illustration-Alex Zidock Jr. Magnetic North Magnetic South graphic-National Oceanic and Atmospheric Administration This compass rose depicts true north with a star at "0" degrees. Also note that magnetic north is shown as "0" degrees but with an arrow. In the center of the rose, it shows that the variation between true north and magnetic north is 12˚ west. or parallel to it. It is the matching of the lubbers line to the markings on the compass rose that indicates the direction the boat is traveling as related to the earth's magnetic north. When north is not north Iron affects compasses Magnetic variation is the difference between the earth's geographic north and the earth's magnetic north. The geographic or "true" north is at the North Pole where lies the actual axis of the earth's rotation. The earth's magnetic north is near but not at the same place. The difference in these locations is called "magnetic declination." To add to this mix of deciphering "north," the magnetic declination can vary at different places around the globe. In fact, before this was understood, when Columbus was making his first voyage across the Atlantic Ocean in 1492 the variations in his magnetic compass were so erratic that he kept the information from his crew as not to frighten them. Magnetic compasses must also be corrected for deviation caused by surrounding iron or iron containing materials. Once a magnetic compass is mounted it should be calibrated. Follow the instructions that come with the compass. Compasses and charts illustration-Alex Zidock Jr. Magnetic North COURSE HEADING 270 DEGREES WEST COURSE HEADING 90 DEGREES EAST COURSE HEADING 0 DEGREES NORTH PFBC website: www.fishandboat.com Scientists believe that the Earth's core is made of molten iron that creates a magnetic field around the earth. Magnetic objects' opposites attract. There is a difference in magnetic north and the north/south axis on which the earth rotates. This is called the variation and is measured in degrees when navigating with a magnetic compass. Nautical charts also contain a compass rose. This rose is basically an outer circle that shows true north and an inner circle that shows magnetic north at the particular location the map depicts. Each has 360 graduations but is offset as determined by location and magnetic variations. The boater must be able to convert back and forth between true and magnetic headings to reach a given destination. In smaller boats where directional electronics are impractical and on smaller bodies of water, a magnetic compass can be invaluable when finding fishing spots or finding your way back to the launch ramp when night or fog hamper visibility. As a low cost backup to electronics on larger vessels, adding a good magnetic compass is prudent. Magnetic north is shown as 0-degrees on the dial of a compass. Pennsylvania Angler & Boater * January/February 2015 39http://www.fishandboat.com