24 Questions
What can cause signal reception blockage and position errors in GPS?
Buildings, terrain, electronic interference, or dense foliage
What is the ideal satellite geometry in GPS?
Satellites are located at wide angles relative to each other
What is the purpose of the Control Segment in GPS?
To monitor and control satellites
What is the altitude of GPS satellites in their circular orbits?
20,200 km
How do GPS satellites orient themselves?
Towards the sun and the Earth
What is the purpose of the User Segment in GPS?
To receive and process GPS signals
What is the process used by GPS to determine user position?
3-dimensional Trilateration
How many GPS satellites are required to be in line of sight for accurate positioning?
At least 6
What is the primary reason for the delay in reception of the code emitted by the Satellite?
The distance the wave has to travel from the Satellite to the Earth
What is the purpose of the fourth signal received from the fourth Satellite?
To determine the exact location of the GPS receiver
What is the equation used to calculate the distance between the Satellite and the receiver?
d = vt
What is the speed of radio waves, which is used in the calculation of distance?
300 000 km/s
What is the role of the atomic clock in the GPS receiver?
To calculate the delay in reception of the code
How many signals are required to determine the exact location of the GPS receiver?
Four
What is the primary function of the GPS receiver?
To receive and calculate the distance from the Satellite
What is the result of the calculation of the delay in reception of the code?
The distance from the Satellite
What is the altitude of the GPS satellites' circular orbits?
20,200 km
What is the purpose of the Control Segment in GPS?
To monitor and control GPS satellites
What is the minimum number of GPS satellites required to be within line of sight from any location on the planet?
Six
How do GPS satellites maintain their orientation in space?
By continuously orienting themselves towards the sun and earth
What is the primary function of the User Segment in GPS?
To receive and process GPS signals from satellites
What is the mathematical principle behind GPS?
Trilateration
What is the prerequisite mathematical concept for understanding 3-dimensional Trilateration?
2-D Trilateration
What is the period of the GPS satellites' orbits?
12 hours
Study Notes
GPS Limitations
- Buildings, terrain, electronic interference, and dense foliage can block signal reception and cause position errors or no position reading.
- GPS units typically do not work indoors, underwater, or underground.
- Satellite geometry/shading affects signal reception, with ideal geometry occurring when satellites are at wide angles relative to each other.
GNSS and GPS Components
- Global Navigation Satellite System (GNSS) is the standard generic term for navigation satellite systems like GPS, GLONASS, GALILEO, BeiDou, QZSS, and NAVIC.
- There are two types of GNSS constellations: Global and Regional.
- GPS consists of three parts: Space Segment, Control Segment, and User Segment.
GPS Space Segment
- GPS satellites fly in circular orbits at an altitude of 20,200 km and with a period of 12 hours.
- They are powered by solar cells and continuously orient themselves to point their solar panels towards the sun and their antenna towards the earth.
- Orbits are designed to ensure at least six satellites are always within line of sight from any location on the planet.
GPS Control Segment
- Control Segments monitor and control satellites.
- Ground stations identify their location, consisting of a Master Control System, Monitor Stations, and Ground Antennas.
GPS User Segment
- Receivers are constantly listening for signals from the satellites.
- Highly advanced receivers can identify the exact location within a fraction of an inch.
How GPS Works
- GPS works based on a simple mathematical process called 3-dimensional Trilateration.
- 3-dimensional Trilateration involves using four satellite signals to determine the exact location of the GPS receiver.
- The distance is calculated using the equation: d = vt, where d is the distance, v is the speed of light, and t is the time.
Radio Waves
- Radio waves are low-energy electromagnetic waves used for long-distance communication.
- They travel at the speed of light (300,000 km/s).
- The distance calculation uses the equation: d = vt, where the delay in receiving the signal is used to find the time (t) and subsequently the distance (d).
3-Dimensional Trilateration
- 3-dimensional Trilateration involves using four satellite signals to determine the exact location of the GPS receiver.
- It requires a basic knowledge of 2-D Trilateration, which involves using circles to locate an object.
- 2-D Trilateration involves using multiple circles to narrow down the possible location of an object.
This quiz covers the factors that can affect GPS signal reception, including physical barriers, satellite geometry, and environmental conditions. It also explores the limitations of GPS units in various environments.
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