# Navagation equations

I need help learning how to solve these navigation problem can anyone help me out.

Exp:
At 1032 on 24 June, you pass the Carolina Landing Light (508.8 aph). What has been the average current since 2350, 23 June if you have been making turns for 9.0 mph?

If you can help I would greatly appreciate it.

Patrick

Patrick,
Since the question is looking for the average current for the preceding 13 hours or so, I would be referring to the Tidal Current Tables in the back section that displays the current graph. If you inspect this table you’ll find a number of graphs that list points along your route and others eg; Chesapeake Bay, Hudson River, Long Island Sound, etc.
The colors/shading for “flood” and “ebb” are slightly different. On the side margin you’ll find “speedlines” marked with speed increments which are used by walking them with a parallel ruler onto the graph. If you walk the [B]9 knot[/B] line over your time at Carolina light, it will fall within or across the tidal current cycle and you should be able to determine an average current speed.
This graph is generally used when you want to know what “speed to use” to carry the current a long distance, say Chesapeake Bay Entrance to Baltimore. Or if you want to time your arrival for slack at a specific point along the route where you wish to avoid any adverse effect from too much current, like The Race at the eastern end of Long Island Sound…
It’s not terribly complicated, and it comes in handy. Read the instructions on the graph’s page and give it a try.
I hope this has been helpful.
bb

One other thing I thought of that may be useful. If you have the distance traveled from 2350 23June to 1032 24 June, it’s a time-speed- distance problem. The distance divided by 9 kts would give you the time in zero current. Eg:[B] 200nm/9k = 22.2hrs[/B] If you covered the distance in less than 22.2hrs, you had a fair current. If it took longer than 22hrs, you had an adverse current. Use the TS&D formulas to determine your speed made good. If your time en route took less time than the predicted period, the difference is the average [I]fair[/I] current you experienced. B200nm / (t)20hours = (s)10kts[/B], in this case your average fair current was 1kt.

[QUOTE=Pcrooks;48428]I need help learning how to solve these navigation problem can anyone help me out.
Exp:
At 1032 on 24 June, you pass the Carolina Landing Light (508.8 aph). What has been the average current since 2350, 23 June if you have been making turns for 9.0 mph?
If you can help I would greatly appreciate it. Patrick[/QUOTE]

[B][U]IMHO[/U][/B]…as previously stated this is indeed a TSD “plot” problem…correct USCG answer is[B] 0.5 MPH[/B]…for clarification try working thru the problem “backwards”…hope this helps?