Edited by Rachel Duncan 4th Edition ISBN 0-907649-91-2 London ...

Navigation 61
Along with your sextant you need a current Nautical Almanac and Sight Reduction
Tables for your latitude. For land, use an artificial horizon (mirror or oil/mercury bath
system) and a reliable watch. It will also require some homework and practice. However,
great satisfaction and a feeling of pioneering can be obtained by crossing a wilderness and
reaching your desired destination by simple astronomical observations and arithmetic.
For ease of calculation and elimination of the Reduction Tables, there are pocket
calculators programmed to do the work for you, e.g. the Merlin II or the 'IS’ tables, which
although very simple, require extreme care in transposing figures and eliminates the
Reduction Tables. Here you carry out mathematically what the calculator would do and it
requires just a few sheets of tables.
6.6 Local knowledge
The Arctic writer Barry Lopez noted in his book Arctic Dreams that the Eskimos/Inuit,
without ever seeing a map, could draw remarkably accurate sketches of coast lines and
would detail features probably irrelevant to the mapmakers. Even in the Antarctic, there
are now few areas which that have not been travelled. Ask around for information.
However, use advice given in conjunction with your other navigational aids.
Amongst the islands of the Arctic there are still numerous communities. Some will
be hunters and traders and may be able to pass on information on local topography, ice
conditions, and weather that could be invaluable to your journey.
6.7 Finding your way
As with all navigation, practice, with meticulous records, keen observation and careful
interpretation are imperative.
• Before leaving, mark on the map your departure point and where you are going.
Make a written route plan. Work out bearings and study the map for topographical
features that may be relevant to pinpointing your position;
• An idea of your rate of travel will be invaluable to confident evaluation of distance
travelled. Record your travel times between known points and find variations for
different terrain. Walking for a given time on a specific course will put you within a
surprisingly accurate location at a given time;
• You may consider it worth fixing a wheel with a mile counter to your sledge.
Having steered an accurate compass course, knowing from the wheel odometer to
within one or two percent your distance, your position can be assured!
• By keeping a detailed account with known or assumed positions, directions
travelled, times, etc., there is always a reference to help when confusion arises.
Return to basics and study the records. Somewhere there will be a clue that will
clarify doubts;
• Perhaps a feature appears where there is none on the map. First check your line of
travel on the map. Is it correct? Then what about the distance from your last known
point? Is your compass bearing correctly transferred onto your compass and, are
you reading it correctly? Is the sun in the correct position relative to your direction
of travel? Are there any other known landmarks that can confirm your position?
• Each aid in navigation – distance, bearing, time, sun, topography, map, when used
individually gives only part of the story. By interrelating all of these you could well