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GGE2012 Advanced Surveying (Course Note)
Yong Yong- -Won Ahn / UniversityWon Ahn / University
Tutorials and Processingof GPS Survey Data
of New Brunswick, Canadaof New Brunswick, Canada
Yong-Won Ahn Department of Geodesy and Geomatics Engineering University of New Brunswick 1/00
Contents
Orbits (precise or broadcast) Data rate and observation span
Tutorials of GPS Survey
Elevation angle Points to be observed on your lab. Processing software and methodology Processing GPS data
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ppen x: ystem, e g t
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GPS measures ranges.
If a reference station is on a
Tutorials of GPS Survey
Recording GPS observation
known location then the rangecan be calculated.
The difference between themeasured and calculatedranges is measurement error.
The error measured at a
Error
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re erence stat on s s m ar tothe error measured by nearbyreceivers ( differentialapproach)
GPS Orbits Tutorials of GPS Survey
1. Broadcast orbit from GPS satellites ( Real-Time Processing)
2. IGS Products (In Near Real-Time Processing) The IGS (international GNSS service) collects, archives, and distributes GPSand GLONASS observation data sets of sufficient accuracy to meet the
objectives of a wide range of scientific and engineering applications andstudies. These data sets are analyzed and combined to form the IGSproducts.
IGS products support scientific activities such as improving and extendingthe International Terrestrial Reference Frame ( ITRF ) maintained by the
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International Earth Rotation and Reference Systems Service (IERS),monitoring deformations of the solid Earth and variations in the liquidEarth (sea level, ice sheets, etc.) and in Earth rotation, determining orbitsof scientific satellites, and monitoring the troposphere and ionosphere.
( http://igscb.jpl.nasa.gov/components/prods.html ) IGS: SOPAC, CDDIS, IGN, KASI US,France, and Korea
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GPS Orbits (in 2009)
Tutorials of GPS Survey
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Note: These values are differences from SLR measurements. Also, even if there isan errors, it can be minimized by differential techniques on GPS processing.
(accessed on21 March 2009)
GPS Orbits (in 2010, 2011) Tutorials of GPS Survey
Note: Compared thesewith last year,
1) All orbits are.
2) Clock errors are alsoimproved.
3) The improvementsare very beneficial inprecise pointpositioning.
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(accessed on22 March 2010 & 22 March 2011)
4) In your field surveydesigned, the broadcast,ultra-rapid or rapid orbit is fine .
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Gillin Hall (Control Point)
Tutorials of GPS SurveyExample
Kinesiology
Irving Lib.manhole
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SUBmanhole
Data Rates and Minimum Obs. TimeTutorials of GPS Survey
More data means more redundancy at least 5 secondsdata rate would be recommended. Normal value for the data
,depends on the observation time.
Minimum observation time? at least 30min, 45min
-- Hint: In principle, the position can be determined with oneepoch in terms of least square adjustment. We are dealing
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.equation, called integer ambiguity, which may need to bedetermined during the process.
Masking angle? 5 deg. (not suggested over 10 deg.)
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[Geodetic Software post mission, examples]
: Bernese GPS Software (from AIUB Astronomical Institute ofUniversity of Bern, Bern, Switzerland, Available for our GGE
Tutorials of GPS Survey
GPS Processing Software:
department, academic & commercial )
: GIPSY-OASIS II (from NASA JPL, free )
: GAMIT (from MIT), DIPOP (from UNB, free )
[Commercial Software post mission mostly, examples]
: TGO (Trimble Geomatics Office)
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, ,
: GrafNav (from NovAtel Inc., Calgary)
: MultiRef, FlyKin (from Geomatics Eng. at U of Calgary)
: UNB-RTK (from GGE), Precise Point Positioning ( free software, NRCan(Canada), Auto-GIPSY (NASA, ~free ), UNB-GAPS (UNB, free )) etc.
[Measurements from a GPS Rx, Trimble, Leica, or TOPCon receiver]
: C/A Code, L1 phase, (+ L2 phase, P2 code)
Tutorials of GPS SurveyGPS Processing Methodology
1. Short baseline case same atmosphere (at UNB campus )
: C/A and L1 code/carrier phase measurements
: Never use the L1 and L2 combination , e.g. ionosphere-free linearcombination due to the amplification of the noise.
