Mr.Samniang Suttara B.Eng. (Civil), M.Eng. (Survey) Topcon Instruments (Thailand) Co.,Ltd. Tel Satellite Surveying

Global Navigation Satellite System What is GNSS ? ADVANTAGE - 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: Satellite Constellation Launched: 1982 Current Satellite Constellation: 18 Planned Constellation: 24 USA Russia E.U. Test Satellite Launched: Dec Current Satellite Constellation: 2 Planned Constellation: 30 Satellites Constellation Technology

COMPASS

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 Satellite Per Launch 3 1 Orbital Planes 3 6 Orbit Inclination Orbit Altitude km km Orbital Period 11 h 15 min 11 h 58 min Ephemerides Pos/Vel/Acc Keplerian Reference Ellipsoid PZ90 WGS84 Carrier Freq. L MHz MHz Carrier Freq. L – MHz MHz C/A-code(L1) MHz MHz P-code(L1,L2) MHZ MHz GLONASSGPS

24 Satellites, 3 active spares 6 Orbital planes inclined at 55 degrees 1 orbit = 11 hours 58 min. 20,200 kilometers height The Space Segment The GPS Space Segment 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 receivedGPSGLONASSGALILEO

Increasing satellites of number GPS GLONASS GALILEO

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 Segment Space Segment User Segment Bi-directional Information Information in one direction System Overview

KWAJALEIN DIEGO GARCIA ASCENSION HAWAII COLORADO SPRINGS (MCS) Control Stations

The User Segment

Receiver Types 1. Navigation receiver Distance measured with C/A code

Receiver Types 2. Geodetic or Surveying receiver

Absolute Positioning (Point Positioning) Relative Positioning (Baselines-Vector) SOLUTION: DX, DY, DZ SOLUTION: X,Y,Z Positioning

How Does GPS Work? GPS Receiver calculates position by one of the following methods: a) Pseudo-Range Measurements Less Accuracy

With codes -C/A code (300 m.) -P code (30 m.) Distance are measured in GPS Positioning

a) Pseudo-Range Measurements Receiver Range Range = ( Time Taken for signal to reach Receiver from Satellite) x (Speed of light = 3*10 8 m/s)

How Does GPS Work? GPS Receiver calculates position by one of the following methods: b) Carrier-Phase Measurements More Accuracy

By signal carriers phase -L1 carriers (19 cm.) -L2 carriers (24 cm.) Distance are measured in GPS Positioning

b) Carrier-Phase Measurements Receiver Range 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 for Deflection 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. Ellipsoid Geometric 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 Geometry Dilution Of Precision (DOP) DOP = σ / σ 0 σ = positioning accuracy σ 0 = observation(pseudorange) accuracy

Good Geometry

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