1. Surveying II UNIT IV
GPS SURVEYING

2. Basic concepts – Different segments – space control and user segments – satellite configuration- signal structure – orbit determination and representation – antispoofing – and selective availability – Task control segment -Hand held and Geodetic receivers – data processing – Traversing – and triangulation
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4. parts of system include: space (GPS satellite vehciles, or SVs)
control (tracking stations)
users
first one launched in 1978
….June 26, 1993
Air Force launched 24th SV
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5. Design Objectives of GPS
Suitable for different platforms: aircraft, ship, land-based and space (missiles and satellites),
Ability to handle a wide variety of dynamics,
Real-time positioning, velocity and time determination capability to an appropriate accuracy,
Single global geodetic datum (reference system) for defining position,
Differential accuracy standards: highest accuracy to be restricted to a certain class of authorized users,
Resistant to jamming (intentional and unintentional),
Redundancy provisions to ensure the survivability of the system,
Passive positioning system that does not require the transmission of signals from the user to the satellite(s),
Ability to provide the service to an unlimited number of users and world-wide coverage
Low cost, low power, therefore highly complex satellite segment,
Total replacement of the Transit 1 satellite and other terrestrial navigation aid systems.
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6. Signal Measurement Techniques Geocentric & geodetic Reference Systems
Introduction
Signal Measurement Techniques
Geocentric & geodetic Reference Systems
Time Systems
Satellite Configuration
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7. Principles Of Global Positioning System (GPS) What is GPS?
The GPS reference system
The GPS system components
The space segment
The control segment
The user segment
GPS positioning principles
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9. Basic functions of satellites include:
Space Segment
Constitutes satellite constellation which downlinks data including coded ranging signals, position information, atmospheric data, and almanac (data about approximate orbit information of all satellites).
Basic functions of satellites include:
Receive and store information transmitted by the control station
Perform limited data processing by its own computer
Maintain very accurate time by means of onboard 2 cesium and 2 rubidium oscillators
Transmit information to the user by the signal message
Maneuver to position in space controlled by the control segment
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10. Figure 5.1 GPS constellation consisting of six orbital planes with four satellites in each plane. Each satellite is identified with a two-character code: a letter identifies the orbital plane (A through F) and a number identifies the satellite number in the plane (Enge and Misra, 1999)
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12. Control Segment I
It consists of 5 tracking station to collect data based on observing satellite in their orbits. Tracking is executed with two frequency receivers equipped with highly precise cesium oscillators.
Meteorological data is also collected for accurate evaluation of tropospheric delay (explained later in Lecture 10).
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13. Control Segment II
One MCS, takes data from other 5 tracking stations and consequently predicts satellites orbits by extrapolation.
Computes clock correction for satellite time referred to GPS time frame.
Satellite time synchronization is carried out by connecting MCS to US Naval Observatory (USNO) in Washington DC.
The clock correction data is then sent to transmitting station for uploading.
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14. Control Segment III
Three transmitting stations are involved for transmitting recent data (including broadcast message) to satellites.
These stations also send telemetry commands for repositioning, switching spare components etc.
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15. User Segment
Consists of GPS receiver units with capability to obtain real time positioning.
GPS receivers are hand-held radio-receivers/computers which measure the
time that the radio signal takes to travel from a GPS satellite until it arrives at the GPS antenna.
Using the travel time multiplied by the speed of light provides a calculation of range
to each satellite in view. From this and additional information on the satellites orbit and velocity,
the internal GPS receiver software calculates its position through a process of resection. 
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21. Advantages of GPS
Unlike conventional surveying procedures, there is no need for intervisibility between stations.
Independent of weather conditions as a result of using radio frequencies to transmit the signals.
Use of same field and data reduction procedures results in position accuracy which
independent of network
shape or geometry and are primarily a function of inter-station distance.
GPS surveying provides generally homogeneous accuracy. Hence,
geodetic network planning in the classical sense is
longer relevant. The points can be established wherever they are required
need not be located at evenly distributed sites
atop mountains to satisfy intervisibility, or network geometry criteria.
GPS surveying is more efficient, more flexible and less time consuming positioning
technique than using conventional terrestrial survey technologies.
GPS can be used to obtain high accuracy three dimensional (3D) information, anywhere and
time with relatively little effort on a global datum .
The GPS instrumentation and the data processing software do not radically
even if very high or moderately high accuracies are required (from 1 part in 104 to 1 part in 106 ).
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22. Applications Natural resources Precision farming
Civil Engineering applications
Structural deformations
Open pit mining
Land and marine seismic surveying
Airborne mapping
Seafloor mapping
Vehicle navigation
Transit system
Retail industry
Cadastral surveying
Stakeout (waypoint navigation)
Location based services (LBS)
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29. GPS Observativations Carrier phases Differential GPS
Relative positioning
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30. Sources of Error in GPS Surveying Clock error Atmospheric inferences
Multipath
Satellites configuration
Instrument setup
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31. GPS Surveying Techniques Static FastStatic Post-processed Kinematic
RTK
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32. Data transfer between controller and office computer
Post Processing
Data transfer between controller and office computer
Using office software to process and adjust data
Import and export data and graphs to CAD and GIS programs
Generate drawings and reports
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33. Use of CORS in GPS Surveying
The Continuously Operating Reference Stations (CORS)
The Network
CORS Data File
Use of CORS in GPS Surveying
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34. Setting auto time features Viewing satellite graphs Editing a session
Defining and viewing curtains
Designing a network
Static surveying
FastStatic surveying
Post-processed Kinematic surveying
Setting up and configuring the radio for RTK
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35. Real-Time Kinemeatic (RTK) surveying Performing site calibration
Staking out a point
Performing GPS survey with CORS
Data transfer
Creating and configuring a processing style
Processing baseline
Performing network adjustment
Importing and exporting to CAD and GIS software
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36. Describe the principles of GPS surveying.
Learning outcomes:
Describe the principles of GPS surveying.
Perform planning and network design.
Setup a GPS system for surveying.
Perform Post-processed and RTK surveys and acquire appropriate GPS data.
Perform data transfer.
Post process the GPS data.
Perform error analysis of the acquired GPS and other measured data.
Generate field notes appropriate to GPS surveying.
Produce written reports to communicate results of field surveys.
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37. Review the history of GPS surveying.
Assignments
Review the history of GPS surveying.
Explain the advantages of GPS surveying.
Estimate the accuracy of GPS surveying.
Study the three segments of the GPS surveying.
Differentiate the types of receivers.
Determine the coordinates of a point in space when the distance between the point and a known point is given.
Determine distance with code-ranging method.
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38. Determine distance with carrier-phase method.
Assignments
Determine distance with carrier-phase method.
Explain how the integer of ambiguity is resolved in carrier-phase measurement.
Explain relative positioning and differential GPS.
Study the sources of errors in GPS surveying.
Explain Static, FastStatic, Post-processed Kinematic and RTK surveys, their accuracies and applications.
Design networks.
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39. Chris Rizos, Principles and Practice of GPS Surveying, UNSW 1997
Textbooks
Chris Rizos, Principles and Practice of GPS Surveying, UNSW 1997
Paul Wolf, Elementary Surveying, Prentice Hall, 2002
Alfred Leick, GPS Satellite Surveying, 2nd ed., Wiley, 1995
Simon McElroy, Getting Started with GPS Surveying, GPSCO, 1996
Abdie Tabrizi, Lecture notes, 2004
Trimble Training Manuals, 2005
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