: GGE2012 practice.
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2. Longer baseline case different atmosphere (over 10 km)
: Either C/A + L1 phase with the method of atmospheric error mitigation,or C/A + both L1 and L2 phase combination to mitigate errors mainlyby the ionosphere. Frequently, this combination is referred to asionosphere-free combination: GGE2013 practice.
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GPS Processing Introduction: TGO
: Post mission
Processing GPS Data
: Solutions are too optimistic (only mathematical correlation isconsidered)
: Limited analysis
: Commercial software can hardly guarantee the accuracy of less thancm from the true value in static mode. In a real-time mode or RTK mode,the achievable accuracy is lower. You must be very careful for this.
: For those who works or ma -matchin land ro ert mana ement
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, ,or low-precision GIS which dont need a high-precision application: For those who study for geodetic accuracy, please use other geodeticsoftware stated before.
GPS Recording in Field:
: One Zephyr/ZephyrGeodetic Antenna
Processing GPS Data
: One Trimble 5700 Rx
: One TSCe Controller
: One Triback
: One Tripod
: Cables (Coaxial to Rx,
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,
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GPS Data Preparation: : Not general scheme, only for Trimble Rx and Software related
: Download the *.dc controller files from controller using RS232 port
Processing GPS Data
Connectin Cable
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from TSCe toComputers COMport (or USB port)
GPS Data Preparation: Two Options
1. From TSCe Controller, you can download *.dc file*
Processing GPS Data
. .
2. Secondly, you can download raw data from flashcard in the receiver. These data sets should beconverted to the standard form. (preferred)
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GPS Data Preparation: : Once the cables are connected, then please launch the program, DataTransfer
: You also have to set u the PC communication in the TSCe controller to
Processing GPS Data
connect each other (between TSCe and Computer)
: If TSCe is ready to be connected, please choose the proper device andclick the connection button (see below)
: Once succeeded, you must add
the file and then choose
transfer all
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: *.dc file and *.dat will be
downloaded.
GPS Data Preparation:
: Another way to download the GPS data is from the CF (compact flash)memory card directly.
Processing GPS Data
.Also, it will minimize your mistake of the controller settings. Strangething Ive found is that once the controller is close earlier or once youfailed to end the survey on the controller, the download data from thecontroller had a problem. It failed to be downloaded all spans.: Please follow this way at least for the Trimble Rx and TSCe controllerfor our GPS lab.
Download the raw data in *.T01 ormat rom CF memor card
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Transfer from the raw format (*.T01) to *.dat with the followingprogram: runpkr00.exe
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GPS Data Preparation: : Download the program, called R-Utilities from
http://facility.unavco.org/software/download_transfer/trimble/trimble.
Processing GPS Data
html
: use the following sentence to decode the *.t01 file
: runpkr00 -d -tt01 file_name.t01 file_name.dat
(You may also download the program from the course Blackboard.Please try to find the program yourself first.)
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accessed on 21 March,2011)
Important Setup for TGO:
1. Please find the attached the file (Current.csd) in Blackboard whichyou are going to use to set up NB Double Stereographic Projectionwith NAD83 CSRS datum . You should copy this file to the following
Processing GPS Data
directory or the corresponding directory TGO is installed.
c:\Program files\Common files\Trimble\Geodata
2. After you copy it, go to TGO and follow the below instructions:
File Project Properties Coordinate System
Coordinate S stem Settin s Chan e
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Coordinate System and Zone ( Canada and Plane Rectangular)
No Geoid Model Finish Apply
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You must see thefollowing on theproject properties.
Processing GPS Data
If different, pleasesee previous fileand find out theproblem.
If this is different,
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your entireproject forGGE2012 andGGE2013 will bewrong.
