Basic Navigation Skills – Laying the Foundation, Part 2
Text: Kobus Bresler. Article from the November 2012 issue of DO IT NOW Magazine.
In the previous issue I discussed the basic skills needed to effectively use a topographic map when navigating outdoors. It is important to understand and learn the basics, which will lay the foundation for learning more advanced techniques.
Your skills will improve over time and make for a safer and more enjoyable experience out on the trails and in the mountains. In this issue I will continue to look at more basic skills, with a specific focus on compass use. It is nearly impossible to effectively learn compass use from text, but a few key skills will be highlighted. More important is choosing the correct compass and features when selecting a model for purchase.
Nowadays most outdoor navigators make use of GPS technology. A standard handheld GPS is an amazing tool and if used correctly allows for pinpoint accuracy. It is an electronic device and makes use of batteries. The human factor can potentially be a problem, as GPS models are reliant on correct human input to work effectively. So what happens if it fails? We revert back to the basics of compass use.
A compass combined with a decent map remains the primary navigation tool when moving about outdoors. There are many different models available, but your selection should be lightweight and compact. The ideal compass must stand up to every-day bumps, and should be easy to understand and use. Standard map compasses have a baseplate and compass housing, but a decent model will also have a ruler, roamer and more features for advanced use. Some navigators prefer a ranger compass, which essentially is a map compass with a mirror, while others may prefer a prismatic compass. We will focus on the basics of the standard map compass as it is the most readily available and widely used compass by amateur navigators.
Compasses can either be ‘dry’ or ‘wet’. A wet compass has a liquid damper inside the compass housing, which allows the compass needle to settle faster due to less sensitivity. Although most map compasses use a needle, it is still fairly common to find models using cards. Cards generally settle faster than needles, but in return needles are more durable. It is important to invest in the best compass you can afford, as one day your life may depend on it.
As your compass is a precision instrument you should care for it accordingly. Avoid dropping it and handling it roughly, and try to keep it clean. Protect your compass from magnetic fields and extreme temperature changes as this will affect its continued accuracy. You should check your compass periodically on a known line of direction, and any compass with a variation greater than three degrees should be replaced. Often a bubble forms inside the compass housing of a ‘wet’ compass as a result of abuse, and this will allow air to enter the housing. The bubble will interfere with the needle causing it to be a few degrees inaccurate and therefore no longer good for use.
Continued exposure to strong magnetic fields may cause reverse polarity to occur. Basically this means that the south end of the needle will point north and vice versa. If this is unknown to the user it can cause obvious problems and mistakes. While using your compass avoid magnetic fields of any sort, such as power lines or metal objects. Any such interference will cause magnetic deviation, which forces the needle away from the correct direction.
Because of the earth’s magnetic field and curvature the needle will try to point directly to the magnetic north pole. When standing in South Africa this point will be underground and as a result the needle will dip. A compass needle will need to be perfectly balanced to avoid touching the top or bottom of the housing. This ‘dip’ is commonly referred to as magnetic inclination and will affect the accuracy of your compass reading. As a result compasses are balanced for different international zones, so be sure to purchase the correct one for use in Southern Africa, or wherever else you may be navigating.
The ruler found on your compass is useful when determining distance covered in conjunction with your map. Practise this skill until you are comfortable using it accurately. Most decent map compasses will have a roamer printed on the baseplate. Roamers are aids used to increase your accuracy when determining grid references and are used in conjunction with a topographic map. Learn to use the roamer effectively as it takes the guesswork out of grid references. You can also make your own roamer based on the maps you use and I highly recommend having this tool available. Take a look at the picture found in the text to understand the simplicity of this aid.
When visibility is good most navigation can be done visually without a compass and is called terrain association. To ensure this is done accurately the map needs to be orientated so that it is correctly aligned with the earth.
Orientating a map means that the features shown are in the same relative position as the earth. There are two main methods used to achieve this: terrain association and compass orientation.
By using terrain association the user can make quick references as they move across the terrain. The user will have to know the approximate location, and careful examination of the land and map features is needed. Once you have orientated the map it is possible to locate the relative position of features in your vicinity. Practise this skill as often as possible because it is one of the easiest things to get wrong.
Orientating a map is a lot more accurate if you use a compass. When using a compass, always remember that it measures magnetic azimuths or bearings. You will need to convert this to true north by making use of the declination diagram on your map. If you have never done this before it is hard to learn this skill from text and you may need instruction and lots of practise. Any small mistake during this process will result in navigating in the wrong direction.
Compasses have numerous other uses that you can learn over time, but it all starts with the basics. The most important aspect to take from this article is choosing the correct compass in the first place. You generally get what you pay for and a decent compass will go a long way towards ensuring your safety and that of the people around you. Once purchased take care of this precision tool so that it can help guide you in the right direction. If you practise these basic skills it will open a whole new world of exploration and possibilities.
Proper instruction can never be replaced by any textbook, so if you are unsure of certain aspects find someone that can assist you.
Happy and safe hiking.
Follow these steps:
2. Find the declination on your map and set the north arrow accordingly.
3. Place the compass on the map, with the direction of travel arrow pointing north along the grid lines.
4. Rotate the map and compass until the needle coincides with the orienting north arrow.
5. The map will be correctly set in relation to the features on land and accurate navigation is now possible.
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