GPS

Question 1

GPS stands for

Answer 1

global positioning system

Question 2

GPS

Answer 2

technology that broadcasts satellite signals for navigation and position determination on earth

Question 3

examples of how are GPS receivers used

Answer 3

1. in car navigation
2. cell phones
3. smart watches

Question 4

is GPS free

Answer 4

yes

Question 5

when and what was the first use of GPS

Answer 5

1964 with the NAVSAT system

Question 6

what was NAVSAT used for

Answer 6

tracking the locations of commercial and military sea vessels

Question 7

what was the origin of the GPS we use

Answer 7

the NAVSTAR system developed by USA

Question 8

what was the first use of GPS outside of the USA

Answer 8

Soviet Union shoots down Korean Airline in 1983

Question 9

what administration allowed worldwide access to the GPS

Answer 9

Reagan administration

Question 10

GNSS

Answer 10

the overall term for technology that uses signals to find locations on Earth

Question 11

what does GNSS stand for

Answer 11

global navigation satellite system

Question 12

what are the three segments of GPS

Answer 12

1. space segment
2. control segment
3. user segment

Question 13

what segment(s) does the space segment send data to

Answer 13

control and user segment

Question 14

how many satellites does GPS require

Answer 14

24

Question 14

how many orbital planes are there for the satellites for GPS

Answer 14

six orbital planes

Question 14

what is the orbit altitude of the satellites for GPS

Answer 14

20 200 km

Question 15

how many degrees are the six orbital planes for the GPS satellites separated

Answer 15

60 degrees

Question 16

how many satellites are visible from any point on earth

Answer 16

5 to 8

Question 17

describe the data from the space segment of GPS

Answer 17

ephemeris

Question 18

ephemeris data

Answer 18

information about the satellite’s status, orbit and precise location

Question 19

what type of GPS data is sent to users from a satellite

Answer 19

ephemeris data

Question 20

how is the data from the satellite sent to the control stations and users

Answer 20

done through digital pseudo-random codes

Question 21

C/A code in satellite data

Answer 21

information accessible by ALL GPS Receivers

Question 22

what is a frequency in C/A codes

Answer 22

L1 - navigation information (time and position)

Question 23

what are P-codes

Answer 23

information from satellites that is accessible by MILITARY receivers

Question 24

what L level data is received by P-code data

Answer 24

L1 and L2

Question 25

what does L2 measure

Answer 25

atmospheric interference

Question 26

Y -codes

Answer 26

encrypted version of P-code intended for MILITARY use

Question 27

what is the control segment of GPS

Answer 27

series of worldwide ground stations that monitor signals from GPS satellites

Question 28

where is the master control center for GPS satellites

Answer 28

Colorado

Question 29

what type of corrections are sent from the control station to a GPS satellite

Answer 29

1. orbit correction 2. time corrections 3. atmospheric condition corrections

Question 30

what is the user segment of GPS

Answer 30

GPS receivers on the ground that pick up satellite signals

Question 31

what controls the number of satellites a GPS receiver will connect to

Answer 31

the number of channels (12 channels = 12 satellites)

Question 32

what are single frequency GPS receivers

Answer 32

receivers that only use the L1 frequency

Question 33

what type of data do single frequency GPS receivers have access to

Answer 33

time and position of satellite

Question 34

what type of data do dual frequency GPS receivers have access to

Answer 34

L1 and L2 (military recievers)

Question 35

what are dual frequency GPS receivers

Answer 35

receivers that use L1 and L2

Question 36

what is needed with GPS receivers for accurate readings

Answer 36

direct line of sight of the satellite

Question 37

what is trilateration

Answer 37

a method to find your position based on the distance from at least THREE known points

Question 38

how does 3D trilateration differ from regular trilateration

Answer 38

finding your position on earth's surface, which is not flat but an ellipsoid

Question 39

what speed does the signal from the satellite travel at

Answer 39

speed of light

Question 40

what is pseudo-range

Answer 40

the distance between a GPS satellite and a GPS receiver

Question 41

how to calculate pseudo-range

Answer 41

speed of light * transmission time

Question 42

where is your location if two satellites are used

Answer 42

the location is somewhere along the boundary

Question 43

what happens when trilateration is done with 3 instead of 2 satellites

Answer 43

the location narrows to two points

Question 44

of the two points found with three satellites in trilateration, where are they

Answer 44

one is in space and the other is on earth

Question 45

what causes trilateration to NOT be accurate

Answer 45

time the signal takes to reach the receiver (if time is a little off from speed of light = huge distance on earth that's off)

Question 46

what type of clocks do satellites use to reduce time errors

Answer 46

atomic clocks

Question 47

what type of clocks do receivers use to reduce time errors

Answer 47

quartz clock

Question 48

what is used in trilateration to account for time errors

Answer 48

a fourth satellite

Question 49

what are 5 sources of errors in GPS

Answer 49

1. time dilution of precision 2. position dilution of precision 3. atmospheric interference 4. multipath signals 5. selective availability

Question 50

what is position dilution of precision

Answer 50

error introduced due to geometric position of satellite

Question 51

what results in higher position accuracy

Answer 51

a wider distribution of satellites

Question 52

where are two instances of atmospheric interference

Answer 52

1. ionosphere (density and stratification variation) 2. troposphere (atmosphere pressure and moisture)

Question 53

does the ionosphere cause larger error or the troposphere

Answer 53

ionosphere

Question 54

what is multipath signal error

Answer 54

an error caused by the reflection of GPS signals from surrounding surfaces

Question 55

what can be used to have the clearest signal to the satellite

Answer 55

antennas that raise the receiver so it has access to clear sky

Question 56

what is differential GPS

Answer 56

a method of using ground based corrections in addition to satellite signals

Question 57

where are base stations placed in DGPS

Answer 57

locations with known coordinates

Question 58

how do base stations work best

Answer 58

when built close to receivers

Question 59

what is real time kinematics

Answer 59

combination of GPS signals and a base station to provide real time corrections

Question 60

what is post processed kinematics

Answer 60

combination of GPS signals and a base station to correct location information POST data collection

Question 61

what is WAAS

Answer 61

a network of ground stations that measure variation in GPS signal

Question 62

importance of WAAS

Answer 62

reduces the error to 3 meters or less