21.lecture110324 gge2012 gps04 tutorial byahn 2pages

8/12/2019 21.Lecture110324 GGE2012 GPS04 Tutorial ByAhn 2pages

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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


ppen x: ystem, e g t


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GPS measures ranges.

If a reference station is on a


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


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


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)



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.


(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


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


.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


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)


, ,

: 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.


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


, ,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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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


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


: *.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


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.)


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


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,


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


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 !!!


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)


Go toSurveying GPS BaselineProcessing

Processing GPS Data

Style

Edit Selectmask angle to

5 deg. Orbit(Eitherbroadcast orprecise) Fixed t e


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


.

: 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!)


: 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


: 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


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


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)


: Please calculate antenna


p ase center va uesprovided on the back of theantenna.

: Zephyr Geodetic Antenna

Antenna Height (Pl. use APC) Processing GPS Data: Review



provided on the back of theantenna.

: Zephyr Antenna

. cm


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Antenna Height (Pl. use APC)




provided on the back of theantenna.

: Micro Centered L1/L2

TIP: Concerned about geometry andvisibility?

: Please use the Plannin


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


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


: 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


[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.


[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


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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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


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)


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,


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.


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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