ET VOL 5 Ch 1 Flashcards Preview

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Flashcards in ET VOL 5 Ch 1 Deck (62):
1

2

Tactical navigation is directly concerned with maneuvering the ship in navigable waters.

false

3

Estimating ship’s position between known navigational points or fixes is known as

dead reckoning

4

Radio navigation consists of which of the following categories?

1. Sub-space systems (SATNAV, TRANSIT, NAVSTAR) 2. Space–based systems (omega, loran)

5

One of the characteristics of dead reckoning is that the accuracy of the estimated position never exceeds the navigation method used to obtain the last fix. What happens to the accuracy of the estimated position over time?

It fluctuates

6

Referring to landmarks with known positions on earth describes which one of the following navigation methods?

piloting

7

Which of the following actions required to determine position in piloting is/are not required in electronic navigation?

Seeing the landmarks

8

According to the 1992 Federal Radio Navigation Plan, which of the following systems will become the primary reference navigation system for surface ships?

NAVSTAR(GPS)

9

what is LORAN

Long Range Aid to NAvigation

10

What is omega

VLF radio NAvigation

11

LORAN takes advantage of what radio signal characteristic?

Constant velocity

12

OMEGA is a hyperbolic phase— difference measuring system that compares the phase angle of two or more radio signals synchronized to what device or factor?

A common time base

13

Which navigation system continually computes the latitude and longitude of a ship by sensing acceleration?

SINS (Ships inertial navigation system)

14

A ship’s inertial navigation system is dependent on celestial, sight, and radio navigation aids.

false

15

What device measures changes in speed or direction along the axis in which it lies?

Accelerometer

16

What type of system is used to keep a SINS platform stabilized?

Gyro

17

Which of the following is a standalone SINS?

AN/WSN-5

18

Approximately how often can operators using the NNSS obtain fixes?

Every 2 hours

19

NNSS satellites transmit phase modulated data every 2 minutes on how many rf carriers?

2

20

What are the two types of NNSS satellite parameters included in the phase-modulated data?

Fixed and variable

21

The nominal orbit of NNSS satellites is what type of orbital parameter?

fixed

22

NNSS satellite data can be used as an accurate time reference.

true

23

NNSS satellite refined orbits are calculated at which of the following facilities?

Tracking station

24

Which of the following facilities calculates NNSS satellite clock error before satellite message injection?

Control center

25

Approximately how long does it take the injection station to transmit information to an NNSS satellite?

15 seconds

26

If errors are detected during a readback of freshly injected satellite data, how often is NNSS satellite message injection repeated until the transmission is verified as being correct?

every 2 minutes

27

At what point during the satellite pass will expansion effects cause the received frequencies to drop below the generated frequencies?

T3- Leaving away from

28

At what point will the received frequencies exactly match the transmitted frequencies?

T2-EVEN

29

At what point will compression effects cause the received frequencies to be higher than the transmitted frequencies?

T1- Approaching Fast

30

Which of the following factors affects the measurement of Doppler shift?

Refraction

31

Satellites broadcast at what to freqs to fix refraction?

150 and 400 MHZ

32

To solve the problem of Doppler shift accuracy, satellites are designed to transmit on how many frequencies?

2

33

Accurate NNSS position fixes for a moving vessel require what additional computation?

vessels speed

34

Which ship’s system will provide the information required to perform the additional computation required by NNSS?

SINS

35

Given the orbital parameters of a satellite, the Doppler shift of the signal transmitted from that satellite, and the velocity of a vessel, it is possible to obtain a navigational fix if the satellite is within what distance from the navigation set?

LOS Line-of-Sight

36

One of the capabilities of the AN/WRN-5 includes time-ordered alerts for up to how many satellites?

8

37

What is the “at sea” accuracy of the AN/SRN-19(V)2?

.25 miles

38

What activity may degrade the accuracy of the AN/SRN-19(V)2?

sunspots

39

You are initializing the AN/SRN– 19(V)2. In addition to programing the set’s position, what other parameter must you enter?

antenna length

40

What navigational system will replace the NNSS?

NAVSTAR GPS

41

Which of the following terms describe GPS satellite positioning data?

Almanac (data for ground satellites) and ephemeris (position data for single satellite)

42

How often is the GPS satellite navigation data message updated?

every 24 hours

43

What facility transmits the data required to update the GPS satellite navigation data message?

Manned Control Center

44

There are how many (a) active spare and (b) active operational GPS satellites?

(a) 21 (b) 3

45

How many earth orbits will each GPS satellite complete in a 24–hour period

2

46

What communications technique is used for GPS satellite broadcasts?

Spread–spectrum

47

What are the to Spread-Spectrum Rf Freqs?

1575.42 MHz (L1-RF) 1227.60 MHz (L2-RF)

48

GPS satellites are positioned so a minimum of how many satellites are observable to a user anywhere on earth?

4

49

Which of the two codes (C/A and P) transmitted by GPS satellites is NOT available to civilian users?

Precise code (only Military)

50

Which of the following data is NOT included in the GPS NAV–msg?

Spectral

51

GPS navigation is based on what principle?

Satellite ranging (measure time from Satellite to NAVSET divide travel time by speed of light

52

Within how many feet can GPS determine position fixes?

50ft

53

To obtain the above accuracy, how many satellite inputs are required

4

54

How is the time difference between satellite transmission and when the navigation set receives this signal related to the distance between the satellite and the receiver?

Directly proportional

55

GPS satellites use atomic clocks; the receivers do not. What type of error must be computed based on this fact?

Clock

56

Tropospheric delay is predicted and included in what satellite data?

Almanac

57

Ionospheric delay is greatest when a signal is received from directly overhead.

false (near the horizon)

58

Of the frequencies listed below, which one will ionospheric delay phase–shift the most?

1227.60 MHz L2

59

Satellite signals reflecting off one or more objects before reaching the navigation set produce what type of reception?

Multipath-reached it different times

60

What data do operators enter into the AN/WRN-6(V) to speed up satellite acquisition?

Time and date Current position

61

Which of the following is the normal operating mode of the AN/WRN-6(V)?

Navigation

62

Which of the following is a portable GPS receiver?

AN/PSN–8