Introduction to GNSS Base-Station
Dinesh ManandharCenter for Spatial Information ScienceThe University of Tokyo
Contact Information: dinesh@csis.u-tokyo.ac.jp
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 1

GNSS Errors Introduction• GPS or GNSS observation has many types of errors. Due tothese errors, the accuracy of a GPS receiver is limited.
Currently about 10m accuracy is possible with Single
Standard Observation.
• However, some of these errors can be removed or reduced byusing proper observation techniques to provide few
centimeter accuracy. This can be done by using a BaseStation within a limited base-length from the Rover (user)
receiver.
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

2

Slide : 2

How accurate is GPS Position?

50 cm grid

50 cm grid

5 cm grid

SPP (Single Point Position)

DGPS (Differential GPS)RTK (Real Time Kinematic)

How to get accuracy from Red Dots to Green Dots?
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 3

Errors in GPS Observation (L1C/A Signal)
Error Sources
Satellite Orbit
Satellite Clock
Ionosphere Error
Troposphere Error

One-Sigma Error , mTotal
DGPS
2.1
2.1
4.0
0.7

0.0
0.0
0.4
0.2CommentsCommon errors are
removedCommon errors are
reducedMultipath
1.4
1.4
Receiver Circuits
0.5
0.5
If we can remove common errors, position accuracy can be increased.
Common errors are: Satellite Orbit Errors, Clock Errors and Atmospheric Errors (within few km)
Table Source : http://www.edu-observatory.org/gps/gps_accuracy.html#Multipath

The values shown here are only approximate values for comparison purpose. Actual values may differ.
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 4

High-Accuracy Observation Methods• Basically three types of Observation• DGPS (Differential GPS)• Code-phase observation• Requires Base-station (Reference Station)• RTK (Real Time Kinematic)• Code-phase and Carrier-Phase Observation• Requires Base-station (Reference Station)• PPP (Precise Point Positioning)• Code-phase and Carrier-phase observation• Does not require base-station

Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 5

Principle of Differential Correction (DGPS and RTK)30

Send Correction Data to Rover (dX, dY, dZ)
For Real-Time Position

Rover
For RTK, both rover and base receivers
need to use the same satellites
Antenna is installed at aUser in the Field
known-position (x0, y0, z0)(Either fixed or moving)Base-Station

Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 6

SPS (Standard Positioning Service) vs. PPP (Precise Point Positioning)
SPS

PPP

Use Broadcasted orbit andClock Information fromNavigation Data

Use Precise Orbit and Clock Information
Provided by Service Providers

Satellite Tracking Information
Pseudorange, Carrier Phase etc

Satellite Tracking
Information
Pseudorange etc

Additional Error Modelling
Atmospheric Models etc
Meter Level Position
Estimates
Deci-meter to centimeterlevel Position Estimates* This slide is based on Dr. Choy’s lecture note on PPP
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 7

PPP Observation
QZSSGPSCorrection Data
Precise Orbit Data
Precise Clock Error Data
Error Models for Atmospheric Corrections
Ionospheric Correction, TroposphericCorrection, Other Error Models
These correction data are provided by PPP
service providers.

Rover

Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 8

Principle of QZSS MADOCA and CLAS Services
QZSS

GPS

Correction Data:
Satellite Orbit Error of GPS and Other Satellites
Satellite Clock Error of GPS and Other Satellites
Correction data for other satellites
will also be provided
Rover

QZSS provides unique feature of PPP from thesatellite itself by using L6 signal.
There are two services: MADOCA and CLAS
If a GNSS receiver is capable of receiving QZSS L6
signal then high-accuracy (few cm level) positioning
is possible without using base-station data.

Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 9

PPP Online Service Providers
1. CSRS-PPP: Canadian Spatial Reference System, NaturalResources Canada
2. MagicGNSS: GMV
3. CenterPoint RTX: Trimble Navigation
4. GAPS: University of New Brunswick
5. APPS: Jet Propulsion Laboratory
6. SCOUT: Scripps Orbit and Permanent Array Center (SOPAC),
University of California, San Diego
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 10

Submit RINEX Files• CSRS-PPP• https://webapp.geod.nrcan.gc.ca/geod/tools-outils/ppp.php• MagicGNSS• https://magicgnss.gmv.com• CenterPoint RTX• http://trimblertx.com• AUSPOS• http://www.ga.gov.au/bin/gps.pl• GAPS

• http://gaps.gge.unb.ca/submitbasic.php• Trimble RTX• https://trimblertx.com/
Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

Slide : 11

Which Method: DGPS, SBAS, RTK, PPP?

http://www.novatel.com/an-introduction-to-gnss/chapter-5-resolving-errors/

Training on GNSS – Course (T151-40), Organized by: GIC/AIT, CSIS/UT and ICG, held at: GIC/AIT, Thailand from 6 – 10 JAN 2020
Dinesh Manandhar, CSIS, The University of Tokyo, dinesh@csis.u-tokyo.ac.jp

12Slide : 12