Â **Marine Navigation Cruise**

Finding the answers to the cruise is like solving a puzzle.Â You piece together the "clues" and determine your course and position, plotting on the chart.

Part of the challenge of the cruise is knowing where to start. Here is a list of the lat/lon positions of key locations in part 1 of the cruise. Latitude is in degrees N, longitude is degrees W. If you see any errors below, please let me know.

G C â5â Â Â Â Â Â Â Â Â Â Â Â Â Â 41Â° 33.9' N, 072Â° 05.5' W

R â4â Q R Â Â Â Â Â Â Â Â Â Â Â Â Â 41Â° 36.1' N, 072Â° 04.8' W

G â3â Q G Â Â Â Â Â Â Â Â Â 41Â° 35.7' N, 072Â° 04.1' W

Qk Fl 20 ft Â Â Â Â Â Â Â Â Â 41Â° 34.9' N, 072Â° 07.2' W

E Int 6s 40 ft Â Â Â Â Â Â Â Â Â 41Â° 34.5' N, 072Â° 08.6' W

R â2â Fl R 4s Â Â Â Â Â Â Â Â Â 41Â° 37.3' N, 072Â° 01.5' W

G â1â Fl G 2s. Â Â Â Â Â Â Â Â Â 41Â° 36.7' N, 072Â° 01.0' W

RW âORâ Mo (A). Â Â Â Â 41Â° 37.5 ' N, 071Â° 59.7' W

Tower R Lt on the hill to the north,Â Â Â Â Â Â Â Â Â 41Â° 45.6' N, 071Â° 55.2' W

Chapman Point light Fl 6s 18M HORN. Â Â Â Â Â Â Â Â 41Â° 41.4' N, 072Â° 05.5' W

R â10â Q R Â Â Â Â Â Â Â Â 41Â° 39.6' N, 071Â° 57.6' W

The cruise is found in Appendix A, p 97 of the Student Manual.

The cruise is taken on Bowditch Bay.Â For all questions, use a variation of 15 W

Refer to the chart below.Â Starting point for the cruise is on the lower left hand corner of the Bowditch Bay chart.

1.Â You plan to leave G C â5â buoy, on a course for mid channel between R â4â Q R and G â3â Q G.Â Measure Course with Course Plotter and Distance with dividers.Â Plot this leg of the cruise.

You leave your starting point, G C "5", at 0600.Â This gives you a fix - the buoy and the time.Â Label the fix, a circle, with the time, parallel to the bottom of the chart.

Determine your true course, then magnetic course.Â Label course line with the magnetic heading.

You can measure the distance of this leg with your dividers and the latitude scale.

T = 023Â° Â

V = 015 W

C = 038Â° M

D = 2.2

Â Â Â Â 0600

Â Â Â __+Â 0026__

Â Â Â Â Â Â Â 0626

When a change is made to the course, or speed of the vessel, you plot the DR.Â The symbol for a DR is a semicircle, with a dot at the center.Â The time of the DR is labeled at an angel to the bottom of the chart - usually around 45Â°.

Â **1e.**Â New Course is Reciprocal of the range:

True Range = 245Â°

ReciprocalÂ Â Â __- 180Â°__

Â Â Â Â Â Â Â Â TÂ Â Â 065Â°

Â Â Â Â Â Â Â Â VÂ Â Â __015__Â W

1f. Determine ETA mid channel between R â2â Fl R 4s and G â1â Fl G 2s.Â

You can draw a "construction line" (dotted line) between R â2â Fl R 4s and G â1â Fl G 2s. Measure the distance from your 0626 DR.

Determine the time to travel that distance, then add it to your 0626 time.

Â D = 2.6

Â 60 D = ST

Â 60 * 2.6 / 5.0 = T

Â 31.2 = T

Â Â Â 0626

Â Â __+ 0031__

Â Â Â 0657

Time to 0700 DR is 0700 - 0657 = 3 minutesÂ

Â 60 D = STÂ

Â D = 5.0 * 3 / 60

Â D = .25 round to nearest tenth = 0.3

Plot the 0700 DR on the course line

Measure the L/Lo to be:

Refer to chart below.

2.Â From 0713 Fix.Â Change course toÂ 031Â° T.

T = 031Â° Â

V = 015 W

C = 046Â° M

2b.Â ETA at R"10"QR:Â (seaman's eye - R"10" QR is abeam)

Draw a construction line perpendicular to your course line throughÂ R"10"QR.Â Measure distance from 0713 fix.

Â D = 2.6

Â 60 D = ST

Â 60 * 2.6 / 10.0 = T

Â 15.6 = T

Â Â 0713

Â Â __+ 0016__

Â Â 0729

2.cÂ Measure distance from 0713 fix to 8' sounding

D = 4.8

60 D = ST

60 * 4.8 / 10.0 = T

28.8Â = T

Â Â 0713

Â Â 0742

3.Â Refer to chart below.Â For clarity, only the 0742 bearings and fix are shown.Â Also for clarity, the label for the 0742 fix is a short distance away from the fix, with an arrow to the fix symbol (circle).Â The label "0742"Â is parallel to the edge of the chart

At 0742, you take bearings onÂ Tower R Lt on the hill to the north, andÂ Chapman Point light Fl 6s 18M HORN, with hand bearing compass, to plot a fix.Â Remember that the magnetic bearings must be converted to true before plotting.

TowerÂ Â Â Â Â Â Â Â Chapman

T = 012Â°Â Â Â Â Â Â Â Â T =Â 267Â°

V = 015 WÂ Â Â Â Â Â Â V =Â 015Â° W

C = 027Â° MÂ Â Â Â Â Â M = 282Â°

Plot and label each bearing.Â The intersection of these two bearings is a fix.Â Plot and label the 0742 fix.