Calculating Azimuth

When taking the Gyro or Magnetic bearing you must know also the following:

• Time in GMT, so recalculate the ships time back to GMT
• Date
• Latitude and Longitude
• Gyro course (GC)
• Magnetic course (MC)
• Variation taken from the chart
  
  

In the Brown’s Almanac look for the correct date and at the correct time (GMT) for the GHA and declination for the body you’ve taken the bearing of.

If longitude is E then add to GHA to get LHA
If longitude is W then subtract from GHA to get LHA

LHA is always given as W-ly length. If LHA is bigger than 180° (degrees) bring back to E-ly length, with formula: 360°-LHA=E-ly length.

P = LHA d = declination b = latitude (N/S)

If b=d and P>90° then A+B, if P<90° then A-B or B-A
If b≠d and P<90° then A+B, if P>90° then A-B or B-A

In table A search for value at Br(latitude) and P
In table B search for value at d(declination) and P
In table C search for Br(latitude) and value A/B to find TB(true bearing)

If P > P90° then T is sharp (top of table)
If P < P90° then T is blunt (bottom of table)

Example:
01.09.06 at 04:13BT 04:13BT equals 06:13GMT Object is the Sun
Lat: 49°29.6N (N is positive (+) and S is negative (-))

Lon: 000˚02.8W (W is negative (-) and E is positive (+))
GC: 149˚

MC: 151˚

var: 2.5˚W
Gyro bearing (GB): 086˚

0600 269˚58.3N table A value: 0.06
0013 3˚15.0 (+) table B value: 0.14 -
GHA 273˚13.3 table C value: 0.08 (b=d and P<90˚)
Lon 000˚02.8W (-) search in C with LAT (br) and value gives
LHA 273˚10.5 (>180˚ so 360˚-273˚10.5→) TB (true bearing) of: 087˚
LHA’ 086˚49.5 E-ly length
Dec 008˚19.0N

With formulas:
TB – GB = GE → 087˚ - 086˚ = 1˚ GC = gyro course TC = true course
GC + GE = TC → 149˚ + 1˚ = 150˚ MC = magnetic course GE = gyro error
TC – MC = CE → 150˚ - 151˚ = -1˚ GB = gyro bearing CE = compass error
deviation = CE – var → -1˚ - -2.5˚ = +1,5˚ TB = true bearing var = variation

Remember: As a duty officer you have to test compasses errors at least once every watch. If the horizon is cloudy, you have to take bearing and calculate the azimuth as soon if you see the sun or moon. Stars are also used but the sun and moon are the easiest to take bearings from.

Correcting charts and books [2]

Image 4: Logos of the Admiralty

O nboard we have charts and books. These need to be update in order to give the most recent information. To update, the Admiralty, publishes a weekly NtM[3]. In this NtM all the correction for that week for the concerning charts and books are found. On the next pages an explanation will be given on how to update charts and books onboard.

1. When you receive the new NtM edition, enter the number of the edition and date received in the list of weekly editions found in NP133A onboard. See image 5.

Image 5: List in NP133A

1. After entering the info in the list, you continue with Section I Explanatory Notes and Publications List in the NtM. This section contains the following:
1. Section I: List of new charts, new editions and navigational publications published, and any chart withdrawn during the week.
2. Section IA: Published monthly and contains a list of Temporary and Preliminary notices cancelled, previously published and still in force.
3. Section IB: published quarterly and consists of lists of current editions of:

i. Sailing directions and their latest supplement

ii. List of Lights and Fog Signals

iii. List of Radio Signals

iv. Tidal Publications and

v. Digital Publications

1. In this section you highlight, by marker, the chart number from your, onboard, collection and check if there are new charts in your trading area. When finished with the marker, update that info in your list of charts and chart catalogue in NP131. In image 6 you see an example of section I.
   
   

Image 6: Example of section I

1. Section II Updates to Standard Navigational Charts.
   This section contains the next subjects:
1. The permanent Admiralty chart updating notices
2. Temporary (T) and Preliminary (P) Notices and
3. Blocks and depth tables at the end of the section
2. In this section, in the part Index of charts effected, you highlight by marker the chart number from the onboard collection. In image 7 you see an example of this part.

Image 7: Example of section II

1. In the log, in NP133A, enter the number of the notices against any effected chart. Turn to the end of the section to check for Temporary and Preliminary notices, which you have to put later in a special folder for T & P notices in use. In image 8 you see the log as in NP133A.
   
   

Image 8: The log as in NP133A

1. Then find the tracings for the effected charts and update the charts. In image 9 you see an example of a tracing. Tracings show graphically the update required to make in a chart by NM number. It enables you to prick the positions onto the chart for correction. For examples on how to keep you Admiralty product up to date, see NP294, Chapter 5 from page 27.

Image 9: Example of a tracing

1. In a tracing, information is given. It will tell you the following:
1. The previous update of the chart. You have to check on the chart of that correction was made.
2. Is the chart a new chart (NC) or a chart with a new edition (NE). The month and year of publishing are shown. You have to check this on the chart as well, in the left down corner.
2. When a correction from the tracing is done, you put the correct NM number in the left down corner of the chart, as seen in image 10.
   Warning: Always check if the previous correction has been made. If not, you will have to find the correction and still correct the chart.
   
   

Image 10: Corrections on a chart

1. Section III Reprints of Navigational Warnings.
   This section lists the serial numbers of all NAVAREA messages in force with reprints issued during the last week.
1. You have to check the printed messages, file them and note them down by area in the folder containing the NAVTEX, NAVAREA and weather fax prints. Also you have to update the previous information on the file and any notations made on the charts.
2. Section IV Amendments to Admiralty Sailing Directions.
   This section contains amendments to Admiralty Sailing Directions published during the last week. The full text of all notices is published yearly.
1. Cut and paste the correction in the right Sailing Direction or follow the instructions given in the notice. If a correction has been put in the book, write the number and date of correction on the front page of the book.


3. Section V Amendments to Admiralty Lists of Lights and Fog Signals.
   This section contains amendments for the List of Lights books.
1. Cut and paste the amendments in the book or follow the given instruction in the notice. If a correction has been put in the book, write the number and date of correction on the front page of the book.
4. Section VI Amendments to Admiralty Lists of Radio Signals.
   This section contains the correction for the Lists of Radio Signal books and a cumulative list of the amendments of the current editions of ALRS which are publishes quarterly.
1. Cut and paste the amendments in the book or follow the given instruction in the notice. If a correction has been put in the book, write the number and date of correction on the front page of the book.
5. In image 11 you can see the front page of a NtM.
   
   

Image 11: Front page of a NtM

Chapter 4 | On deck

I n this chapter:

» General cargo information

» Cargo operations

» Lashing equipment

» Mooring operations

» Gangway watch

» Deck maintenance

» Anchor operations

» Communication procedures

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Дата добавления: 2015-11-14