Survival Tips

SILVA 1 - 2 - 3 SYSTEM© (Applies to all compasses constructed in a similar way.)

1. Place compass on map with edge along desired line of travel. Make sure Direction of Travel arrow points towards your destination.

2. Rotate capsule until ”N” on graduation ring point towards North on the map. (Check compass housing North/South lines are parallel to map meridians.)

3. Hold compass horizontally in front of you. Turn yourself until red end of the needle points towards ”N” on the compass graduation ring. (Red end of needle will now be aligned to red North arrow in bottom of the compass capsule). Direction of Travel arrow now points precisely to your destination. Look up, sight on a land-mark and walk to it. Repeat this procedure until you reach your destination.

4. When using a sighting compass with a mirror, hold compass as per picture so that you can check direction by looking at compass housing in the mirror while sighting in correct direction of travel.

 Magnetic declination and how to compensate for it.

The difference, between Geographic North (North/South map meridians) and Magnetic North (towards which red end of the compass needle points), is called declination. The amount and direction of declination is shown on the map. For example: 20 degrees. For Easterly declination, adjust as follows:

With the declination scale inside the capsule (Field 7, Ranger 3 etc.) turn yourself until red end of the compass needle points to 20 degrees. on the ”E. declination.” scale – now the direction of travel arrow points in the correct direction.

With compasses that have a declination adjuster, you simply hold the graduation ring and turn the compass capsule until the red end of the North arrow points towards 20 degrees on the Eastern side of the declination scale. When this is done the compass will automatically adjust the bearing. Remember though, to use the North/South lines on the graduation ring as map North reference line when taking the bearing on the map.

• Always check the functionality of the compass before using it in the field.
  
• Never expose compasses to extreme temperatures (above + 60°C or below -40°C), or to magnetic fields such as knives, radio speakers, magnets, etc. Such exposure can cause permanent damage to them.
  
• With compasses that have a declination adjuster, (Voyager 9020, 8010 and 8040 etc) you simply hold the graduation ring and turn the compass capsule until the red end of the North arrow points towards 20 degrees on the Eastern side of the declination scale. When this is done the compass will automatically adjust the bearing. Remember though, to use the North/South lines on the graduation ring as map North reference lines when taking the bearing on the map.
  

Using an analogue watch

Why would anyone want to navigate by such a primitive method? It happened to me: I had fast-roped from a helicopter into a wooded mountain area. Through the trees there were a few discernable landmarks visible but it was difficult to orientate myself using my Army-issue map. After travelling for while, I began to suspect my compass (an Army Marching Compass) was not pointing due north and I was on the wrong bearing. I noticed several spiders' webs were pointing south-west according to my compass bearing. Most spiders build webs facing south in the northern hemisphere.  I reached a small clearing and decided to test my compass. It was an overcast day, which made it difficult, but the hazy sun was still casting a weak shadow. I made a rough check by using my watch and double checked by using a pole and shadow. My compass was way-out and I realised the mountain I was on must have a large iron ore content making my compass inaccurate.

Using a watch to find the North/South line as shown in the diagram above is only a rough-and-ready means of finding North. The sun rises in the east and  sets in the west in both hemispheres. At midday it is due south if you are in the northern hemisphere – due north if you are in the southern hemisphere. At 6am, it is due east, and at 6pm it is due west in both hemispheres. It moves between these points at a constant speed. Note: If your watch is set on daylight savings time, use the midway point between the hour hand and 1 o'clock to determine the north-south line or set your watch to GMT (Greenwich Mean Time).

So at 9am (GMT) the sun will be exactly southeast.

If the sun is very high in the sky, it can be difficult to judge its direction; in this case, place a straight stick vertically in the ground and align the watch hand using the shadow.

Using a straight stick:

If the sun is strong enough to cast a shadow, you can find the East/West line using a straight stick of about one metre in length.

Place the stick in the ground and mark on the ground the exact top of the shadow cast by the sun. Wait for 15-20 minutes and mark the exact top of the shadow cast on the ground in the new position.


Joining these two points gives the East/West line. West being the starting marker and East the ending marker.

Bisecting this line gives the North/South line.


A more accurate method:

A more accurate method, if you have all day: Attach a cord to the base of the stick and tie the other end to a sharpened peg. Adjust the cord so the peg reaches exactly the top of the shadow cast by the pole. Draw a clean arc at exactly this distance from the stick, by keeping the cord tight and scratching the line on the ground. As midday approaches, the shadow will shrink and move. In the afternoon, as the shadow lengthens again, mark the EXACT spot where the shadow from the stick touches the arc. Join the two points to give the East/West line. West is....of course, the morning mark.

By the stars

1) Less than 60 of approximately 5,000 stars visible to the eye are used by navigators. The stars seen as we look up at the sky at night are not evenly scattered across the whole sky. Instead they are in groups called constellations.

(2) The constellations that we see depends partly on where we are located on the earth, the time of the year, and the time of the night. The night changes with the seasons because of the journey of the earth around the sun, and it also changes from hour to hour because the turning of the earth makes some constellations seem to travel in a circle. But there is one star in the Northern Hemisphere that is in almost exactly the same place in the sky all night long every night. It is the North Star, also known as the Polar Star or Polaris.

(3) The North Star is less than 1° off true north and does not move from its place because the axis of the earth is pointed toward it. The North Star is in the group of stars called the Little Dipper. It is the last star in the handle of the dipper. There are two stars in the easily determined group of stars called the Plough or Big Dipper, which are a big help when trying to find the North Star. They are called the Pointers, and an imaginary line drawn through them five times their distance points to the North Star. There are many stars brighter than the North Star, but none is more important because of its location. However, the North Star can only be seen in the northern hemisphere so it cannot serve as a guide south of the equator. The farther one goes north, the higher the North Star is in the sky, and above latitude 70°, it is too high in the sky to be useful.

(4) Depending on the star selected for navigation, azimuth (The horizontal angle, 0 - 360 degrees, from a reference point, usually true north or true south. Also known as a bearing.) checks are necessary. A star near the north horizon serves for about half an hour. When moving south, azimuth checks should be made every 15 minutes. When travelling east or west, the difficulty of staying on azimuth is caused more by the likelihood of the star climbing too high in the sky or losing itself behind the western horizon than it is by the star changing direction angle. When this happens, it is necessary to change to another guide star.

The Southern Cross is the main constellation used as a guide south of the equator, and the above general directions for using north and south stars are reversed. Learn to recognise the Southern Cross. There is an obvious "line of stars," multiply the distance between the two outer stars on the line ("A" on the photo of the Southern Cross below) by 4.5 and extrapolate this line in the mind's eye. Below these two stars are the Pointers (see photo). Bisect the distance mid-way between the Pointers and where this line meets your extrapolated line is a fairly bright star which is directly above the South Pole. It takes a little practice but once learned it is easy to do.

The E&E compass in your Personal Survival Kit is not an accurate navigation instrument and is not meant to replace your main compass. If you need to use it, bear in mind that an E&E compass is only accurate to +/-5 degrees at the best, whereas a main compass will be accurate to +/- 0.5 degrees. Your E&E compass is meant to give a general idea of North, IN REAL TERMS IT STOPS YOU WALKING IN CIRCLES, important if lost in jungle, desert or travelling at night.

Experiment with any magnetised objects (knife, fish hooks) or objects with a magnetic field (battery powered watch, for example) to see at what distance they deflect the compass needle. Remember this when using the compass and keep it well away from such items