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Proper use of a compass on the water.

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  • Proper use of a compass on the water.

    I am trying to learn to use a compass properly on the water and no one yet has been able to explain it in layman's terms, either that or all the guys I know with compasses haven't a clue what they are looking at . AllDodge recently said on a post talking about repairing a compass that " I am on a lake and there is no need for it" I have asked him what he means by that. I have a bit of an answer myself but need to know what the difference is using one on land vs. the water. I'm thinking for simplicity if I head out of a marina and it reads 0 degrees South I need to make a heading to 180 degrees North to get back. Depending on what my location is I can hit a shoreline or island way before I hit 180 North.

    I am on the north shore of Lake Erie. We got into the worse fog I have ever seen a few years back, I'm talking stew not soup. The Marina operator had to go out and bring in a boat. No idea how he found him to this day. Worse he ever saw in 50 years on Erie. Had I not had my GPS we could have ended up on the rocks. I have since bought a battery booster for that specific incident. If not for the GPS I don't know what I would have done. It was unnerving to say the least, almost scared and I don't scare (ha). Take a North heading and crash on the 5 mile wide shoreline of rock or head south east into open water and listen for lake freighters. I have been far too close to one of those things and actually was responsible for docking them at the Steel Plant. They will run you over and not know it. Especially in a glass boat.
    Experience is a lifetime of mistakes, wisdom is not making them again.

  • #2
    First of all, 0 degrees is north . . . 180 degrees is south. 90 is east . . . 270 is west.

    Keep in mind that the compass is reading magnetic north, not true north (north pole) so you have to use a navigational chart to see what the difference is between the 2 north points in your area. (called the 'compass rose' on the chart)

    So, you really need the compass and the chart to find your way in fog or when you cannot see the destination or even a waypoint along the way.

    Not too long ago, before I had a GPS on my boat, I used the chart to figure out where I was versus where I wanted to go. and then checked what the compass heading would be according to the chart. As you travel to familiar places, you will tend to know the compass heading and just naturally steer the boat accordingly. An example is that from my Harbor, if I want to head towards Woods Hole, I take a heading of 210 once passing the outer buoy of the harbor. That gets me headed towards Wood Hole, and as I get near buoys and landmarks associated with that area, I can make adjustments to my course and then plan the next compass heading, etc.

    Not sure if all that helps, but feel free to ask more questions.

    To your other point, smaller bodies of water are not as 'compass dependent' because you can see land and eventually will reach shore without getting too lost. As you navigate large bodies of water (great lakes, bays, oceans, etc) the seeing part gets diminished and that is where the compass comes in.
    Last edited by tpenfield; July 15th, 2017, 06:06 AM.
    Best regards, Ted . . . . Cape Cod, MA

    Formula 330 Sun Sport, O'Day Mariner Sail #3224, Sunfish
    Past Boats: Catalina 22 Sail #10531, Formula 242 Sun Sport
    Twin Mercruiser 7.4 LX MPI (0F802036, 039), Bravo 3's (0F806198, 199), Mercury 7.5 HP (1969), Johnson 4.5 HP (1980)

    My Boating Web Pages: http://www.tpenfield.com

    Member of the Month - February 2013

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    • #3
      Compass works the same on land or water. There's usually a bigger compass on the boat than what you would use for "orienteering" because you want better accuracy when your life really depends on not making a 0.5 deg error.

      Comment


      • #4
        Originally posted by tpenfield View Post
        First of all, 0 degrees is north . . . 180 degrees is south. 90 is east . . . 270 is west.

        .
        Proved my point. And it does help. To properly use a compass on the water it must be used in conjunction with a navigational chart, electronic or paper. You would chart a course in increments using the compass to verify your heading. Is that about right? That's why you see the Capt etc. using a straight ruler charting and marking the course on the chart.

        I wrote on my OP.
        "The Marina operator had to go out and bring in a boat. No idea how he found him to this day. Worse he ever saw in 50 years on Erie" He either had a GPS reading and charted a course for it or had Radar on his boat.
        Last edited by Old Ironmaker; July 17th, 2017, 01:40 AM.
        Experience is a lifetime of mistakes, wisdom is not making them again.

        Comment


        • #5
          "I am trying to learn to use a compass properly on the water and no one yet has been able to explain it in layman's terms..."
          I don't understand the difficulty you're having - it's a pretty simple device and just takes a bit of practice.
          North is always north and the compass tells you your heading with respect to that. That's it, no mystery.

          If you're familiar with your area, you can get by with just a compass.
          I run a water taxi out of a marina and practice has made me memorize the bearings to our waypoints (markers, reefs, etc). The plotter is always on and so is the radar in low vis but, if they went down, it wouldn't affect our ability to put passengers safely onto the dock.

          One point that hasn't been mentioned: you need to prove (swing) your compass periodically to check its accuracy. Plot a bearing on the chart, then follow it on the water. After allowing for declination, if there's a difference between the two bearings you need to compensate your compass, either with magnets or a compass card.
          Google "swinging a compass" - it's a pretty simple process. Just like everything else on the boat, the compass takes a bit of maintenance too.

          "...when your life really depends on not making a 0.5 deg error."
          If a .5 degree error is life threatening, you need to fire your navigator for putting you so close to a hazard, then for not confirming your position periodically

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          • #6
            Originally posted by Chigwalla View Post
            "...when your life really depends on not making a 0.5 deg error."
            If a .5 degree error is life threatening, you need to fire your navigator for putting you so close to a hazard, then for not confirming your position periodically
            Exactly! A 0.5 degree error over 10 miles is only around 500 feet. I would love to be within 0.5 degree over 10 miles. Apparently said by someone who has never navigated by a compass over long distances.

