Nav. Equipment

Question 1

You must be able to switch to hand steering within how many secs in Areas of high traffic density - Restricted Visibility - When ship manoeuvring is critical “Such as anchoring”

Answer 1

30 seconds

Question 2

What are the 2 autopilot modes?

Answer 2

Research

Question 3

An impeller or paddle wheel will give speed over the ground or through water?

Answer 3

STW

Question 4

Can the doppler log do both STW and SOG?

Answer 4

Yes!

Question 5

Which volume of ALRS is DGPS info found in?

Answer 5

2

Question 6

How often should emergency steering drills be done?

Answer 6

Atleast every 3 months

Question 7

Which logbook must a steering drill be logged in?

Answer 7

OL

Question 8

2 of the most important differences between raster and vector?

Answer 8

Route checking

Setting alarms on safety info

Question 9

GPS provides a global positioning capability giving 95% accuracy in the order of +/- (?) metres according to
MGN 379

Answer 9

25m

Question 10

Where will information on CARRIAGE REQUIREMENTS for a UK ship be found aswell how it is brought into law?

Answer 10

SOLAS CH.5 reg. 19 Carriage Requiresments shipborne nav equipment

Brought into UK law via the MERCHANT SHIPPING (SAFETY OF NAV) REGULATIONS 2020

Guidance for non lawyers in MGN610

Question 11

Give the name of the EU, US, Russian & Chinese GNSS Satellites

Answer 11

EU GALILEO
US NAVSTAR
RUSSIAN GLONASS
CHINESE BeiDei

Question 12

How many GPS satellites ?

Answer 12

24 to ensure multiple are visible at any point / any time on earth.

Question 13

Operation of GPS system:
(5)

Answer 13

Transmitting station (A) emits a signal from a know position

Signal received by Observer station (O)

Speed remains constant = Time gives distance

Thus providing a circle of position

Repeating the process atleast 2 or 3 times (B+C) will provide a fix

Question 14

What is a DOP value?

Answer 14

Dilution of precision

Question 15

HDOP:
Value between 1 to 8.

What distance must the HDOP value be multiplied by to give the probability error?

Eg. HDOP 4 = ?

Answer 15

Horizontal Dilution Of Precision

13m probability error

HDOP 4 x 13m = 52m

Question 16

Causes of GPS errors:

(5)

Answer 16

Ionospheric and tropospheric interference (UHF signal delays)

Clock bias error (discrepancies on atomic clocks)

Multipath errors (reflected signals)

GDOP (satellite geometry, shallow cut)

Positional or Ephemeris errors (incorrect orbital predictions)

Question 17

Selective Availability (GPS)?

Answer 17

Before 01 May 2000 US dept. Of defence denied civilians GPS accuracy to that of US Military user.

Achieved by disrupting the time + positional data to disrupt signals to provide incorrect positions.

US can still suppress GPS signals to a SPECIFIC region or globally as they own the system.

Question 18

GBAS:
Operation:
Publication for info:

Answer 18

Ground Based Augmentation Service

Station @ precisely known location receives data from satellites in normal way.

GPS position compared to known position indicating an error.

Error is transmitted via MF signals

ALRS Vol. 2

Question 19

SBAS:
Operation:
EU & US geostat sat:

Answer 19

Satellite Based Augmentation Systems

Geostationary satellites transmit correcttions. Greater coverage than GBAS.

EU: EGNOS
US: WAAS

Question 20

How to monitor GPS while underway?

(7)

Answer 20

Number of satellites (min 4)

DOP values

Cross reference other nav methods

Sudden accuracy changes

Use with EGNOS or WAAS support

Keep GPS updated

Understanding GPS limitations

Question 21

Active & passive radar reflector?

Answer 21

Passive reflects signal, Active enhances and returns signal.

Question 22

What is a sound reception system?

Answer 22

Detects and enhances sounds outside, foghorns.

Question 23

What should the telephone to emergency steering be equipped to do?

What should vessels over 500gt have in addition to TTES?

Answer 23

Allow hands free use : loudspeaker or headphones

Over 500gt: Gyro compass heading repeater

Question 24

ECHO SOUNDER
Instructions for setup found in which publication?

Equation for depth:

Answer 24

NP100

Depth = (v x t) / 2

Depth
V = velocity (1500m/s)
T = time

Question 25

When and HOW should an echo sounder be checked?

Answer 25

Using a lead line.

• Refit
• Changes to system
• Annually
• Any doubt

Question 26

ECHO SOUNDERS
What could provide false echoes?

Answer 26

Schools of fish

Kelp / seagrass

Sound interference (aeration, mechanical)

Multiple echoes from hard sea bed

Second trace echoes (deep water previous signal returns after current signal emitted)

Water density (saltwater more dense than FW = more density ~ quicker transmission = shows it is shallower)

Question 27

LOGS
What info do they provide?
List 6

Answer 27

Speed.

Towed / streamed (900 rpm)

Impeller

Doppler

Pressure speed log

Acoustic correlation log

Electro Magnetic log (Faraday Maxwell theory)

Question 28

List 14 items of nav equipment:

Answer 28

Echo sounder

Speed log

GPS receiver

Compass (Gyro or magnetic)

Radar (or reflector under 150gt)

Charts (electronic or paper)

Telephone to emergency steering

Rate of turn indicator

Signalling lamp

Sound reception system in fully enclosed bridge

VDR (over 3000gt)

Search lights

AIS & LRIT (over 300gt)

Rudder, thrust, propulsion indicators