GNSS Flashcards
What is GNSS and what does it encompass?
Global Navigation Satelite System:
GPS - US Based
Galileo - EU
BeiDou - China
A GPS position is based on:
Measuring the time and distance from the satellites to the receiver to establish a position
How many satelites are needed to get a two dimensional position (like lat and long)?
- You need 4 satellites for a 3D (lat, long, altitude) position
Why do you need 3 satellites to get a 2D position?
Trillateration
What advantages does GPS have over ADF or VOR?
- Point to Point navigation
- Unlimited range
- Not affected by weather
- Very accurate (to as little as 1 meter)
- Very cheap
What are the pitfalls of GPS?
A user-made waypoint could have been entered incorrectly, leading you to the wrong place
When was GPS originally designed?
In the US by the Department of Defence
GNSS horizontal and verticle positions are accurate to:
6 and 8 meters respectively 95% of the time
What two frequencies does the GNSS system transmit on continuously?
1227.6 and 1575.42 Mhz
GPS is line of sight, what problems can that create?
Signal masking/blocking can be an issue.
This can occure when there is mountainous terrain, man-made structures, or a poorly located antenna on the AC.
Still tho GSP coverage is way better than anythign else we have
How many atomic clocks are on board each satallite?
4, with a guaranteed accuracy down to 1 nanosecond (1 billionth of a second)
GPS accuracy is dependent on the relative position (the geometry) of the _____
Satellite
The further apart the satellites are from one another, the more accurate your position will be
What is differential GPS?
A GPS that uses differential techniques to achieve better accuracy.
This is done by locating a receiver on the ground at a precisely surveyed position
What are the two types of differential GPSs?
WAAS - Wide Area Augmentation System
LAAS - Local Area Augmentation System
What is LAAS?
An all-weather aircraft landing system based on real-time differential correction of the GPS signal
We dont have it in Canada
Basic GPS terms
