NAV EQUIPMENT

Question 1

Mag Compass checks + Variation and deviation meanings

Answer 1

We must check the observed deviation against our deviation card to ensure that nothing has changed and that the deviation card created during the last compass swing remains accurate.

We keep a record of these checks in our Deck Log Book or Compass Error Record Book in order to monitor deviation over time.

It is also good practice to regularly note both our gyro and magnetic compass headings in the Deck Log Book so that, in the event of a gyro failure, we know which course to steer on our magnetic compass.

Variation is how we quantify the difference between the magnetic north pole and the true north pole, when considered from our location.

The permanent and induced magnetism of the vessel disrupts the magnetic compass. Numerically, deviation is the difference between the north indicated on the vessel’s compass and magnetic north in that location without the influence of the vessel.

Question 2

Mid Atlantic - Mag reading is totally different to Gyro - what are your actions?

Answer 2

Call the Master

Check both compasses to see which one has the error

Question 3

How Can you check your Mag compass in port

Answer 3

You can find a true bearing of an object

Question 4

How to check compass error - mid ocean

Answer 4

You will have to use a sextant to get a

Question 4

How does a gyro compass work

Answer 4

A gyroscope uses a heavy, rapidly-spinning disc, which is allowed to move freely in all three dimensions. This is known as the ‘three degrees of freedom’. When a heavy disc is rotating quickly, it wants to keep pointing in the same direction. This is called a ‘free gyro’ and it leads to two rather interesting phenomena.

Question 5

How to check compass error - coastal

Question 6

Gyro failure actions - what affect does it have on your equipment?

Answer 6

Call the master

Try second Gyro if fitted, if not…

Question 7

Echo sounder set up and errors associated with it?

Question 8

Echo sounder - frequencies associated with deep and shallow water

Question 9

How can you see an error on echosounder screen?

Question 10

How to check an Echo Sounder?

Question 11

How is echo sounder affected by salinity?

Question 12

How does an echo sounder work?

Question 13

GPS - What is HDOP

Question 14

Limitations + errors of GPS

Question 15

Different HDOP values and what do they mean?

Question 16

GPS accuracy check?

Question 17

What is DGPS