Chartwork (Fixing Position)

Question 1

Range of light from Vertical sextant angle

Answer 1

Height of light (from Chart or ALLFS)

Height of light/Tan x (VSA)
Bring to Nm by dividing the result by 1852

1852m is equal to 1NM

OR we use the Range by VSA table in Norries

Range and the Bearing gives you the Fix

Question 2

What allowances may we have to make for a VSA?

Answer 2

Tide: When accounting for tide, add the tidal difference between MHWS and the current state of tide

Index Error on the Sextant

Correction for the HOE (Norries assumes the HOE is 11m) here we make a correction for DIP

ALLFS has a height of the OBJECT, Chart has a height at the centre of the LENS

Question 3

Horizontal Sextant Angle Pro Forma Method 1: station pointer
(Can be with a compass)
Can be used on the chart with a station pointer

Answer 3

Method 1
1. Measure angle from Point A to Point B
2. Measure angle from Point B to Point C
3. Use a station pointer to get your position
When the three limbs line up with the points, put a dot in the middle of the station pointer.

Question 4

Beam Bearing

Answer 4

090 Degrees from Course Steered
Port side of vessel, CoSt - 090
Stbd side of vessel, CoSt + 090

Question 5

Gyro High

Answer 5

Take off to get to T

Question 6

Gyro Low

Answer 6

Add to get to T

Question 7

Running fix Pro Forma

Answer 7

1. Plot initial LOP
2. Plot an EP anywhere in safe water on that EP, Time Stamp
3. Lay off water track for given time interval >
4. Lay off tidal vector for same time interval&raquo_space;>
5. Transfer initial LOP through your second EP at the END of the tidal vector
6. Lay off second bearing off second object, pass it through transferred LOP
7. This is your FIX

GROUND track length and course is EP to EP
Transfer GT through Fix back to initial LOP to find Initial EP&raquo_space;

Question 8

Tide experienced Pro Forma

Answer 8

1. Plot initial Fix
2. Plot water track for given time interval >
3. Plot second given position Fix
4. Join W/T to second position Fix&raquo_space;>
5. Lay off G/T between two points&raquo_space;

Question 9

Plot a CTS pro forma

Answer 9

1. Plot initial position
2. Plot end position
3. Join two positions, this is your GT, COG, CMG&raquo_space;
4. Lay off Tidal vector from initial position&raquo_space;>
5. Arc off boat speed for given time interval (WT) >
6. Add counteraction for Leeway to this track (Off chart) this is your CTS

Question 10

Plot an EP Pro Forma

Answer 10

1. All calculations first
2. Plot position
3. Lay off W/T for given time interval, taking into account the effects of LEEWAY >
4. Lay off tidal vector for same interval&raquo_space;>
5. Plot EP with time
6. Join initial position fix to EP, to give CMG, COG&raquo_space;

Question 11

Admiralty publications that can be used for passage planning

Answer 11

Chart catalogue
Navigational charts
Sailing directions/ pilot books
ALRS
List of lights and fog signals
Tide Tables
Ocean passages for the world
Routeing charts

Question 12

10 Items of useful information found in Admiralty publications for passage planning

Answer 12

VTS stations to call
Radio Information required in report
requirements for pilots
details of navigation lights
Height of tide for port entry
Recommended routes
Radar conspicuous objects for position fixing
Predominant wind for ocean crossing
Port facilities
Location of pilot boarding stations

Question 13

Sections in the Weekly edition of the Admiralty Notice to Mariners

Answer 13

I explanatory notes. Publications list (charts affected this week)
II Updates to Standard Nautical Charts
III Reprints of NAVAREA I Navigational Warnings
IV Updates to ADMIRALTY sailing directions
V Updates to ADMIRALTY list of Lights and Fog Signals
VI Updates to ALRS
VII Updates to miscellaneous ADMIRALTY nautical publications
VIII Updates to ADMIRALTY digital services

Question 14

Procedure for checking a chart is up to date once receiving the weekly notices

Answer 14

1. Obtain weekly NM from an approved provider
2. Use section I to update our chart outfit (ensure correct charts on board)
3. Use section II to see which charts are affected
4. Gather Equipment for correcting
5. Np5011 Np 133A Np294
6. Check bottom left for corrections applied until now
7. Apply correction
8. Place correction number at the bottom of the chart
9. Record this in the chart correction log

Question 15

Ways of Fixing your position:

Answer 15

Primary fix, GPS
Cross checked by:
3 point fix
Radar Range and Bearing
3 Radar Ranges
VSA
Horizontal Sextant Angle
Dipping/Raising Height
Bearing of conspicuous object with a depth contour
Running Fix

Question 16

How often do we fix our position?

Answer 16

Often enough that the ship will not get into danger between fixes. This is heavily depended on the speed of the vessel, SAFE SPEED (rule 6)

Question 17

How do we check our Echo Sounder?

Answer 17

Throw a lead line over the side, in line with the transducer.

Question 18

How do we do a dipping height?

Answer 18

1. Find height of object in List of Lights or from Chart
2. Take bearing of light
   Formula = 2.08 × (√Elevation + √Eye height)
   Or Distance of the sea horizon table in Norries
   Answer to this gives you a range
3. Bearing + range gives you a fix

Question 19

What is a PI

Answer 19

Parallel Index, a way of continuously monitoring a ships cross track tendencies, in relation to a pre determined passage plan

Question 20

What can a PI also do?

Answer 20

Back up or confirm a GPS position, NOT A FIX

Question 21

Define Tides:

Answer 21

Periodic vertical movements of the water on the Earths Surface
Caused by the gravitational pull by the Sun and the Moon

Question 22

Define Tidal Streams

Answer 22

Periodic movements of the water that result from the tides

Question 23

Define Height of the Tide:

Answer 23

Vertical distance at any moment between Chart Datum and the current water level

Question 24

Define Tidal Range:

Answer 24

Difference between the High and Low Tide

Question 25

Define Spring Tides:

Answer 25

Higher highs and lower Lows, Greater range

Question 26

Define Spring Tides

Answer 26

Lower highs and higher lows, L ess range