Test Question: How to Determine Speed and COG

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

Coastal Navigation Course
Take the NauticEd Coastal Navigation Course


See chart plot here

From the plot, the distance is 6nm.

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

– 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

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