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

Grant Headifen
Grant Headifen
My vision for NauticEd is to provide the highest quality sailing and boating education available - and deliver competence wherever sailors live and go.
Grant Headifen
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Last updated on July 8th, 2022
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