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Navigation and Bathymetry

Navigation and Bathymetry. Why is it important for you to be able to read maps and navigate? What’s wrong with GPS? Rely heavily on power and satellites Salt water and batteries Sun spot activity breaks down radio transmissions Always good to know how to use a map and compass.

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Navigation and Bathymetry

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  1. Navigation and Bathymetry

  2. Why is it important for you to be able to read maps and navigate? • What’s wrong with GPS? • Rely heavily on power and satellites • Salt water and batteries • Sun spot activity breaks down radio transmissions • Always good to know how to use a map and compass

  3. Finding locations on maps • On graphs, there are X and Y coordinates • Need to adapt these coordinates for a spherical world • Lat and Long

  4. Latitude- parallels, 0-90 °N&S of the equator (always put the letter); always the same distance between each latitude line • Longitude- meridian, meet at the poles so always different distances between the longitude lines, 0-180°E&W • Writing: degrees(°), minutes(‘), seconds(“) Conway= 35° 50’ 9” N, 79° 2’ 53” W

  5. On the charts • Lat and long do not have letters, why? • Its on a small scale, you should know where you are • What hemispheres are we in? • Lines are straight, why? • Small scale

  6. 30’ 20’

  7. Speed and Distance • Subtraction: 60 sec=1 min, 60 min=1 deg • So you’re subtracting time 5 82 36° 22’ -34° 42’ 1° 40’ 1’ of latitude=1 nautical mile= 1.15 statute (land miles) Why latitude?? • Speed is measured in knots (1 nautical mile per hour) --a line with knots on it • 30’ latitude in 1 hour = 30 knots

  8. Plotting courses • Read the course headings as 0-360°, not NSEW letters • Geographic North Pole- ‘true’ north, the top point of earth where you normally think of the north pole • Magnetic North Pole- magnetism of the Earth, moves around and sometimes flips to the geographic south pole • Therefore we need to make corrections, because our compasses point to the magnetic north pole, not geographic north

  9. Bathymetry • Study of the depths, ocean floor • Old days- drop a lead-line and determine how much rope was let out, then measured it in arm lengths, or FATHOMS • 1 fathom=6 feet, 3feet=1 meter • Current way- sonar or echosounding • Sound has a speed of 1500m/s in water

  10. Soundings- the depths at particular points, these are shown on the charts as single numbers • Contour lines- lines that connect equal depths (5fm, 10fm, 100fm, 1000fm) • Bathymetric profile- an X-Y graph of depth versus distance

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