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Position Fixing: The Most Important Element of Passage Planning

Written by Capt Rajeev Jassal on May 6, 2017
54
position fixing ship by bearing Heavy traffic, extra Look out posted, hours of darkness. Suddenly the GPS is gone !!! Ever experienced this ? Believe me when it happens, you start doubting each and every equipment. Even the ones which may be working fine at that moment. Is the gyro giving correct heading ?  Is the echo sounder showing correct depth ? You will doubt everything !!! That's not good. You will loose the sense of direction. And you would have tiny amount of time to regain the sense and act in a way that is right. The entire navigation depends upon knowing the position of the ship. This is one of the most important task of a navigator. But when I say position, I do not only mean GPS position. There are many other ways of plotting the ship's position. And as with the situation of GPS failing, we must be ready to switch to other methods of position fixing. Before we proceed with discussing these methods, I must discuss a term which is so much a part of passage planning. The term is "position Fixing Interval". Position Fixing Interval "Position fixing interval" is the maximum interval between two position fixes. So if in a particular section of the passage, we have agreed to the PFI of 01 hour, we must plot the ship's position at least every hour. But how do we decide the position fixing interval ? For...

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Comments (54)

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  • Sujay May 7, 2017
    0

  • Krishna Patel May 7, 2017
    A very good effort sir. Very crisp and simple to understand.
    0

  • V.B.Kripalani May 7, 2017
    An excellent and understable way prsented.You must be in teaching business. Please meet another old teacher.Do keep in touch.
    1

    Rajeev Jassal May 15, 2017
    Thank you Sir. No, I am not into teaching. I am just trying to give the salt back to sea..

  • Raman Kumar jha May 14, 2017
    Dear Sir, very good morning !!! Thanks for easily explain and very useful. Regards, Raman
    1

    Rajeev Jassal May 15, 2017
    Glad you found it useful Raman..

  • Rajeev Jassal May 15, 2017
    Thank you Krishna..
    0

  • Vijay Thapa July 5, 2017
    Sir, Excellent effort ....for made simply understand..Thank you very much, Sir.
    1

    Rajeev Jassal November 17, 2017
    Glad you found it useful Vijay...

  • Ngo Tan Thai Duong July 13, 2017
    Dear sir, I would like to ask you that if you have time, can you write a post about the radar techniques in using to manouever the ship during the coastal navigation. I really like it and as I know the ability of the 2nd mate will be identified through his using radar technique. Thanks in advance.
    1

    Rajeev Jassal November 17, 2017
    I will write on this topic in near future...

  • Peter December 6, 2017
    Many thanks Capt. Rajeev, excellent piece. Allow me a question please. VIQ states that parallel indexing should not be used with floating objects, but what about clearing bearings? I see that many navigators use Clearing Bearings with buoys. Is that acceptable?
    0

  • Marc January 8, 2018
    For what? Flat earth or undependable thousand of satellites that cant give GPS. Flat maths sure help to calculate :)
    0

  • Clint January 25, 2018
    Awesome!
    0

  • siddharth February 14, 2018
    do we need to put pfi intervals on ecdis chart as well as it is being done by the use of gps labels on ecdis? For instance i am getting time label of 10 mins each on my ecdis track and hence i am monitoring my position continuously still do i need to put pfi interval on user map?
    0

  • Dhairya joshi February 26, 2018
    Sir can we plot radar bearings directly to chart?
    0

  • Kenneth Carl April 12, 2018
    thank you for this sir, how about plotting celestial observation in furuno ECDIS?
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  • PARK JANG KYU June 21, 2018
    Dear Capt. Rajeev Jassal
    0

  • Kenneth September 4, 2018
    Hi, how do we input celestial observation or position in the ECDIS?
    0

  • CAPTAIN GILBERT LEE December 7, 2018
    good stuff. https://www.youtube.com/playlist?list=PLafMfVypK6pOlSQ8ukxo_MXEb2pWxCDZO
    0

  • Captain Gilbert Lee December 7, 2018
    good stuff. https://www.youtube.com/playlist?list=PLafMfVypK6pOlSQ8ukxo_MXEb2pWxCDZO
    0

  • TONY March 5, 2019
    how would i find out position plotting interval for a leg?
    1

    JUNIMAR March 9, 2020
    In open sea, position fixing interval is 1 hour. In coastal waters (when vsl is within 12 NM from shore), for ELECTRONIC CHARTS at interval of not more than 30 minutes with cross checks in between. For PAPER CHARTS, GPS positions to be verified by using simple formula for identifying PFI in coastal water: PFI= 1/2(D) ÷ (V/60), where D is the nearest distance of the shore or obstruction along your LEG and V is the vessel SPEED or planned speed of your passage.

