Compass Sea School Ltd

Ocean sailing is, however about more than just using a sextant. Another important aspect of ocean sailing is worldwide meteorology, passage planning and communications at sea. Publications that assist the ocean navigator such as routeing charts and other pilot books will be discussed. The course also recognises that there has been a vast improvement in technology available to help with ocean routeing and weather prediction. Time will be spent discussing the various computer programmes, internet sites and satellite/radio broadcasts available to the modern ocean navigator. Crew management, watch keeping, victualling, water and fuel management and emergency equipment are also covered.

The earth and the celestial sphere

• Definition of observer’s zenith and position of a heavenly body in terms of latitude, longitude, GHA and declination
• Right angle relationships, latitude and co-lat, declination and polar distance
• Relationship between GHA, longitude and LHA
• Tabulation of declination in nautical almanac
• Rate of increase of hour angle with time

The PZX triangle

• The tabulated components of the triangle, LHA, co-lat and polar distance
• The calculable components, zenith distance and azimuth
• Relationship between zenith distance and altitude
• Introduction to the tabular method of solution in the Air Navigation Tables and the basic sight form
• The use of calculators for the solution of the PZX triangle

The sextant

• Practical guide to the use and care of a sextant at sea
• Conversion of sextant altitude to true altitude
• Application of dip, index error and refraction
• Correction of side error, perpendicularity, index error and collimation error

Measurement of time

• Definition of, and relationship between, UT, LMT, standard time and zone time
• Rating of chronometers and watches

Meridian altitudes

• Forecasting time of meridian altitude
• Reduction of meridian altitude sights

Sun, star and other sights

• Reduction and plotting of sun sights using
• Air Navigation Tables
• Awareness of use of calculator for sight reduction
• The plotting of sun-run-sun meridian altitude
• Awareness of the reduction and plotting of sights obtained from stars, moon and planets

Compass checking

• Use of amplitude and azimuth tables systems and/or calculator

Satellite Navigation Systems

• Principles and limitations of use of all systems

Great circle sailing

• Comparison of rhumb lines and great circles
• Vertices and composite tracks
• The computation of a series of rhumb lines approximating to a great circle by use of gnomonic and Mercator projections

Meteorology

• General pressure distribution and prevailing winds over the oceans of the world
• Tropical revolving storms, seasonal occurrence and forecasting by observation

Passage planning

• Publications available to assist with planning of long passages (routeing charts, ocean passages of the world and other publications)
• Preparation for ocean passage including survival equipment, victualling, water and fuel management, chafe protection, spares and maintenance

Passage making

• Navigational routine
• Watchkeeping
• Crew management

Communications

• Satellite and terrestrial systems
• Weather information