1
GNSS
Global Navigation Satellite
System
Engr. M. Hamza Khalid
Engr. M. Hamza Khalid
GNSS 2
The basic question…
Where am I on Earth?
Engr. M. Hamza Khalid
GNSS 3
Satellite Trilateration
Distance = Speed of light x Time
With minimum 4 satellites,
Engr. M. Hamza Khalid
you can determine your
location on Earth
GNSS 4
GNSS – Global Navigation Satellite System
GNSS stands for Global Navigation Satellite System and is an umbrella term that encompasses all global
satellite positioning systems. This includes constellations of satellites orbiting over the earth’s surface
and continuously transmitting signals that enable users to determine their position.
System Country
GPS USA
BeiDou China
Galileo European Union
GLONASS Russia
IRNSS India
Quasi-Zenith Japan
Engr. M. Hamza Khalid
GNSS 5
GNSS – Uses
1. Location – determining your position in the world
2. Navigation – identifying the best route from one location to another
3. Tracking – monitoring an object’s movement in the world
4. Mapping – creating maps of a specific area
5. Timing – computing precise timing within billionths of a second
Engr. M. Hamza Khalid
GNSS 6
Space Segment
GNSS – Architecture
Satellites
Broadcast Signals
Data Uploading Station Control Station Base Station
Engr. M. Hamza Khalid Control Segment User Segment
GNSS 7
GPS – Techniques
GPS
Autonomous / Standalone Differential GPS
Differential Post Processing / Differential Real Time /
Static Kinematic
Engr. M. Hamza Khalid
GNSS 8
GPS – Techniques
1. Autonomous / Stand Alone
Using a single stand-alone receiver. Used by hikers,
ships that are far out at sea and the military. Position
Accuracy is better than 100m for civilian users and
about 20m for military users.
Engr. M. Hamza Khalid
GNSS 9
GPS – Techniques
2. Differential GPS
Differential correction is a technique that greatly
increases the accuracy of the collected GPS data.
It involves using a receiver at a known location -
the "base station“- and comparing that data with
GPS positions collected from unknown locations
with "roving receivers."
Engr. M. Hamza Khalid
GNSS 10
GPS – Techniques
2. Differential GPS
It is possible to determine the position of Rover ‘B’
in relation to Reference ‘A’ provided
Coordinates of ‘A’ are known
• Differential Positioning eliminates errors in the
sat. and receiver clocks and minimizes
atmospheric delays
• Accuracy 5 mm - 5 m
A BB
Engr. M. Hamza Khalid
?
GNSS 11
GPS – Techniques
2. Differential GPS
Engr. M. Hamza Khalid
GNSS 12
Task
Determine the co-ordinates of the Traverse points using GPS-Post Processing and compare the results with
Traverse Computations.
Engr. M. Hamza Khalid