  • Moh March 26, 2019
    Please in my deck logbook there is method to get position by obs or ac'nt Please can you explain what is the meaning of ac'nt
    0

  • Dhananjay July 11, 2019
    Pls ezplain about lop in ecdis
    0

  • Ferobe July 9, 2020
    Thank you for sharing your knowledge
    0

  • Mayank July 22, 2020
    One thing I have noticed you have skipped the celestial fix plotting on ECDIS , would appreciate if you can explain how celestial fix was plotted on paper chart and how to do the same on an ECDIS ,so that we can co relate e.g. Longitude by Chronometer, Mer-Pass and Intercept . All 3 methods . I am using Transas Navisailor 4000 and I have no clue about it.
    0

  • Shubham August 12, 2020
    Can i take the fix using a bouy? If yes then which buoy?
    0

  • pawan kumar September 1, 2020
    Hello sir can you please tell the position plotting interval in ecdis
    0

  • Alok Ranjan November 26, 2020
    Thank you very much capt sir for ur efforts, it's really simple to understand .
    0

  • Myo Min Htet December 6, 2020
    Very appreciate for sharing your precious knowledge not only present post but also all post from MySeaTime blog. Most of comfuse things are clear after I read your post. Thank you sir.
    0

  • Alan January 2, 2021
    Sir can you pls fiil in some more info on the use of eho sounder and logs when used as a means of position fixing
    0

  • Nad Rosero January 15, 2021
    Dear sir, Thanks for sharing this knowledgeble information, one of the best idea that I/we must be learned as a seafarer. ????
    0

  • Harshit January 28, 2021
    Can someone advise can we plot position using light buoy??? If we can in which manual is it written??
    0

  • Harshit January 28, 2021
    In my previous comment I want to mention light vessel instead of light buoy..
    0

  • MD. RABIUL HOSSAIN April 6, 2021
    It is very easy and full of information that you are provided on each topics, which is very helpful for COC exam as well as for practical sea life. Tks indeed.
    0

  • NEOFYTOS ADAKTYLOS April 8, 2021
    What about DR fixes?
    0

  • Levi Armstrong May 19, 2021
    It's great that you mentioned that GPS fixes help automatically fix intervals and record the boat's position and not be over-reliant on it. My dad and brother are going on a fishing trip this weekend to the sea. I'll share this with them later. Thanks! https://wharf-marine-sales.myshopify.com/products/garmin-gpsmap-743-chartplotter-preloaded-us-canada-bahamas-bluechart-g3-lakev-g3-010-02365-01?_pos=1&_sid=581275453&_ss=r
    0

  • ANEESH July 1, 2021
    Thank You Very Much Sir. Very nicely explained all aspects of position fixing.
    0

  • bahaa gad abd elmaksoud September 29, 2021
    Thanks alot for your time and efforts Really perfect
    0

  • Raul October 19, 2021
    1. If you are in SSW how many degrees to the opposite side, and explain why and what Quadrant by applying boxing the compass? 2. Explain carefully the procedure why boxing the compass applying 11 +1/4 degrees, in order to determine and compensate by 360 degrees. 3. What is the Basic procedures to determine the object thru celestial observation and by bearing object with three methods to get the fix position. Explain? 4. 360 degrees is equal to 000 degrees north, in that location what action to be taken in order to compensate your gyro course by 315 degrees when you are turning to west and you going to locate the variation and deviation?Explain. 5. Explain what is the Latitude and Longitude and their functions? in relation to determine the fox position when you observing the bearing object thru compass especially the celestial bodies such as the sun, moon, stars, etc
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Capt Rajeev Jassal

About Capt Rajeev Jassal

Capt. Rajeev Jassal has sailed for over 24 years mainly on crude oil, product and chemical tankers. He holds MBA in shipping & Logistics degree from London. He has done extensive research on quantitatively measuring Safety culture onboard and safety climate ashore which he believes is the most important element for safer shipping.

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