Basic navigation skills. Laying the foundation.
Text: Kobus Bresler. Article from the August 2012 issue of DO IT NOW Magazine.
“If you don’t know where you are going, you will probably end up somewhere else.” – Dr Lawrence Peter
“Map and compass?” he asked with a look of amazement. “I have my GPS packed so I will be fine.” The look of confidence combined with the smirk on his face got me upset. I am not sure how his hike went, but the lack of communication afterwards probably meant it went badly. Sadly, this type of response is quite common and very worrying for those of us who still believe basic navigational skills are what will get you through a sticky situation.
When you study the art of navigation to its full extent it may be overwhelming. There are many different tools available and lots of different ways to combine them. The terminology alone can be challenging, with words such as resection and azimuth to name a couple. Like anything, navigation starts with a basic knowledge of relatively simple concepts. Numerous books have been published on this topic as navigation is an exact science. As a result, many skills can be learnt from text books, but please note that no book or article can replace proper instruction. In this issue and the next I will go through some of the basics used for navigating on land in South Africa, and this will lay the foundation for learning more advanced techniques.
Every year thousands of people explore the natural splendour our country has to offer. Accidents happen and it costs thousands annually in rescue costs, and sometimes even a life. Too often these accidents occur as a result of poor navigation skills. There is no point having a map and compass, or a GPS, and not knowing how to use it correctly. The starting point of any hike or adventure is choosing the appropriate areas to explore, but be careful not to stretch yourself beyond your abilities or level of experience. Our country offers amazing opportunities for people of all experience levels and as your skills improve, your possibilities will increase too. We often learn from bad judgement calls, so it’s best to make these in an environment you are comfortable with and can turn the situation around.
The route
Route planning is essential prior to any trip and basically means determining your lines of travel. This starts at a specific point and leads to your ultimate objective, and is mostly determined by studying a map. When planning your route you need to consider the time you have available, as well as your personal abilities and that of the people with you. It is inevitable that your route will change once you get going, as not all features are always clear on a map, but having a basic plan is essential. It is important to gather information about the area you are going to. Obtain the correct maps, check weather reports, explore difficulties and determine the nature of the terrain. Local knowledge is the best and most precious knowledge you can have.
Common sense will often be your strongest attribute. When route planning consider the weight each member of the party will be carrying, as unnecessary weight can slow you down significantly.
The Map
It all starts with a map, but no matter how good the map it remains worthless unless the user knows how to read and use it. A map is a symbolic representation of the earth or a portion of it on a flat surface. Many types of maps have been printed to suit different needs and in South Africa most outdoor navigators prefer to make use of 1:50 000 topographic maps.
These maps portray terrain features in a measurable way. The horizontal positions of features are represented and the vertical aspect, or relief, is normally represented by contour lines. Be sure to look after your map and keep it protected because it’s your most valuable tool and the focus of this article.
A proper topographic map will have the following information:
- Sheet name – A map is normally named for the largest settlement on it or the largest natural feature.
- Sheet number – The sheet number is used as a reference to link adjoining maps.
- Scale – A representative fraction,that gives the ratio of a map distance to the corresponding distance on the garth’s surface.
- Line scales – Rulers used to convert map distance to ground distance.
- Declination diagram – Indicates the angular relationships of true and magnetic north.
- Contour interval – States the vertical distance between adjacent contour lines on a map.
- Map edition and date – The map date is important to determine how accurate the map data will match what you will encounter.
- Datum – Describes the model that was used to draft the map and is of particular use when setting up a GPS or other tools.
- Grid System – Horizontal and vertical points or lines covering the complete map area that are used mainly for positioning.
Grid lines and references
Grid lines divide a map into smaller areas to make identifying a specific point more accurate. Various grid systems are used around the world, but the most common one used by hikers locally is an angular coordinate system, by determining latitude and longitude. The grid lines used in this system are a set of east west rings that cover the globe and run parallel to the equator. In addition, north south rings cross the equator at right angles and converge at the poles. This forms a grid from which any point on earth can be located. When a position is calculated we express it in a numerical format and call it a grid reference or coordinates, like in the example shown.
Read and learn as much as you can about grid references, and practise until you understand how to calculate a position. Also make sure you can determine a position on a map from reading a coordinate. This is such an important basic skill. Imagine how much time, money and lives will be saved if all hikers that contacted emergency services could supply their exact position.
Map scale and distance
The scale of a map is the ratio of the distance between two points on the map and the actual distance between the same points on the ground. The scale allows us to convert distance on the map to distance on the ground and vice versa. This ability is an important factor when navigating outdoors. The map scale is expressed as a representative fraction, for example 1:50 000, and in this example the one unit of measure on the map is equal to 50 000 units of the same measure on land. Measuring between two points on a map and multiplying with the scale gives you the actual ground distance between the same two points. Most decent maps will show a line scale or ruler, which is a straight line indicating units of measure and its equivalent distance on land.
It is important to understand that map distance does not take into consideration any vertical changes on land and must be considered a flat distance. Therefore, the distance covered on land will increase as you proceed and should be taken into consideration when route planning and navigating. Study a few maps and calculate distances using the scale until you understand it. This is another vital skill needed to navigate accurately in any environment.
Map legend
The purpose of using a map is to visualise an area of the earth’s surface and features within that area. Most decent maps have a legend that explains the symbols found on the map. The mapmaker uses these symbols to represent natural and manmade features. A series of colours are used on most commonly found maps, such as blue depicting water and green representing areas of vegetation. By making use of accurate terrain association you can effectively navigate even without a compass. A decent map is the most important tool in your navigation kit.
Contour lines
A contour line represents an imaginary line on the ground and runs along a constant altitude. The start point for the vertical measurement of elevation is mean sea level. This is the point halfway between high and low tide. Elevation of any point on earth is its vertical distance above or below mean sea level, and is depicted by contour lines on topographic and some other types of maps.
The vertical distance between contour lines on a topographic map never changes. The contour interval will be noted on the map and is important to understand if you are to navigate effectively. Most 1:50 000 topographic maps in South Africa have a contour interval of 20m. It does not represent the actual distance between the contour lines and only shows the elevation change. This is just one example and maps differ, so you will need to find this information on the map you will be using. With this information you can easily determine what the terrain will be like in the area you are going to move through. The further apart the contour lines the flatter the land, and the closer they are the steeper it gets. Touching contour lines represent a vertical drop, but contour lines can never cross.
On standard topographic maps every fifth contour line is more prominent. These are known as index contour lines and are numbered, at some point, to show its elevation. Before calculating elevation of any point on a map you will need to know the contour interval. Determine if you are gaining or losing elevation by finding the nearest index contour line and then count the lines from your position to the index. Multiply this number with the contour interval and add or subtract from the elevation of the index used. Contour lines have many other uses that will be learnt through experience, such as determining the shape of the terrain.
It is important to understand and apply the basic skills mentioned, which will lay the foundation for learning more advanced techniques and improving your map reading and navigation skills. Further reading and practise will refine these skills and allow you to safely start exploring more of the amazing wilderness areas found in South Africa. In the next issue we will look at basic compass and GPS skills and how to combine them with map reading. Until then, happy trails and be safe!
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