Checking It

With GPS we happily rely on a single source of information. Without GPS, the rule is that a solitary source will not provide a trustworthy answer. Different sources should tell the same story even if they tell it at different times and in their own way. The first sign of


approaching land could be when you pick up long wave radio programmes. Later when you start receiving Fm programmes you could begin looking for clouds building up over an island or along the coast. Soon you would expect to see seabirds, perhaps shipping lanes, aircraft losing height for landing, changes in the swell, flotsam both natural and man-made and finally the appearance of inshore traffic and local fishermen.

The Crash Bag Navigator snaps up every snippet of information and uses them as pieces of a jigsaw that shows the world around the boat, and its place in it. This is an ever-changing picture, modified whenever any new piece of information comes to hand. Keeping this plot up to date is a full-time job. The electronic navigator knows only what his screens tell him. His position is a dot or a series of figures on a screen. It is not something he knows or something that he has worked out and can prove. It is something he is told and must unquestioningly accept. Deprived of his solitary source of information an electronic navigator stops navigating. A Crash Bag Navigator who loses one source of information carries on. His supply of information has diminished, not dried up. He may be uncertain of his position but he is never lost.


Acrux öS Aircraft 17ö/184 Almanacs 13/178 Altair, Summer Triangle ö3 Altitude 13/57-114/122et seq/

13ö et seq Altitude Difference Method 3 Altitude Local Noon By Equal Altitudes 81 Amplitude 39/44/46 fig/47/48 Analemmatic Sundial 50 Apparent Magnitude 63/69 Defintion A Star To Steer By 65/67 Astrolabe 3/13/114/116/128 Azimuth 57 Azores 28

Back Staff 124

Bede, The Venerable 11

Betelgeuse 71

Big Dipper 59 fig/61/83

Birds 12/34/50/184 Birds Flight Paths 11 Board Of Longitude 147 Bow And Beam Bearing 108

Cape Guardafu 11 Cape Verde Isles 11 Captain John Campbell RN 147 Cassiopeia 138 Cassiopeia, North From 60 Cassiopeia, Time From 83 Celestial Coordinates 54 Celestial Navigation 4/6/90/183 Capt Thomas H Sumner 3 Celestial Sphere 54/55 fig /69 Chart Portolan 36 Chih 114 Chinese 13

Circle Of Error 24/180/181 fig/182 fig Circumpolar Stars 71/141 Circumpolar Stars, Latitude From 139

Clearing Distance By Similar Triangles

Diffraction 170


Dip 107/128/130/136

Clouds 146-175/178

Dip Magnetic 146

Columbus 11/90

Dipping Distance 100/101 fig

Compass 2/4/12/13/18/25

Distance Off By Bearings 107

Alexander Neckham 13

Distance Off By Echo Ranging 109

Compass Card 39

Distance Off By Horizon Angle 107/

Compass Card 39

108 fig

Compass Making 36et seq

Distance Off By Horizontal Angle

Compass Points 36/39/51

104/105 fig

Compass Rose 36/39/97

Distance Off By Similar Triangles

Compass, Star 70

102/103 fig

Compass, Sun 50et seq/51 fig

Distance Off By Vertical Angle

Compass, Local Noon 80


Cook, James 147

Distance Off By Winking 105

Coriolis Effect 97

Distance To Sail 155

Corrections For Polaris 138

Distance To Your Horizon 100

Course Errors 180

Doubling The Angle On The Bow

Course To Steer 152/154 fig

42/107/108/110 fig

Cross Staff 122 FIG/123/124/

Dead Reackoning 90


Dutch Shoe 124

Currents 95 et seq/168

Dutchman's Log 90/92

Cygnus 63


Edward Wright 162

David Lewis 12

Equation Of Time 79/80 table

Davis, John 2/124

Estimated Position 90/95/96 fig

Dead Reckoning 6/90 et seq

Eudoxus Of Cyzicus 11

Declination 44/47/48/51/56 fig/




Flamsteed, John 146

Deliberate Error 30

First Point Of Aires 56/57/60


Gerardus Mercator 162 Greenwich Hour Angles 56 Greenwich Meridian 56/78

Half Latitude Rule 69 Hanno 10 Herodotus 10 Homemade Charts 162 Homemade Logs 3/90 et seq Horizon Sight 129

Kamal 117/119 fig

Landfall 12/24 et seq/90/176 Landmark Navigation 16/17fig Latitude 11/26/44/47/51/54/ 69/82/83/115/121/ 126/132/134/148/152/183 Latitude By Polaris 59/138 Latitude Hook 117 Latitude Scale 162 Leadline 3/10/13 Leeway 90/97/181 Local Noon 36/44/80/81/148 Local Noon By Equal Altitudes 81 Lodestone 13

Log Ship 3/92/93 fig/94

Longitude 26/57/78/79/ 145 et seq/152/162 Longitude By Time 148 Longitude Scale 162

Making A Magnetic Compass 36 et seq Making A Sundial 82et seq Map Navigators 17 Marine Astrolabes 114 Marc St Hilaire, Admiral 3 Martin Creamer 12 Measure Angles, Hands And Fingers 114

Measure Angles, Sextant 147 Mental Maps 14/19/21 Meridian Passage 44 Meridian Sight 132 et seq Meridian Stars 65 Midday Sun 17 Minoans 10 Mintaka 63

Moon, Lunar Distances 146

Moon, Lunar Eclipses 146

76 fig/120/130 Moon, Time From 85

Nautical Almanac 130/147 Navigational Calculators 2 Neckham, Alexander 13

Nocturnal 25/84 et seq North By Your Watch 48 North From Cassiopeia 60 North From Pegasus 61 North From Polaris 59

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