Navigation

Learning Objectives Explain the differences between pilotage and dead reckoning. List at least 7 items of equipment for diving navigation. List at least 6 aids to natural navigation. List at least 5 ways to measure distance underwater and state which is most accurate. Compare the following: heading, bearing, course, and fix. Describe variation and deviation and state the cause and effect of each. Explain how to circumnavigate an underwater obstacle. Contrast true north and magnetic north.

Main Points Methods of Navigation Measuring Distance Underwater Natural Navigation Fixing a position Compass Navigation

Methods of Navigation Pilotage –Confirming location using visual checkpoints Dead Reckoning –Estimating position based on distance and direction. –This system requires keeping track of speed, time, and direction of travel. Combination –Using one system to confirm the other

Measuring Distance Underwater Measured line/tape measure –most accurate Arm spans Kick cycles Air consumption Time

Natural Navigation Underwater landmarks –pick something permanent. Ripple Marks –parallel to the wave front –deeper/steeper ripples = waves feel bottom more –ripples closer together = waves closer together Surge –typically onto and off of shore –strongest toward shore Currents Bottom contours Sunlight or changes in light

Fixing Position Ranges –Establishes 1 line of position (LOP) Fixes –Use multiple lines of position to establish position

Compass Navigation Terminology –True North Geographic North pole –Magnetic North Point near the North Pole towards which a compass needle points. –Variation Local differences between True and Magnetic North. –Deviation Difference between Magnetic and Compass North. Caused by –Metal –Magnetic source

Compass Navigation cont. –Bearing Angular direction from an object expressed in degrees. Bearings may be expressed in terms of True, Magnetic, Compass or relative degrees. –Heading A course followed or to be followed –Leeway Sideways slipping due to wind or current.

Compass Navigation Cont. Uses of a compass –Follow a specified heading/direction/course –Establish bearing/direction to an object –Fix position

Compass Navigation Cont Parts of a compass –North seeking needle needle always points –Compass card card with course numbers always points north –Lubber line used to determine direction of travel –Sights –Index marks –Rotating Bezel –Navigators window allows you to read the course from the side of the compass Provides actual compass course

Compass Navigation Cont Siting a course –best way is to site across the compass –alternatively align lubber line with center of diver and desired course.

Compass Navigation Continued Patterns –Straight line/reciprocal –Squares/Rectangles –Triangles –Circumnavigating 90° turns Constant distance

Compass Navigation Cont Common Errors –Not paying attention –Compass not level –Not believing the compass and following your nose –Compass pointed in the wrong direction –Not keeping track of distance

Compass Navigation Cont. Miscellaneous Equipment –Slates –Markers –Floats –Compass board –Charts

Main Points Methods of Navigation Measuring Distance Underwater Natural Navigation Fixing a position Compass Navigation

Learning Objectives Explain the differences between pilotage and dead reckoning. List at least 7 items of equipment for diving navigation. List at least 6 aids to natural navigation. List at least 5 ways to measure distance underwater and state which is most accurate. Compare the following: heading, bearing, course, and fix. Describe variation and deviation and state the cause and effect of each. Explain how to circumnavigate an underwater obstacle. Contrast true north and magnetic north.