Go to
File New
make ro ect
Processing GPS Data
name
( should be metricsystem )
OK
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Go to
File Import GPS data file
Processing GPS Data
. a
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You may see the following file lists on DAT check-in. Most importantparts are the antenna height, antenna types, and reference points ofantenna (either bottom of notch, top of notch, or antenna phasecenter for each antenna which ou used . You HAVE TO in ut the
Processing GPS Data
corresponding values on each field EXACTLY. Most important !!!
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This includes: Antenna Height, Antenna Type, andAntenna Reference Point (Always use the PhaseCenter and input your hand-calculated phasecenter value for your antenna for exercise!!!
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Now, you will seethe correspondingnetwork diagramfor your GPS
Processing GPS Data
observations
(Left is just anexample fromGGE2013 surveypracticum II)
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Go toSurveying GPS BaselineProcessing
Processing GPS Data
Style
Edit Selectmask angle to
5 deg. Orbit(Eitherbroadcast orprecise) Fixed t e
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solution
Advanced please see thedetails of eachtab.
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Go to Surveying GPS BaselineProcessing (F9): itwill process your
Processing GPS Data
selected baselines.
After finished, youwill see the similarresult like the left.
Please save the fileand see all thedetails from the
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.
: Make a project andcopy all *.dat tocheckin directory.
Processing GPS DataCycle Slip Manipulation
: View Timeline
(check the time line
and then decide iftherere any data toremove or not to beprocessed, minor!)
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: Cycle slip elimination(check the jumps anddeactivate those)
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GPS Network Adjustment: Fixed Control Point : Bring all GPS data
: Check the antenna height or put the correct APC of theantenna
Processing GPS Data
: Click Process button (will take time)
: Baselines can be seen (as white line) in TGO
: Adjustment will be done by selecting the baselines that makea triangle network
: Selected and then click the Adjust button
: Re ort Network Ad ustment Re ort
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: Analysis the results
Note: Fixed Point (Gillin Hall): From GPS Lab.
(Applied to TGO and adjusted based on this)
Gillin Hall ( NAD83 CSRS )
Lat: 45 57 0.9478
Lon: 66 38 32.2343
Hgt: 18.362 m
gate
After processed thebaselinesuccessfully, go toAdjustment. Check
Processing GPS Data
Adjust to NAD 1983(Canada)
Adjustment Points you mustfix Gillen Hallwith the
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provided.
Adjustment Adjustment (F10)
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After the adjustment, you can find the final adjusted coordinatesfrom the adjustment report.
From the report, your final horizontal coordinates will be one like
Processing GPS Data
.fixed or not.
Adjusted Coordinates
point name Lat. N Err Long. E Err Ell.Hgt. H Error Fixed
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These heights are the ellipsoidal ones: You have tochange them to the orthometric height .
[Check]
: SkyPlot
Processing GPS Data: Review
: DOP Check
(must be pre-
determined)
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Antenna Height (Pl. use APC)
Processing GPS Data: Review
: Please calculate antenna
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p ase center va uesprovided on the back of theantenna.
: Zephyr Geodetic Antenna
Antenna Height (Pl. use APC) Processing GPS Data: Review
: Please calculate antenna
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provided on the back of theantenna.
: Zephyr Antenna
. cm
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Antenna Height (Pl. use APC)
Processing GPS Data: Review
: Please calculate antenna
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provided on the back of theantenna.
: Micro Centered L1/L2
TIP: Concerned about geometry andvisibility?
: Please use the Plannin
Processing GPS Data: Review
Tool before you startsurveying!
: Can you find any bad timefor your survey schedulefrom the right figure?
: You can check them in anytime and any location in the
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world if you provide theproper almanac to thesoftware (its in the TGOutilities!)
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TIP: Need a pre-analysis in detail?
: Please use TEQC quality check program provided by UNAVCO
Processing GPS Data: Review
: You can download it from the link
http://facility.unavco.org/software/teqc/teqc.html
: It can manipulate, concatenate, pre-analyze, pre-processing GPS,GLONASS, SBAS
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[1] Leick, A., 1995, GPS Satellite Surveying, 2nd Ed. John Wiley& Sons, New York.
References
an, ttp: www.geo .nrcan.gc.ca too s-out s gps _e.p p
[3] SNB, http://www.snb.ca/ , Service of New Brunswick.
