Test Question: How to Determine Speed and COG

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Try to answer this coastal navigation question:

At 1035 your GPS indicated a position of LAT 41° 05.3’N and LONG 72° 33.7′ W. At 1103 your GPS indicates your position to be LAT 41°09.0′ N and LONG 72° 40.0’W. What was your SOG and COG?

Here is the excerpt of the chart that you will need

Answer: Posted below. But give it a go yourself first – really!

Consider taking the NauticEd online Coastal Navigation Course

Answer:

See chart plot here

From the plot, the distance is 6nm.

Time is calculated by realizing that 1103 = 1063. Thus:

1063
– 1035
0028 minutes

28 minutes is 28/60 hours = 0.467 hours

SOG (Speed Over Ground) = 6nm/.467 hours = 12.85 nm/hr (knots)

From the plot, and overlaying a Bretton plotter compass dial, the COG (Course Over Ground)  is 307.5 deg T

Boom Done!

SOG and COG example

SOG and COG example

Author

  • Grant Headifen

    My vision for NauticEd is to ensure that families and friends get out on the water not only safely but with true COMPETENCE, confidently savoring every moment of their valuable time.

    Achieving this means being the pinnacle of sailing and boating education—offering comprehensive multi-media theoretical instruction coupled with hands-on, on-the-water training through our global network of American National Standards Instructors. We steadfastly avoid becoming a mere certification mill; our focus is on delivering genuine competence, ensuring our students are well-prepared for enjoyable, real-world boating experiences.

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Last updated on July 8th, 2022
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