Download - Mr.Samniang Suttara B.Eng. (Civil), M.Eng. (Survey) Topcon Instruments (Thailand) Co.,Ltd
Mr.Samniang SuttaraB.Eng. (Civil), M.Eng. (Survey)
Topcon Instruments (Thailand) Co.,Ltd.
E-Mail : [email protected]
Tel. 08-1821-1297
Satellite Surveying
Global Navigation Satellite System
What is GNSS ?
ADVANTAGEADVANTAGE
- Accuracy from meter to millimeter- Everywhere- Everytime- One system coordination- Many user segment- No expenses
- Accuracy from meter to millimeter- Everywhere- Everytime- One system coordination- Many user segment- No expenses
• NAVSTAR GPS (Global Positioning System) By USA.
• GLONASS (GLObal NAvigation Satellite System or GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) By Russian.
• GALILEO By The European Space Agency (ESA)
• COMPASS By China.
GNSS Provider?
• Launched: 1978• 24 Satellite Constellation
• Launched: 1982• Current Satellite Constellation: 18• Planned Constellation: 24
USA
Russia
E.U.• Test Satellite Launched: Dec. 2005• Current Satellite Constellation: 2• Planned Constellation: 30 Satellites
Constellation TechnologyConstellation Technology
Constellation TechnologyConstellation Technology
COMPASSCOMPASS
1. GPS Satellites
Satellites
2. GLONASS Satellites
Satellites
3. GALILEO Satellites 4. COMPASS Satellites
Number of Satellites 24 (24) 24 (27)
Launch Vehicle Proton k/DM-2 Delta 2-
7925
Satellite Per Launch 3 1
Orbital Planes 3 6
Orbit Inclination 64.8
55
Orbit Altitude 19100 km 20200 km
Orbital Period 11 h 15 min 11 h 58 min
Ephemerides Pos/Vel/Acc Keplerian
Reference Ellipsoid PZ90 WGS84
Carrier Freq. L1 1602.5625 - 1615.5 MHz
1575.42 MHz
Carrier Freq. L2 1246.4375 – 1256.5 MHz
1227.60 MHz
C/A-code(L1) 0.511 MHz 1.023
MHz
P-code(L1,L2) 5.110 MHZ 10.23
MHz
GLONASSGLONASS GPS
• 24 Satellites, 3 active spares
• 6 Orbital planes inclined at 55 degrees
• 1 orbit = 11 hours 58 min.
• 20,200 kilometers height
The The GPS Space Segment Space Segment
The GLONASS Space The GLONASS Space SegmentSegment
• 24 Satellites, 3 active spares
• 3 Orbital planes inclined at 64.8
degrees
• 1 orbit = 11 hours 15 min.
• 19,100 kilometers height
GNSS Comparison
All the satellite signals are received
GPSGPSGLONASSGLONASSGALILEOGALILEO
Increasing satellites of number
GPSGPS
GLONASSGLONASS
GALILEOGALILEO
1. Space Segment
Constellations of satellites.
2. Control Segment
Monitor and control stations for tracking and managing satellites.
3. User Segment
Receivers designed to receive, decode and process satellite data.
GPS Components
Control Control SegmentSegment
Space Space SegmentSegment
User User SegmentSegment
Bi-directional Information
Information in one direction
System OverviewSystem Overview
KWAJALEIN
DIEGOGARCIA
ASCENSION
HAWAII
COLORADO SPRINGS (MCS)
Control Stations
The User Segment
The User Segment
The User Segment
Receiver Types
1. Navigation receiverDistance measured with C/A code
Receiver Types
2. Geodetic or Surveying receiver
Absolute Positioning (Point Positioning)Absolute Positioning (Point Positioning)
Relative Positioning (Baselines-Vector)Relative Positioning (Baselines-Vector)
SOLUTION:SOLUTION: DX, DY, DZ DX, DY, DZ
SOLUTION:SOLUTION: X,Y,ZX,Y,Z
Positioning
How Does GPS Work?
GPS Receiver calculates position by one of GPS Receiver calculates position by one of the following methods:the following methods:
a) Pseudo-Range Measurementsa) Pseudo-Range MeasurementsLess AccuracyLess Accuracy
With codesWith codes-C/A code (300 m.)C/A code (300 m.)-P code (30 m.)
Distance are measured in GPS Positioning
a) Pseudo-Range Measurements
Receiver
RangeRange
Range
Ran
ge
Range = (Time Taken for signal to reach Receiver from Satellite) x (Speed of light = 3*108 m/s)
How Does GPS Work?
GPS Receiver calculates position by one of GPS Receiver calculates position by one of the following methods:the following methods:
b) Carrier-Phase Measurementsb) Carrier-Phase MeasurementsMore AccuracyMore Accuracy
By signal carriers phase-L1 carriers (19 cm.)-L2 carriers (24 cm.)
Distance are measured in GPS Positioning
b) Carrier-Phase Measurements
Receiver
RangeRange
Range
Ran
ge
Range = (Whole no. of Wavelengths from Satellite to Receiver) + (Fractional Part of Wavelength)
1. Satellite - Orbit = 5 m.
- Clock = 1 m.
2. Signal Propagation – Ionospheric (Dual freq) = cm.- dm.
- Troposheric = dm.
- Multipath = 5 m.
3. Receiver - Observation noise = 1-10 m.
- Hardware delay = m.
- Antenna phase center = mm.- cm.
Errors in GPS Survey
After that...a Geoid (Helmert, 1884)
Geoid
Ellipsoid
Helmert Geoid model accounts forDeflection of the vertical
Earth History
GEOID (MSL)
ELLIPSOID
TERRAIN
Geoid • Ocean surface free of disturbances (Helmert, 1884).• Equipotential Surface of the Earth’s Gravity Field.
EllipsoidGeometric representation of the Earth Surface.
Earth Surface Representation
GEOID (MSL)
ELLIPSOID
TERRAIN
h= Ellipsoidal height
H= Orthometric height
N = Geoid Undulation
N=h-H
Heights
h N
H
How EGM works ?-EGM96-EGM2008
Orthometric Heights
X (Greenwich Meridian)
Z (CIO)
Normal to Ellipsoid
North
East
Up
Station
Y
ECEF Coordinate System (X,Y,Z)Topocentric System (N,E,U)Geographic Coordinates (b,l,h)
Coordinate System
• Static Survey
• Fast or Rapid Static Survey
• Kinematic Survey
• Real Time Kinematic (RTK) Survey
- Single base
- Network RTK (VRS, MAC, FKP)
Field Methods Survey
GPS Only
GPS & GLONASS
Mission Planning
• VDOP =standard deviation in vertical
• HDOP =standard deviation in horizontal position(2D)
• PDOP =standard deviation in position(3D)
• TDOP =standard deviation in Time
• GDOP =standard deviation in position(3D) and time
Dilution of Precision (DOP)
(Geometrical)
Poor Poor GeometryGeometry
Dilution Of Precision (DOP)
DOP = σ /σ0
σ = positioning accuracy
σ0 = observation(pseudorange) accuracy
Good Good GeometryGeometry
Static Survey
Static GPS+ Survey
Process data
Fast Static
The RTK Concept
• Radio Technical Commission for Maritime Services (More than twice as long of a message format)
• Compact Measurement Record
RTCM vs. CMR
VRS Network
VRS Network
VRS Network