[4] Lecture Note GGE2012, 2007, by Prof. Peter Dare.
[5] Hofmann-Wellenhof. B., H. Lichtenegger and J. Collins, 1998,GPS Theory and Practice. 4th Ed., Springer-Verlag, New York.
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[6] Kavanagh, 2006, Surveying: Principles and Application, 6th Ed. New Jersey, Prentice Hall.
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Earth-Centered Earth-Fixed (ECEF) CoordinateSystem For the purpose of computing the position of a GPS Receiver
Rotate with the Earth
WGS84 System
The Characteristics of ECEF Originate at the center of the Earth xy -plane : coincide with the Earths equatorial plane +x -axis : Point in the direction of 0 longitude +y -axis : 90 E longitude +z -axis : Normal to the equatorial plane in the direction
of the geographical north pole
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The satellite position & velocity vectors must be available in theECEF for GPS navigation problem
In the case of GPS positioning, Cartesian coordinates ( X,Y,Z ) of theusers receiver are computed
World Geodetic System (WGS84 ) Standard physical model of the Earth for GPS
The Characteristics of WGS84
WGS84 System
a : 6378.137 km = Mean equatorial radius b : 6,356.7523142 km
e : Eccentricity of Earth Ellipsoid = 0.0818 c : speed of light = 299,792.458 km/s f : flattening = 1 - b / a e : second eccentricity = eb / a
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= .
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Geodetic Coordinates System ECEF coordinate with the reference ellipsoid (for
example WGS84) called Geodetic coordinate So called Geographic coordinate system
WGS84 System
Geodetic longitude ( ) The angle between the user and the x -axis measured in the
xy -plane Geodetic latitude ( )
The angle between the ellipsoid normal vector & projectionof it into the equatorial plane
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Relative to the WGS84 ellipsoid not to the geoid Minimum distance between the user and the reference
ellipsoid(i.e. ellipsoid normal)
GPS HeightHeight
- Geodetic (Ellipsoidal) Height; h: The height above the ellipsoid. Ellipsoidal height is geometric, not a physical
parameter and is what is given by the GPS technique.
- Orthometric Height; H: The height above MSL. Orthometric height is a physical parameter and is what
is given by most conventional surveying techniques. It is the level surface thata body of water will conform to. In this section (H) is obtained using the GPSobserved ellipsoidal height (h) and correcting it with the Geoid/Ellipsoidseparation (N) and the geoid model. For all pillar type HPN this value can becompared with the leveled height.
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- Geoid ellipsoidal separation (N):: Is the distance between the ellipsoid and geoid at a specific point and is also
known as the Geoid Undulation. The separation added to the orthometric (sealevel) height (H), results in the ellipsoid height (h). The following formulae is of
Height
GPS Height
particular importance with the use of GPS.
h = H + N
whereh = is the ellipsoidal height
(height usually obtained with GPS)
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H = is the orthometric height (sea-level)N = is the geoid ellipsoidal separation
GPS-H:
GPS Height Transformation Packages .
Height GPS Height
http://www.geod.nrcan.gc.ca/tools-outils/gpsh_e.php
Online or Offline programs are provided. Offlineprogram, called gpsh-e.zip released on Nov. 2001,
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is Win16 environment. Please check your computerto install it.
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Height Geoid Model:
CGG2000 CanadianGravimetric Geoidmodel 2000 is a
GPS Height
scientific model of thegeoid for NorthAmerica from gravitydata up to 2000.
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The Geoid model contributes to the vertical component of thereference system so that ellipsoidal GPS heights can beconverted to orthometric elevations for practical uses.
Height GPS Height
The real challenge lies in knowing the relationship betweenthe ellipsoid and the geoid. Once we determine the differencebetween these two surfaces, called the "geoid-ellipsoid
separation" or "geoidal height", at a given point, we can thenapply the geoidal height to our GPS height measurement toget the mean sea level elevation. (from NRCan website)
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Online Service (from NRCan website)
http://www.geod.nrcan.gc.ca/apps/gpsh/gpsh_e.php
Height
GPS Height
Please inputcoordinates manually
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