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How a Marine Sextant Helps in Getting Ship Position ?

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SextantIn the age of Google maps, GPS and AIS, there is something in the wheelhouse that looks so outdated. I am talking about sextant and getting the position of the ship by sextant. Now before you yawn and find some more sexy navigation topic to jam on, hear me out. Sextant has something unique that all the advanced technologies cannot match. It can give you your accurate position without relying on any electronic aid or satellite. That is the reason sextant has been there and as far as we can tell, it always will be. But there is also a drawback. To get a position from the sextant requires some calculations and expertise in handling the sextant. Also, the position is not instant read out like in modern equipments. But more you use the sextant, more these drawbacks are marginalized. Now you may know all the calculations of the sextant. You may know about long by chron, Mer-pass and all other calculations to get the ship's position. But if you don't know how the hell an equipment like sextant can get us our position, you are missing everything. And anyone who wants to learn just that, they need to start with something very basic. Position lines. Position Lines I am going to assume that you know nothing about "position lines". That is totally OK. I will spell it out for you. A position line is a line on which lies a point where ...

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Comments (21)

  • Snehasish Padhi September 30, 2017
    Respected sir , I really dnt having any appreciable words in my treasure just to dignify you ...Our Expertise must someway or other will be always count on you sir...You making things so simple so as an damn idiot can understand well
    1
    Rajeev Jassal October 2, 2017
    Thanks, Snehashish...
  • arbaaz October 11, 2017
    sir, can you plz tell me why IG is not used in bunker tanks but used in cargo tanks?
    2
    Rajeev Jassal October 19, 2017
    The flash point of bunker oil is more than 60 C and it is not flammable...
    aman arya December 23, 2017
    but sir we use ig if we carry fuel oil in cargo tanks.
  • Avinash Karnad October 17, 2017
    Sir, your explanation is better than the textbooks!
    1
    Rajeev Jassal October 19, 2017
    Thanks, Avinash...
  • rohit November 10, 2017
    sir explain about all bridge equipment
    1
    Rajeev Jassal November 17, 2017
    I will write on bridge equipments in near future...
  • Piyush November 18, 2017
    Very nice and explanatory approach ,must say many many thanks and wish for more knowledge of many forgotten equipments of a board ship .
    1
    Rajeev Jassal November 19, 2017
    Thanks Piyush...
  • RAJESH PRASAD February 17, 2018
    Your explanations are simple and legible. God bless you sir.
    0
  • RAJESH PRASAD February 17, 2018
    Sir explain damaged stability and ability to calculate predicted stability.
    0
  • ebrima kebbeh October 4, 2018
    I am from Gambia and really appreciate your work, it is simple and easy to understand. Many thanks
    0
  • vikram singh November 29, 2019
    sir your explanation is so easy to understand.we appreciate your effort sir
    0
  • Aditya Rai January 19, 2020
    Sir why position line is always perpendicular to azimuth?
    0
  • Darlos January 22, 2020
    I red about sextant on many websites and this is the best and simple note I found, thanks. Can we get pdf version ?
    0
  • kursat ozer February 25, 2020
    Thank you for your kind and good effort. You explain very easy to understand.
    0
  • Yasir September 1, 2020
    I have read your articles they are good.. there is one guy asking for sextant.. why it is 1/6th of circle why not half of cirlcle or why not full circle ? Your answer regarding this will be helpful to us..
    0
  • Gaurav Bahuguna September 13, 2020
    Respected sir all your blogs are really amazing and informative. Keep writing and enlighten us always sir.
    0
  • Ilgın Özgül January 14, 2021
    Excellent. Thank you for sharing your information with us, sir.
    0
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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