Introduction to Navigation Chapter 12 Introduction to Navigation

Lesson Objectives Selecting and keeping charts current Constructing and reading charts Use of navigation tools Select, adjust, mount, and correct a compass Plot a course and measure direction SSSpptChpt12Navigation040609.ppt

Lesson Objectives (2) Determine position by compass bearings Computing speed, time and distance Make a dead-reckoning plot Use of tide tables Electronic navigation SSSpptChpt12Navigation040609.ppt

Nautical Chart Features Projections-How to show round earth on flat surface Mercator Projection-a cylinder Distorts Northern latitudes Lat/Long scales are different Best for plotting over long distances SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Nautical Chart Features Projections Polyconic Projection- uses a cone Less distortion over small area Used in waterways such as AIWW SSSpptChpt12Navigation040609.ppt

Nautical Chart Features 5-C Chesapeake Bay 12282 1:25.000 5-B Chesapeake Bay 12263 1:80.000 5-A Chesapeake Bay 12280 1:200.000 Chart Scales What do all these numbers and symbols mean? SSSpptChpt12Navigation040609.ppt Reprinted with permission from How to Read a Nautical Chart by Nigel Calder

Nautical Chart Features Every chart has a: Title Block Type of projection Scale Vertical and horizontal datums Cautions and Notes Tide information References to other sources of information SSSpptChpt12Navigation040609.ppt Reprinted with permission from How to Read a Nautical Chart by Nigel Calder

SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Your Boat’s Compass Features Installation Adjusting SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Fixing Your Position Latitude-Angular degrees N or S of the Equator, measured 0-90 degrees Longitude-Angular distance E or W of Prime Meridian in Greenwich England, measured 0-180 degrees SSSpptChpt12Navigation040609.ppt

Fixing Your Position Parallels of latitude SSSpptChpt12Navigation040609.ppt

Fixing Your Position Longitude lines SSSpptChpt12Navigation040609.ppt

Fixing Your Position Locating a point on the chart using lat/long Be very careful reading the scales! SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Fixing Your Position Measuring distance There are 360 degrees of arc around the earth, so There are 22,600 minutes of arc around the earth 90 degrees X 60 minutes per degree = 5400 minutes 5400 X 4 = 22,600 minutes = 22,600 miles 22,600 nautical miles = circumference of the earth! 1 minute of arc equals 1 mile of distance And that’s why we use nautical miles at sea SSSpptChpt12Navigation040609.ppt

Fixing Your Position Plotting Courses Measuring direction We use a course plotter or: parallel rules aligned with compass rose SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Two Sources of Compass Error Variation Difference in degrees between true and magnetic north Deviation Compass error caused by nearby magnetic objects What is the local variation (see compass rose…) SSSpptChpt12Navigation040609.ppt

Correcting a Compass Reading True (T) + west Variation (V) - west Magnetic (M) - east Deviation (D) + east Compass (C) SSSpptChpt12Navigation040609.ppt

Finding Your Position Line of position-LOP FIX-where two or more LOPs cross Range LOP-Natural or manmade Bearing LOP-from compass Circle of position-from radar SSSpptChpt12Navigation040609.ppt

Finding Your Position Fix from two bearings to charted objects SSSpptChpt12Navigation040609.ppt

Finding Your Position Range LOPs SSSpptChpt12Navigation040609.ppt

Finding Your Position How to get compass bearings: Hand bearing compass Binocular compass Boat’s compass SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Speed – Time – Distance SSSpptChpt12Navigation040609.ppt

Dead Reckoning SSSpptChpt12Navigation040609.ppt

Tides Spring Tides-occur when moon and sun are aligned Neap Tides-occur when the moon and sun are at right angles relative to earth SSSpptChpt12Navigation040609.ppt

Types of Tides Diurnal Semi-diurnal Mixed SSSpptChpt12Navigation040609.ppt Reprinted with permission from the Weekend Navigator by Bob Sweet

Electronic Navigation GPS-Global Positioning System DGPS-Digital GPS-better WAAS-Wide Area Augmentation System-best Electronic Charts-2 types: Raster–“dumb” data—just pixels-a digital “photo” of a chart, all the data, all the time Smaller file sizes Vector–Smart data—each data type is encoded and layered Aids to navigation, topography, hydrography, etc. in separate layers Larger file sizes SSSpptChpt12Navigation040609.ppt

GPS/Chartplotters SSSpptChpt12Navigation040609.ppt Reprinted with permission from Using GPS: A Captain’s Quick Guide by Bob Sweet

http://nws.cgaux.org/index.html SSSpptChpt12Navigation040609.ppt