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Anonymous Sat 12 Apr 2025 02:55:51 No.2038653 View View Reply Original Report

Quoted By: >>2038654 >>2038701

What do you guys know about chart navigation? I have been learning how to do it all week for my 100 ton masters license

Anonymous

Anonymous Sat 12 Apr 2025 03:15:39 No.2038654 Report

Quoted By: >>2038655

>>2038653
I bought a huge one of the Mississippi River between Baton Rouge and New Orleans and framed it.

Anonymous

Anonymous Sat 12 Apr 2025 03:39:18 No.2038655 Report

Quoted By: >>2038658

>>2038654
What's the scale? The smaller the number, the more detailed it is. 1:50,000 or less is a harbor chart, which is the most detailed. Means 1 inch on the chart is 50,000 inches of the earth..

Anonymous

Anonymous Sat 12 Apr 2025 04:12:18 No.2038658 Report

Quoted By: >>2038659

>>2038655
It's 1:40,000 and I have it printed out on a huge 4'x5' or so sheet.

https://historicalcharts.noaa.gov/pdfs/11370.pdf

Anonymous

Anonymous Sat 12 Apr 2025 04:28:55 No.2038659 Report

Quoted By: >>2038660

>>2038658
That's neat.
It's a very old chart but still fun to look at. It's difficult to find your fix because it doesn't have lat and long on the sides and top/bottom
It's also pretty goofy that true north keeps moving around and that it isn't just up

Anonymous

Anonymous Sat 12 Apr 2025 04:33:37 No.2038660 Report

Quoted By: >>2038690

>>2038659
There are mile markers on the river, so that should hopefully make it pretty easy to keep straight where you're at.

They move the north heading on the chart because the river starts being near perfectly true/magnetic north/south(it is the same in Baton Rouge) and the river then runs nearly east/west in New Orleans. It lets them keep about 75 miles of navigation on one chart.

Anonymous

Anonymous Sat 12 Apr 2025 15:59:23 No.2038690 Report

Quoted By:

>>2038660
Oh, that's very interesting. I did notice that true and magnetic were basically the same and that the variation was basically none existent from compass rose to compass rose.
We were taught to look up all the local knowledge in the coast pilot. There is probably a note on the chart somewhere about what chapter to go to.

Anonymous

Anonymous Sat 12 Apr 2025 19:58:00 No.2038701 Report

Quoted By: >>2038744 >>2038745

>>2038653
Quite a bit. I'm only a recreational sailor but a professional mathematician so I get autistic about spherical geometry and manually estimating drift and such things. What's your favorite thing/what specifically are you studying?

Anonymous

Anonymous Sun 13 Apr 2025 03:48:44 No.2038744 Report

Quoted By:

>>2038701
For the 100 ton test I have to be able to plot fixed points using GPS coordinates and 2 point bearings, plot way points, calculate drift and set current speed using DR points, calculate ETA, and calculating my course lines. Everything has to be within 2 tenths or 2 degrees.
It's not that hard, as long as you do everything in order. I only have to know 3 formulas to calculate time, distance, or speed. It's all been pretty neat to learn.

Anonymous

Anonymous Sun 13 Apr 2025 04:04:02 No.2038745 Report

Quoted By:

>>2038701
Also, calculating drift and set of the current is pretty easy. You take a fixed point, and take note of the time. You then plot a DR position at whatever time you want. Once it gets to whatever time you plotted your DR position to, take another fixed position, using bearings or GPS or even the stars if you are that good, to see we're you actually ended up. Then measure the distance between the 2 points and divide your distance by the time, multiply it by 60 and that is the speed of the current, in knots. Whatever direction it pushed you is the currents direction.

Anonymous

Anonymous Sat 26 Apr 2025 15:05:01 No.2039002 Report

Quoted By: >>2039006

Bump.
I passed my test and now have a 100 ton masters license with a near costal

Anonymous

Anonymous Sat 26 Apr 2025 16:15:23 No.2039006 Report

Quoted By:

>>2039002
Congrats anon

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