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Here is All You Need to Know About Doppler Log

Written by Capt Rajeev Jassal on February 27, 2018
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doppler-log-working I am going to be brutally honest with you. To read about how Doppler log works is really a boring task. What makes it confusing also is that there is no clarity in which this topic is usually explained. And believe me, writing about it is equally boring too. But then I received too many questions on Doppler log that I thought of taking up the task of writing on this topic. So let us discuss about Doppler log but first let us look at the regulation by which we need to have a speed log on board. Requirement for Doppler log As per SOLAS Chapter V, Regulation 19.2.3.4, All ships of 300 GRT and upwards and all passenger ships irrespective of size shall be fitted with  a speed and distance measuring device, or other means , to indicate speed and distance through water. doppler log requirement Doppler log is one of such equipment that measures speed and distance through water. EM log is another equipment that measures speed and distance through water but Doppler log is what is usually preferred by the owners. Speed through water is required to be fed into the RADAR and speed through water is what we need to us...

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Comments (16)

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  • MANNU April 22, 2018
    Good day Captain, Yet another master piece. Thank you so much for the awesome blog. This really clears all my doubts & every thing to know about doppler log. I have a furuno doopler on board and makers mention working depth more than 3 mtrs below keel for speed over water. I will put up a caution notice on the radars stating the same, just after reading this blog.
    0

  • Ivor Law July 4, 2018
    My understanding of the Performance Standard, is as follows: "The equipment should comply fully with its performance standard at forward speeds up to the maximum speed of the ship and in water of depth greater than 3 m beneath the keel."
    0

  • AHM WAHIDUZZAMAN July 26, 2018
    Sir, can't the athwart ship movement be found from SB (+ve/-ve) on radar screen? Is it derived from GPS COG & SOG?
    0

  • Mohnish Singh November 16, 2018
    Can you elaborate the difference between Bottom tracking speed ,SOG, STW
    0

  • Faisal khan November 25, 2018
    Sir I have heard one more term related to speed which is observed speed..so could u plz explain difference between log speed and observed speed
    0

  • Marieyessica January 11, 2019
    Sir your blog is really interesting but quite confused. what is the difference between sog from doppler log (bottom track) and sog from the gps.
    0

  • sneha June 29, 2019
    Thnq for sharing Good Info Domestic house hold water meters is a device used to measure the amount of water consumed in a building.
    0

  • B.R. Folmer December 2, 2019
    Why is the velocity of the ultrasonic sound through water of any importance if the only thing measured is the frequency difference is measured. I mean it doesn't matter how long the signal has been underway doesn't it? The doppler shift is only a frequency shift.
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  • Myte January 31, 2020
    Thank you ... I got this topic very well.
    0

  • Amar anand May 4, 2020
    Nice Blog sir
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  • Sachin June 16, 2020
    Dear Sir, Thank you so much for this article and all your work. I have one question, during approaching to berth should DL be set on bottom or speed through water? Thanks.
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  • Dicdiquin, Earl Jasson (Phillipines) July 3, 2020
    Very helpful blog Capt for seafarers like me which have just started on this career. I prefer reading your blogs rather than seeing it in videos. As you have the skill to elaborate your points part by part for us to gain a full understandinf of it. More powers to you and hope you will not be tired to make more blogs.
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  • sanjay March 4, 2021
    Thank you sir for explaining in depth doppler log, can you please describe more on how Janus configuration helps in eliminating Pitching error.
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  • Eduardo Krause April 13, 2021
    1 word: EXCELLENT
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  • FERDOUS September 16, 2021
    Good day sir! i have a doubt . The speed showing along cog by GPS. But While ship get alongside how Janus configuration get activated then to get athwart ship speed?
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  • taymaz October 29, 2022
    is it necessary that speed log connected to ships radar while GPS connected to radar? PSC OFFICERS IN SOME CONTRY EMPHASISI THAT SPEED LOG MUST BE CONNECTED TO SHIPS RADAR.
    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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