At 1614 your GPS position is LAT 37°01.6'N, LONG 75°31.7'W. At 1703 your position is LAT 36°57.0'N, LONG 75°41.0'W. What was the course made good between the fixes?
• Difference in latitude and longitude between the two positions • Using a meridian (latitude) scale to measure distance north-south and an appropriate scale for east-west • Determining true course from the first fix to the second by plotting on the chart
• What is the change in latitude (in minutes) and is the vessel moving generally north or south? What does that suggest about the general quadrant of the course? • What is the change in longitude (in minutes) and, at this latitude, is the vessel moving generally east or west? How does that combine with the latitude change to form a track line? • After plotting both fixes and drawing the line between them, how can you measure the angle from true north through 360° to find the course made good?
• Carefully compute ΔLat and ΔLong in minutes and signs (N/S, E/W) before plotting • Use the correct latitude scale (near the track) to convert minutes of latitude to distance when checking your plot • When measuring the course, ensure the protractor or parallel rulers are aligned with a meridian (line of longitude), not with the track itself, to read the correct true course
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