🔍 Key Concepts

• Using a range (two charted objects in line) to find gyro error • The relationship between true, magnetic, and compass headings (T–V–M–D–C) • How to decide if an error or deviation is east or west ("compass least, error east; compass best, error west")

💭 Think About

• From the chart, what is the true bearing of Block Island Southeast Point Light in line with the Aerobeacon at your position, and how does that compare with the observed 308.5°pgc? • Once you know the gyro error, what is your true heading when the helmsman reports 106°pgc, and what is the corresponding magnetic heading using the local variation? • Comparing the magnetic heading with 119°psc, is the compass reading higher or lower than magnetic, and what does that say about whether deviation is east or west?

✅ Before You Answer

• Verify the true bearing of the range from the chart and use it consistently. • Check your signs and order for the T–V–M–D–C steps; write them in a line so you don’t mix them up. • Before picking an answer, confirm whether the compass reading is greater or less than magnetic to decide if deviation is E or W.