Determine the great circle distance and...

🔍 Key Concepts

• Great-circle sailing formulas (using latitude and longitude of departure and destination) • Conversion of degrees and minutes to decimal degrees before using trigonometric functions • Relationship between great-circle distance, difference of longitude (DLo), and initial course at the point of departure

💭 Think About

• First, convert both positions from degrees and minutes to decimal degrees. What is the numerical difference in longitude (east vs west), and how will you handle it in your formulas? • When applying the great-circle distance formula, which trigonometric functions (sine/cosine) are used with the latitudes and the difference of longitude? How does this lead you to the central angle, and then to distance in nautical miles? • For the initial course at the point of departure, how does the formula involving both latitudes and the difference of longitude help you determine if the course is more easterly or westerly from your starting point?

✅ Before You Answer

• Be sure you are using nautical miles for distance (1° of great-circle arc = 60 NM). • Double-check the signs of the latitudes (N vs S) and longitudes (E vs W) when plugging into the trigonometric formulas. • After computing the initial course, verify that the result is a true course and falls within a reasonable quadrant given the relative positions of the two points.

Determine the great circle distance and initial course from LAT 08°36.0'N, LONG 126°17.0'E to LAT 02°12.0'S, LONG 81°53.0'W.

9015 miles, 067°T

9076 miles, 079°T

9076 miles, 067°T

9105 miles, 079°T

🔍 Key Concepts

💭 Think About

✅ Before You Answer