            Before GPS, I would navigate out to an island off southern California where is started out foggy so you didn't see the island until you got within a mile of it. Used charts, compass and parallel bars typically. I started a stop watch and calculated my speed and time to make sure I didn't blow by it.

            I learned navigating, when I was a little kid, in a Coast Guard Auxiliary class. Do they still do those?

            I use a compass all the time on Lake Tahoe even with a GPS when I am going over 10 miles. I plug in the waypoint and get the value of my course. When I steer, I pretty much just look at the compass to match my heading to the course. That way I am not staring at the GPS all the time. I guess I am old school because that's what I did when I used to fly.
            Last edited by bruceb58; July 17th, 2017, 10:09 AM.
            1998 Wellcraft Eclipse 24 Cuddy
            Volvo Penta Duo-Prop 7.4L "LK"

            2006 Sun Tracker Party Barge 21
            Mercury 90 4-Stroke FI
            "Common sense is not very common"
            "Failing to prepare is preparing to fail." -- John Wooden

            Comment


            • #7
              Originally posted by Chigwalla View Post
              "I am trying to learn to use a compass properly on the water and no one yet has been able to explain it in layman's terms..."
              I don't understand the difficulty you're having - it's a pretty simple device and just takes a bit of practice.
              North is always north and the compass tells you your heading with respect to that. That's it, no mystery.

              If you're familiar with your area, you can get by with just a compass.
              I run a water taxi out of a marina and practice has made me memorize the bearings to our waypoints (markers, reefs, etc). The plotter is always on and so is the radar in low vis but, if they went down, it wouldn't affect our ability to put passengers safely onto the dock.

              One point that hasn't been mentioned: you need to prove (swing) your compass periodically to check its accuracy. Plot a bearing on the chart, then follow it on the water. After allowing for declination, if there's a difference between the two bearings you need to compensate your compass, either with magnets or a compass card.
              Google "swinging a compass" - it's a pretty simple process. Just like everything else on the boat, the compass takes a bit of maintenance too.

              "...when your life really depends on not making a 0.5 deg error."
              If a .5 degree error is life threatening, you need to fire your navigator for putting you so close to a hazard, then for not confirming your position periodically
              If there is a 25 mile point like Long Point in Lake Erie a heading to me is useless if I get on the other side of the point from my harbour and I only have a compass. I will hit the point if I just follow the compass will I not? You say all I need is a compass but then mention charts, bearings, waypoints, declination, compensation, calibrations. More than "just a compass". Erie and Ontario can be like an ocean with zero landmarks. I always depend on the compass to maintain course rather than staring at the GPS. Without landmarks I find it more accurate since my split screen is small and want to see the sonar fishing. I didn't get my own real boat bigger than 14' until I was 55.

              Thanks for the info, lots to learn when you don't know.
              Last edited by Old Ironmaker; August 2nd, 2017, 04:29 AM.
              Experience is a lifetime of mistakes, wisdom is not making them again.

              Comment


              • #8
                A compass heading will get you headed in a general direction, but nothing that you can make a precise determination. Remember wind and currents (if any) will effect the true direction of travel, where as the compass will only show the direction the boat is pointed.

                Along the way, you will need to use landmarks, buoys and the chart to frequently determine your true position and then make any adjustments from there. If you are going only 5-10 miles, you can usually just head in the proper direction using landmarks or a compass heading.
                Best regards, Ted . . . . Cape Cod, MA

                Formula 330 Sun Sport, O'Day Mariner Sail #3224, Sunfish
                Past Boats: Catalina 22 Sail #10531, Formula 242 Sun Sport
                Twin Mercruiser 7.4 LX MPI (0F802036, 039), Bravo 3's (0F806198, 199), Mercury 7.5 HP (1969), Johnson 4.5 HP (1980)

                My Boating Web Pages: http://www.tpenfield.com

                Member of the Month - February 2013

                Comment


                • #9
                  Originally posted by Old Ironmaker View Post

                  If there is a 25 mile point like Long Point in Lake Erie a heading to me is useless...You say all I need is a compass...
                  Nope, that's not what I said.
                  Last edited by Chigwalla; August 2nd, 2017, 11:04 PM.

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                  • #10
                    0.5 deg error trying to go from SF to Hawaii will have you miss the islands completely

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                    • #11
                      there are 2 separate concepts - "variation" and "deviation". Variation was described above and is the diffference between true north and magnetic north for your area, at the time (magnetic north moves over time so old charts can be off). Deviation is how much error your compass will have based on ferromagnetic properties of your boat. If you need accurate bearings you'll need to work out a deviation table for your boat, as alluded to above.

                      Comment


                      • #12
                        Originally posted by fhhuber View Post
                        0.5 deg error trying to go from SF to Hawaii will have you miss the islands completely
                        Only around 20 mile error. Aim for the middle of the big island, that is 93 miles long, and you would be fine.
                        1998 Wellcraft Eclipse 24 Cuddy
                        Volvo Penta Duo-Prop 7.4L "LK"

                        2006 Sun Tracker Party Barge 21
                        Mercury 90 4-Stroke FI
                        "Common sense is not very common"
                        "Failing to prepare is preparing to fail." -- John Wooden

                        Comment


                        • #13
                          It makes navigation a thousand years ago even that more amazing. I can't image the courage of those sailors.
                          Experience is a lifetime of mistakes, wisdom is not making them again.

                          Comment


                          • #14
                            For navigation instruction, go to boatingcourses.ca

                            There will be classes near you that you can sign up for (maybe Boating 2 & 3).

                            Comment


                            • #15
                              Sign up today
                              I recommend the Power Squadron Piloting and Advanced Piloting Courses.

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