 24 hour

file by rinex

program not

work

email trimble

program cant

do this

matlab not

work

Poor survey

records

not enough

onfo for

processing

lack of antenna

height


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SolutionSolution

Email experts.Talk to lecturer

Manually spilt the files in RINEX form.Use AUSPOS to process

Australian free GPS processing onlinesoftware

Allows triple differencing with base stationdata from Europe


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GPS vertical heights surveyGPS vertical heights survey

Survey location:Plymouth university

Fitzroy building Weather andionospheric datarecorded.

Details noted onprepared surveysheets

Source Ordnance Survey2004


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EquipmentEquipment

Trimble 4000 SSC Receiver height

108.522m

Log data every 5sec for 24 hours

Source Author All image


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ProcessingProcessing

Dat to RINEX

RINEX spilt into hourly segments

Segments upload into AUSPOSFinal results and report downloaded and

saved

Data put into tables and graphs


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Results- data collectedResults- data collected

Data

latitudelongitude

ellipsoid

height

base stations

used

spilt into

progressive

time segments


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LatitudeLatitude

32.7338

32.734


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LongitudeLongitude

19.7995

19.8


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Ellipsoid heightEllipsoid height

108.58

108.6


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Discussion-Ellipsoid heightDiscussion-Ellipsoid height

Increasing accuracy

No predictable trend in data set

No identifiable point where accuracy increase isminimal.

Final solution 108.512m 20cm difference

University base station 108.532m


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Factors which could haveFactors which could have

affected resultsaffected results

factors

affecting

results

Ionosphere

Long baseline

Troposphere

Receiver

model

Satellite

geometryProcessing

software

Line of sight


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Project improvementsProject improvements

Different receiver types.New systems. E.g. Galileo

Various locationsDifferent processing software.Local base stations


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ConclusionConclusion

No defined trend in 24 hour setNot possible to state a time in 24

hours when accuracy changeminimal

Further in depth study required


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References.References. AUSPOS(2005) RINEX processing service available atwww.ga.gov.au/geodesy/sgc/wwwgps Bannister A, Raymond S, Baker R (1998) Surveying 7th

edition Edinburgh Pearson education limited.

B.Hoffman_Wellenhof, H.Lichtenegger and J Collins

(2001) GPS theory and practice 5th revised editionNew York Springerwein

C. A, Erickson. P, Foster. J (2003) monitoring theionosphere with GPS. GPS world V14 N5 May 2003

C Tiberius and K de Jong (2002) Developments inglobal navigation satellite systems- GPSmodernisation, Galileo launched. N 104 hydrographicsociety

Garmin (2005) What is GPS. Available http://www.garmin.com/aboutGPS/ accessed

November 5th 2005
http://www.ga.gov.au/geodesy/sgc/wwwgpshttp://www.ga.gov.au/geodesy/sgc/wwwgps


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ReferenceReference

Mohinder G, Andrew A (2001) global positioningsystem inertial navigation and integration London

john Wiley and sons

Ordnance Survey (2004) questions on GPSavailable at www.gps.gov.uk/faq.asp#faq14Accessed June 30th 2004

Zilkoski , D, B and Hotheun D L (1989) GPSsatellite surveys and vertical control Journal of

surveying engineering. Vol 115 N2 Available atwww.ngs.noaa.gov/intiatives/heightmod/articles/jour.

(Accessed October 27th 2005)
http://www.gps.gov.uk/faq.asphttp://www.ngs.noaa.gov/intiatives/heightmod/articles/jour.surhttp://www.ngs.noaa.gov/intiatives/heightmod/articles/jour.surhttp://www.gps.gov.uk/faq.asp

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Vertical GPS Heights