Transcript TopNet Topcon’s Suite of Reference Station and Network RTK

Satellite Surveying
Mr.Samniang Suttara
B.Eng. (Civil), M.Eng. (Survey)
Topcon Instruments (Thailand) Co.,Ltd.
E-Mail : [email protected]
Tel. 08-1821-1297
What is GNSS ?
Global Navigation Satellite System
ADVANTAGE
- Accuracy from meter to millimeter
- Everywhere
- Everytime
- One system coordination
- Many user segment
- No expenses
GNSS Provider?
• 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.
Constellation Technology
USA
• Launched: 1978
• 24 Satellite Constellation
Russia
• Launched: 1982
• Current Satellite Constellation: 18
• Planned Constellation: 24
.
E.U
• Test Satellite Launched: Dec. 2005
• Current Satellite Constellation: 2
• Planned Constellation: 30 Satellites
Constellation Technology
COMPASS
Satellites
1.
GPS Satellites
2. GLONASS Satellites
Satellites
3. GALILEO Satellites
4. COMPASS Satellites
Number of Satellites
Launch Vehicle
GLONASS
GPS
24 (24)
24 (27)
Proton k/DM-2
Delta 2-7925
Satellite Per Launch
3
1
Orbital Planes
3
6
Orbit Inclination
Orbit Altitude
Orbital Period
Ephemerides
Reference Ellipsoid
64.8
55
19100 km
20200 km
11 h 15 min
11 h 58 min
Pos/Vel/Acc
Keplerian
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
The GPS Space Segment
•
24 Satellites, 3 active spares
•
6 Orbital planes inclined at 55 degrees
•
1 orbit = 11 hours 58 min.
•
20,200 kilometers height
The GLONASS Space Segment
• 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
GALILEO
GLONASS
GPS
Increasing satellites of number
GALILEO
GLONASS
GPS
GPS Components
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.
System Overview
Space Segment
Information in
one direction
User Segment
Bi-directional
Information
Control Segment
Control Stations
COLORADO
SPRINGS
(MCS)
HAWAII
KWAJALEIN
ASCENSION
DIEGO
GARCIA
The User Segment
The User Segment
The User Segment
Receiver Types
1. Navigation receiver
Distance measured with C/A code
Receiver Types
2. Geodetic or Surveying receiver
Positioning
Absolute Positioning (Point Positioning)
SOLUTION: X,Y,Z
Relative Positioning (Baselines-Vector)
SOLUTION: DX, DY, DZ
How Does GPS Work?
GPS Receiver calculates position by one of
the following methods:
a) Pseudo-Range Measurements
Less Accuracy
Distance are measured in
GPS Positioning
With codes
-C/A code (300 m.)
-P code (30 m.)
a) Pseudo-Range Measurements
Range = (Time Taken for signal to reach Receiver from Satellite)
x (Speed of light = 3*108 m/s)
Receiver
How Does GPS Work?
GPS Receiver calculates position by one of
the following methods:
b) Carrier-Phase Measurements
More Accuracy
Distance are measured in
GPS Positioning
By signal carriers phase
-L1 carriers (19 cm.)
-L2 carriers (24 cm.)
b) Carrier-Phase Measurements
Range = (Whole no. of Wavelengths from Satellite to Receiver)
+ (Fractional Part of Wavelength)
Receiver
Errors in GPS Survey
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.
Earth History
After that...a Geoid (Helmert, 1884)
Geoid
Ellipsoid
Helmert Geoid model accounts for
Deflection of the vertical
Earth Surface Representation
TERRAIN
GEOID (MSL)
Geoid
• Ocean surface free of disturbances (Helmert, 1884).
• Equipotential Surface of the Earth’s Gravity Field.
Ellipsoid
Geometric representation of the Earth Surface.
ELLIPSOID
Heights
H
TERRAIN
h
N
GEOID (MSL)
ELLIPSOID
N=h-H
h= Ellipsoidal height
H= Orthometric height
N = Geoid Undulation
How EGM works ?
-EGM96
-EGM2008
Orthometric Heights
Coordinate System
Z
ECEF Coordinate System (X,Y,Z)
Topocentric System
(N,E,U)
Geographic Coordinates (b,l,h)
Normal to
Ellipsoid
(CIO)
Up
North
East
Station
j
l
X
(Greenwich Meridian)
Y
Field Methods Survey
• Static Survey
• Fast or Rapid Static Survey
• Kinematic Survey
• Real Time Kinematic (RTK) Survey
- Single base
- Network RTK (VRS, MAC, FKP)
Mission Planning
GPS & GLONASS
GPS Only
Dilution of Precision (DOP)
• 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
(Geometrical)
Dilution Of Precision (DOP)
DOP = σ /σ0
Poor Geometry
σ = positioning accuracy
σ0 = observation(pseudorange)
accuracy
Good Geometry
Static Survey
Static GPS+ Survey
Process data
Fast Static
The RTK Concept
RTCM vs. CMR
• Radio Technical Commission for Maritime
Services (More than twice as long of a message
format)
• Compact Measurement Record
VRS Network
VRS Network
VRS Network