Your vessel receives a distress call from a vessel reporting her position as LAT 35°01.0'S, LONG 18°51.0'W. Your position is LAT 35°01.0'S, LONG 21°42.0'W. Determine the true course and distance from your vessel to the vessel in distress by parallel sailing.
• Parallel sailing when two positions are on (approximately) the same latitude • How to find the difference of longitude (DLO) between two longitudes, paying attention to E/W • The relationship between departure, DLO, and cosine of latitude
• Are the two vessels north-south of each other, or mainly east-west of each other? What does that suggest about the approximate true course? • Compute the difference in longitude between 21°42.0'W and 18°51.0'W. Is your vessel east or west of the distress vessel? • Once you have the DLO in minutes of arc, how do you convert that to departure at a given latitude using parallel sailing? Does that give you a shorter or longer distance than the raw DLO in miles?
• Confirm both latitudes are exactly the same so that parallel sailing is appropriate • Be sure you identify correctly which longitude is farther west and which is farther east to choose between 090°T and 270°T • After calculating distance, compare it with both 140.0 miles and 189.2 miles to see which is closest to your computed value
No comments yet
Be the first to share your thoughts!