GNSS

1. Introduction to GNSS
GI 7692 Total Station and GPS Surveying
Unit I (Part)

2. Satellite Navigation
A satellite navigation is a system that uses satellites to provide
autonomous geo-spatial positioning. It allows small electronic receivers to
determine their location (longitude, latitude, and altitude/elevation) to high
precision (within a few centimeters to metres) using time signals transmitted
along a line of sight by microwave from satellites.
The system can be used for providing position, navigation or for tracking
the position of something fitted with a receiver (satellite tracking). The signals
also allow the electronic receiver to calculate the current local time to high
precision, which allows time synchronization. These uses are collectively known
as Positioning, Navigation and Timing (PNT).

4. Satellite Navigation
Positioning, the ability to accurately and precisely determine one's location
and orientation two-dimensionally (or three-dimensionally when required)
referenced to a standard geodetic system (such as World Geodetic System
1984, or WGS84);
Navigation, the ability to determine current and desired position (relative or
absolute) and apply corrections to course, orientation, and speed to attain a
desired position anywhere around the world, from sub-surface to surface and
from surface to space; and
Timing, the ability to acquire and maintain accurate and precise time from a
standard (Coordinated Universal Time, or UTC), anywhere in the world and
within user-defined timeliness parameters. Timing also includes time transfer.

12. GEO – Geosynchronous Equatorial Orbit
MEO – Medium Earth Orbit
HEO – Highly elliptical orbit
IGSO – Inclined geosynchronous orbit

18. The basic principle of operation on which GNSS
systems is based is often referred to as resection
(also called triangulation), and it involves estimating
the distances from at least three satellites orbiting
the Earth along different and sufficiently separated
trajectories to determine the position of an object in
2-D along with the uncertainty in measurement. If
four or more satellites are in view, the receiver can
determine three-dimensional (3D) position (latitude,
longitude, and altitude) of the user. GPS is one-way
ranging or pseudo ranging.