The Basics of Navigation

In Articles, Technical by Glyn DemmerLeave a Comment

You may have studied Geography (I did as part of the old TED syllabus) or served in the Defense Force where one of the modules given during basics was compass and map work (often presented by an extremely bored “Korporaal” who was more interested in chasing the troopies). In this day and age this is a neglected area, we all rely on a GPS which we use almost daily as we commute or head to the bush, so just about everyday we stare at the electronic map.

Time out, time to brush up on the basics at the same time learning an indispensable skill which could be useful if you GPS lets you down. So lets get started, invest in a decent compass which allows you to take an accurate bearing, then pick up a few maps, the best being the topographical variety available from the Government Printer ( now that’s a mission ) or a good map supplier.

Okay you now have your map but what does it tell you, well if it’s a 1:50 000 scale map that simply means that one centimeter on the map is equivalent to 50 000 centimeters on the ground (half a kilometer), the map also gives other invaluable information such as the description of the area and the location-where you are on the globe. This comes to you via the lines that run up and across the map known as longitude and latitude each line has a number either on the side or the top of the map; this allows you to calculate your location and express it as a way point much like your GPS.

Then there is the detail, the map shows all man made and natural features and uses symbols, colours and drawings to reflect them. Contours lines indicate gradient, if they are close together they indicate a steep slope and if further apart a gentler slope. This is important when planning a route, be it a hike, mountain bike ride or 4×4 excursion.

You will also see a schematic indicating North (think North Pole) known as True North (TN) and Magnetic North (MN) which is where the compass needle points. The difference is known as declination, in southern Africa this is 19°-20° West of True North and should be compensated for when calculating a bearing.

Before you start playing you will need to orientate the map, this can be done in two ways, either by using your compass and to indicate Magnetic North which you then align to the Magnetic North schematic on the map, alternatively you can align it using a combination of features on the ground, aligning the features on the map with the physical feature on the ground. The top of the map should then be pointing to True North.

Then it’s over to you, get out there and play, have fun with the kids and do something different ,get good maps and if necessary a book on using a compass, preferably written for the southern hemisphere. If you can’t get a book your compass should come with good clear instructions. Lastly start learning in terrain that you are accustomed to, it makes no sense to get lost as you are starting out!

Following the basics of navigation we’d now like to continue and touch on some GPS basics. Years ago I met someone who wore a watch on his left wrist and a compass on his right wrist, when I queried this he responded simply “What good is it to know the time if you don’t know where you are?” And that pretty much sums up the basics of navigation:
• You know where you are.
• You know where you’re going.
• You can calculate you’re estimated time of arrival or ETA (in the case of a GPS this is done for you using your average traveling speed.
• Dependent on your settings you can also calculate shorter routes or alternate routes to freeways and toll gantries.

From this you can see the key elements of distance, time and direction coming in to play. The term GPS stands for Global Positioning System, which is a satellite based navigation system introduced by the American Department of Defence. It provides accurate measurements of positions and altitude relative to sea level at any given time. The system uses satellites that cyclically orbit the earth. Using the signals generated by a group of satellites will allow your GPS unit to establish you position and altitude.

GPS ownership has grown exponentially and even though certain vehicles come with factory fitted units it is not uncommon to see a portable device mounted to the vehicles dash. TomTom and Garmin tend to be market leaders in South Africa with both companies using different base maps. So what does one need in a unit especially for going off-road into unfamiliar territory? Well affordability is critical as are the features necessary for on and off- road navigation.
• A good base map for the area or an ancillary update such as a “Tracks for Africa” map set. This will be seen on your “map page”
• A device that will give you your position and altitude as well as the time.
• A large enough screen.
• The ability to capture and store way points. Way points are what a GPS is all about, saving way points and going to way points.
• A screen that is readable in a variety of lighting conditions.
• Breadcrumbs or the ability to log a route is a very useful feature as you can view the route and all the key variables. (Time/distance etc).
• Voice guidance.
• A satellite screen that indicates the status of locating satellites when you switch it on and want to commence navigation.
• Portability is also useful when hiking or walking a route.
• The ability to upgrade the map set.
• Enhanced data from the map source such as points of interest with upgrades.

And then we get the features that are not critical but “nice” such as;
• Traffic reports indicating congestion
• Speed cameras indicating trapping
• Bluetooth phone synching is useful in town but not outdoors and many vehicle come standard with Bluetooth Integration. And lastly the least useful features are changing voices, vehicles, uploading photo’s etc.

Nowadays set up is quiet easy, adjust the screen lighting to an intensity that you are comfortable with set the time and ensure that you set the position format, in SA we use the WGS 84 datum format. Many units allow you to customise the display according to the information you require, I always like to see the speed I am traveling at as car speedometers are often out by a % , it’s also useful when setting cruise control and in areas where speed traps abound( most of SA).

As I take a lot of photo’s the time of sunrise and sunset is useful and the most important setting is the ETA (Estimated Time of arrival) that helps plan a route, stops and fuel. When you mount the device keep it in the centre of your dash in a position that the aerial is able to pick up the satellites signal, avoid putting your GPS close to a window as ‘smash and grab’ hotspots are common in most towns in SA. Then avoid adding your home address as a way point known as “home”. If you are ever high jacked the criminals can find their way directly to your home. Rather just key in the physical address!

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