At 1218, on 16 March, you are passing the Vicksburg Gage (mile 437.0 AHP). What has been the average current since 0630, 15 March, if you have been making turns for 8.0 mph?
• Speed through the water vs. speed made good (SOG) on a river with current • How to compute average speed from total distance traveled and total time • Relationship between vessel’s turns (8.0 mph) and the river’s current (upstream vs. downstream)
• From 0630, 15 March to 1218, 16 March, how many hours (in decimal form) have actually passed? • Once you know the total elapsed time, what two distances do you need: (1) distance you would have gone in still water at 8.0 mph, and (2) the actual river miles you advanced between the starting mile and mile 437.0 AHP? • How do you express the current as the difference between speed through the water and speed made good over the ground?
• Be sure you have the correct total elapsed time between the two dates before doing any speed calculations. • Confirm the distance made good in river miles from your starting position to Vicksburg Gage (mile 437.0 AHP). • Check that your final current value is reasonable: it should be much smaller than 8.0 mph and match the sign/direction (helping or opposing) implied by your track.
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