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Find CURRENT or the SET AND DRIFTPowerPoint Presentation

Find CURRENT or the SET AND DRIFT

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The boat has been pushed from where you wanted to be (the DR line) to its actual position on the Track.

Find CURRENT

or the

SET AND DRIFT

You can recognize this type of problem by the form of the answers.

089°T 1.2knots

Find your starting point

Draw in your DR LINE which is your INTENDED course.

This is the line that you THINK the boat is following over the ground.

DR

0900

x

x

Draw in your TRACK LINE.

This is the path over the ground that the boat is ACTUALLY following.

DR

TRACK

0945

0900

x

x

Find out where you THOUGHT you would have been at (in this case 0945) the time the FIX was taken.

DR

TRACK

0945

0900

x

x

Find out where you THOUGHT you would have been at (in this case 0945) the time the FIX was taken.

To do this use DSTreet D=S*T

S=BOAT SPEED

T=ELAPSED TIME 45minutes or 0.75 hr. in this example.

Due to boat speed alone, the boat would be somewhere on this CIRCLE having a radius of the D found.

DR

TRACK

0945

0900

x

x

x

Find out where you THOUGHT you would have been at (in this case 0945) the time the FIX was taken.

To do this use DSTreet D=S*T

S=BOAT SPEED

T=ELAPSED TIME 45minutes or 0.75 hr. in this example.

This point is measured from the starting point ALONG THE DR LINE

DR

TRACK

0945

0900

x

x

x

Complete the triangle by connecting the DR position charted to the FIX.

Notice that they are both at 0945.

DR

TRACK

0945

0900

x

x

x

Complete the triangle by connecting the DR position charted to the FIX.

The boat has been pushed from where you wanted to be (the DR line) to its actual position on the Track.

This is the direction of the current or the SET

DR

TRACK

PUSH

0945

0900

x

x

x

Complete the triangle by connecting the DR position charted to the FIX.

The boat has been pushed from where you wanted to be (the DR line) to its actual position on the Track.

This is the direction of the current or the SET

DR

TRACK

PUSH

0945

0900

x

READ THIS SIDE OF THE COMPASS

x

x

Complete the triangle by connecting the DR position charted to the FIX.

The boat has been pushed from where you wanted to be (the DR line) to its actual position on the Track.

This is the direction of the current or the SET

DR

TRACK

0945

0900

x

x

x

Complete the triangle by connecting the DR position charted to the FIX.

This is the direction of the current or the SET

In this case 115°T

DR

TRACK

0945

0900

x

x

x

Now we want to find the speed or DRIFT.

There are two ways to do this.

The first is by plotting.

The second uses DSTreet.

DR

TRACK

0945

0900

x

x

x

To use the PLOTTING METHOD we need to draw a second triangle.

To do this use DSTreet D=S*T

S=BOAT SPEED

T= ONE HOUR

This will tell us where we THOUGHT we would be in ONE HOUR.

REMEMBER that this is plotted on the DR LINE

DR

TRACK

1000

0945

0900

x

x

x

To use the PLOTTING METHOD we need to draw a second triangle.

Place the parallel rule on the SET LINE found previously and walk this angle to the ONE HOUR DR position.

Draw a line connecting the DR line to the TRACK line.

DR

TRACK

1000

0945

0900

x

x

x

To use the PLOTTING METHOD we need to draw a second triangle.

Place the parallel rule on the SET LINE found previously and walk this angle to the ONE HOUR DR position.

Measure the distance (D) along this line.

MEASURE THIS DISTANCE

DR

TRACK

1000

0945

0900

x

x

x

To use the PLOTTING METHOD we need to draw a second triangle.

Use this value of D and

ONE HOUR for T to find the DRIFT

MEASURE THIS DISTANCE

DR

TRACK

1000

0945

0900

x

x

x

The second method for finding the speed or DRIFT is a calculation using DSTreet.

DR

TRACK

0945

0900

x

x

x

The second method for finding the speed or DRIFT is a calculation using DSTreet.

It is important to remember that each leg of the triangle represents what happened in the same ELAPSED TIME!

DR

TRACK

0945

0900

x

x

x

The second method for finding the speed or DRIFT is a calculation using DSTreet.

In this solution the BLUE line represents the CURRENT

DR

TRACK

0945

0900

x

x

x

The second method for finding the speed or DRIFT is a calculation using DSTreet.

In this solution the BLUE line represents the CURRENT

Measure the distance between the point on the DR-Line and the FIX position.

MEASURE THIS DISTANCE

DR

TRACK

0945

0900

x

x

x

The second method for finding the speed or DRIFT is a calculation using DSTreet.

In this solution the BLUE line represents the CURRENT

Measure the distance between the point on the DR-Line and the FIX position.

In our DSTreet;

D = this distance

T = ELAPSED TIME (0.75 in this problem)

MEASURE THIS DISTANCE

DR

TRACK

0945

0900

x

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