Ch 4 Geospatial Flashcards
- What is GPS? What are three essential components/segments in GPS?
A geospatial tech uses signal broadcast from satellites for navigation.
Three components are Space, Control, and User segment
What is a GPS constellation? What is the minimum number of satellites for a full constellation?
A group of satellites working together
Minimum is 24
How many orbit planes are in a GPS constellation? How many satellites are in each orbit?
Six
4 satellites in each orbit
How many orbits around Earth does a GPS satellite make every day? What is the flying altitude of these satellites?
Two orbits
Flying altitude is 20,200 km
What is the use of ground control stations?
Track and monitor signals being transmitted by satellites
What does a “12-channel” GPS receiver mean?
Can pick up signals from up to 12 satellites
What is the difference between a single frequency and dual frequency GPS receiver?
Single Frequency: receiver can only pick up L1 frequency
Dual Frequency: Can pick up L1 and L2
Describe the process of trilateration in determining a location on Earth.
Using three points of reference to determine your location
Which two atmospheric layers can cause a GPS signal delay? Why?
Ionosphere: alter speed of satellite signals
Troposphere: most where occurs /water vapor
Both have internal degradation
What are two popular methods used to improve GPS accuracy? How do they work?
Differential GPS (DGPS): one more base stations at locations on the ground
Continuously Operating Reference Stations (CORS): collects GPS info and makes it available to users of GPA data to make accurate position measurements.
What is a multipath effect? How does it influence GPS accuracy?
Delays into the reception of the signal because the signal is reaching the receiver later than it should
Caused by blocked by buildings/ signal reflected off of buildings
Makes GPS not accurate
What is the minimum number of GPS satellites needed to determine a location?
4 satellites
