At 0900 zone time on 23 September your DR position is LAT 28° 48.0' N, LONG 153° 11.5' W. You are steering course 257° T at a speed of 18.0 knots. You observed 3 morning sun lines. Determine the latitude and longitude of your 1020 running fix. Zone Time GHA Observed Altitude Declination 0915 110°44.9' 40°01.9' S 0°15.8' 0950 119°27.4' 46°22.9' S 0°16.3' 1020 127°00.9' 51°21.7' S 0°16.8'
• Running fix using multiple morning Sun lines and advancing earlier lines to the time of the last sight • Effect of course 257° T and 18 knots on your DR track between 0900 and 1020 (distance run and direction of motion on the chart or plotting sheet) • How advancing lines of position changes the resulting fix latitude and longitude compared with the 0900 DR position
• Sketch the DR track from 0900 to 1020 and mark approximate DR positions at 0915, 0950, and 1020 before doing any detailed plotting. In what general direction is the ship moving (more westerly, more southerly, or both)? • When you advance the 0915 and 0950 Sun lines to 1020 along the DR course and speed, will the final running fix end up generally ahead of, behind, north of, or south of the 1020 DR point? • Compare the answer choices to your expected trend: should latitude be increasing or decreasing from the 0900 DR? Should longitude be increasing (going farther west) or decreasing (going back east)?
• Compute the distance run from 0900 to 1020 using speed 18.0 knots and total elapsed time (in hours) before you look at the answers. • Check whether your final running fix should logically be west or east of 153° 11.5' W based on your course 257° T. • Verify that the change in latitude between 0900 and 1020 is consistent with the southward component of course 257° T (you should be able to rule out any choice that moves you the wrong way in latitude).
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