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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/wwwgps8/14/2019 Vertical GPS Heights
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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.aspTop Related