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.

Fl 8s 42 ft 8M beacon on Duttons Island. 41Â° 44.0' N, 071Â° 44.2' W

G â7â Fl G 4s 41Â° 37.4' N, 071Â° 50.0' W

G C â1â at the entrance to Blackfish Creek 41Â° 34.6' N, 071Â° 53.8' W

G C â3â within the Creek. 41Â° 33.9' N, 071Â° 54.4' W

G â5â Fl G 4s GONG 41Â° 38.6' N, 071Â° 46.4' W

G â3â Q G 41Â° 39.4' N, 071Â° 39.4' 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

At the end of Part 2, your vessel is south of Channel Island.Â You have just taken a fix at 1316, and your position is L 41Â°Â 39.2â N, LoÂ 071Â°Â 53.5â W.

âMeasure theÂ true course to the beacon, then determine magnetic course.Â Label course line with theÂ magnetic heading.

T = 055Â° Â

V = 015 W

C = 070Â° M

Plot and label the Course, C 070 M, above the course line, and your speed below the course line, S 25.0.Â Speed is to nearest tenth of knot.Â

You can measure the distance of this leg with your dividers and the latitude scale.Â The distance to the 18' sounding line is 7.2 nm.

Determine ETA by calculating how long it will take to travel 7.2 nm.Â Use the starting time of your fix, 1316.

Â D = 7.2

Â 60 D = ST

Â 60 * 7.2 / 25.0 = T

Â 17.28 min = T

rounding to nearest minute, 17 min.Â Add 17 minutes to the time you started the leg.

The ETA becomes

Â Â 1316

Â Â __+ 0017__

Â Â 1333

Measure latitude and longitude with your dividers

For question 9c, I plotted the bearing of the vessel at 1323 and 1325.Â To do this, I first calculated the 1323 DR, and the 1325 DR.Â Then, I drew a bearing line representing the bearing at 1323, and another at 1325.Â I used a dashed line for the bearings, since these were not my vessel's course, nor were they bearings used to develop a "fix."Â Â Â

1323 DR:Â Â Â Â Â Â Â Â Â Â 1325 DR:

Â 1323Â Â Â Â Â Â Â Â Â Â Â Â 1325

Â Â 0007 minÂ Â Â Â Â Â Â Â 0009 min

Distance traveled:

Â Â 60 D = STÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â 60 D = ST

Â Â D =Â __25 * 7__Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â __D = 25 * 9__

Â Â Â Â Â Â 60Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 60

Â Â D = 2.92 rounds to 2.9Â Â Â Â Â D = 3.75 rounds to 3.8

Since each sighting of the boat is at a relative bearing, we must convert to True bearing before we can plot on our chart.Â Then, in order to label each bearing, you must calculate the magnetic bearing.Â Remember, you measured your course to the Duttons Island light as 055 True:

TB = RB + THÂ Â Â Â Â Â Â Â Â Â Â Â Â TB = RB + TH

TB = 340Â° +Â 055Â°Â Â Â Â Â Â Â Â Â Â Â TB = 025Â° + 055Â°

TB = 035Â°Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â TB = 080Â°

Then, convert to magnetic bearing, and label the two bearings

T = 035Â° Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â T = 080Â°

V =Â 015 WÂ Â Â Â Â Â Â Â Â V = 015 W

M = 050Â°Â Â Â Â Â Â Â Â Â Â M = 095Â°

These bearings are plotted with time above the dashed line and the bearing below.

Question 9c asks, "Most likely what is your course of action andÂ why?"Â In the Marine Navigation Student Guide, Ch 6, paragraph 42-43 (page 85), the text mentions the use of relative bearings to determine whether you are on a collision course with another vessel.Â Â

If the relative bearing between your vessel and another vessel does not change, you are on a collision course with that vessel.

If you look at the position of the second vessel at both times, it appears that the second vessel has already passed in front of your vessel.

Plot your GPS position at 1335.Â Label this as a fix, "1335 GPS".Â Â

T = 223Â°

V = 015 W

M =Â 238Â°

You want to monitor any Cross Track (XTE) error to avoid the rocks near G â5â Fl G 4s GONG. YouÂ want to leave a margin of at least 0.4 nm.

As shown in Figure 3 and figure 4 of "Plotting and Labeling Standard," use a dashed line to represent the XTE and label "XTE D 0.4" for a distance of 0.4 nm.Â Note in this case you could have set XTE at approximately 1.0 nm before coming close to the rocks.

11. c What information should the GPS provide for your navigation after you have entered

Name of each WP, bearing to next WP, distance to next WP, cumulative

12.aÂ Â As you approach G â7â Fl G 4s the GPS indicates a distance of 8.1 nm and a bearing of 092Â°Â MÂ **to the next waypoint in the route. You know the distance should be 3.9 nm and the bearing shouldÂ be 240Â°****Â M.Â What did you do wrong?**

In this case, I plotted the course C 091 MÂ and distance of 8.1 nm.Â I used a dashed line to indicate this was a construction line.Â You need to convert to true to plot this lineÂ

T = 077

V = 015 W

M = 092

When you plot this course and distance, you see it is the course and distance to G "3" QG, located at LÂ 41Â° 39.4' N, Lo 071Â° 39.4' W.Â You have entered the wrong waypoint in your GPS route.

12 b.Â Â What three items of information will the GPS give you when you press ânearest waypointâÂ on the menu screen as you pass by R â6â Fl R 4s on your starboard beam?

Assume that you are passing at a SB beam bearing, ie, RB = 090Â°.Â Your course is 238Â° M.

Your GPS is setup so that it reads magnetic bearings, so your calculnn all be in "magnetic".

MB = RB + MH

MB = 090Â°Â + 238Â°

MB = 328Â°