Never mind ‘How ya goin?’, ‘Where ya goin?’ and can you get yourself there safely?
Words and photography by John Cadogan
When it comes to essential equipment for a serious off-road exercise, maps, compasses and a GPS are right up there with water and fuel - and beer, let’s not forget that.
In relation to maps, however, I reckon it’s pretty hard to beat the printed-on-paper kind. Electronic maps keep getting better, but they haven’t replaced their paper counterparts just yet. At best, they’re an interesting adjunct. The sort of thing an Xbox addict might get off on in the scrub. Sure, every time you blink you seem to be able to stuff ever-greater amounts of map data into ever-smaller GPS receivers, but a central problem remains: you’re still looking at a tiny LCD screen.
No matter how efficiently you zoom in and out, you can’t really see the big picture when you look at it through the tiniest of battery-powered windows, and remember, paper maps don’t run out of batteries... This is a story about getting the basics of map, compass and GPS under control. Without these skills under your belt, you’ll be flying blind every time you go bush, or worse, you’ll be putting your trust, and potentially your safety, in the hands of someone else. Let’s start with maps.
WHAT MAPS ARE
Everyone who’s ever used a street directory has used a map. They’re so similar, maps and street directories, that only their mothers can tell them apart. A street directory helps you get from a known location (say, home) to a place you’ve never been (say, the mother-in-law’s house). You look up the coordinates of the unknown location (that’s the grid reference - J8, map 112 or something - in the street index up the back) and then plan the route. You follow the map(s) on the way there by verifying your position along the way using known geographic features off the street directory (intersections, Sydney Harbour Bridge and so on).
The process is identical when you use a 4WD map, only there are three main differences.
First, the maps aren’t cut up into pages. Second, there are fewer geographic features and no index of the street names. Last, there is a more advanced coordinate system - C5 is replaced by latitude and longitude - but it works just the same.
SCALES FOR 4WD
Australia, funnily enough, is a big place. Much of it has not much in it, which is why we tend to use large-scale maps. These cram a large amount of terrain onto a manageable sheet of paper. Auslig, the Federal Government’s geographic information agency, has the entire continent mapped in the 1:250,000 scale, which means you can buy a topographic map of anywhere in the country at that scale. Incidentally, 1:250,000 merely means 1cm on the map equals 250,000cm (that’s 2.5km) on the ground. Some of the country is mapped at other scales. (1:100,000, 1:50,000 and 1:25,000 are common. In mountainous terrain, such as the VIC Alps, 1:50,000 can be helpful.) However, official topographic maps aren’t really all that user-friendly for us four-wheel drivers.
Thankfully, organisations like Hema Maps use Auslig’s data and its own in-house specialisation to churn out maps ideally suited to the four-wheel driver. They combine the best features of both topographic and touring maps, which makes them uniquely user-friendly. Hema’s Simpson Desert sheet is a top example. It’s printed both sides. One side is real ‘big picture’ stuff. At 1:2,500,000 (1cm = 25km), it spans all the ground between Alice Springs and Birdsville. That’s a lot of dirt. The flip side, at 1:500,000 (1cm = 5km), is better for coming to grips with just the desert crossing. It has Birdsville in the east and Mt Dare in the west. One of the other really neat things about a specialist 4WD sheet like Hema’s Simpson Desert is that the hard work of figuring the coordinates (the latitude and longitude equivalents of the street directory’s B6) of all the important track junctions and fuel-supply points has already been done for you.
COORDINATE SYSTEMS
The surface of the earth is two-dimensional. Sure, it’s curved into three dimensions thanks to Columbus, but the surface is two-dimensional. That’s good, because in two dimensions only two coordinates are required to specify your position. Generally, us four-wheel drivers use latitude and longitude, but another system called the Map Grid of Australia (MGA) also exists. Conventional lat/long is the most common by far and also the one Hema uses for its specified ‘waypoints’ (points of interest). Latitude lines slice the earth from west to east like onion rings. They start at 0° at the equator and go up to 90° at the poles. We’re in the southern half of the world, obviously, so the letter ‘S’ always follows our latitudes.
Longitude lines are the big, long lines that go through the poles and carve the earth up like the slices of an orange. Zero degrees is through Greenwich in the UK. Longitudes go to 180° maximum (directly opposite Greenwich is 180° longitude). Australia is in the eastern half of the world, so the letter ‘E’ follows all our longitudes. If you go about 26° south of the equator and 139° east of Greenwich, you pretty much fall into the front bar at the Birdsville Hotel. You can’t be in any other place. Degrees on their own aren’t a particularly useful unit for navigation because they’re too big. It varies, but one degree is about 100km (ballpark approximation).
Degrees are each divided into 60 minutes. A minute at the equator is a nautical mile: about 1850m (ballpark: about 2km). Minutes, in turn, are divided into 60 seconds. A second is about 30m. For most 4WD work, remember that if you can get to within 10 seconds of the required location, it’ll be within (say) 0.5km in every direction.
COMPASSES
Despite GPS, a compass remains an essential navigation tool. The best and most common kind is the Silva-style orienteering compass. It’s the one with the transparent base and the bezel that rotates relative to the base. Most GPS receivers don’t function very well as compasses. Most don’t function at all as compasses unless you are moving. A compass is essential, because GPS is not a perfect navigation solution for dummies. The three biggest problems with using just GPS are first, you need to key in the coordinates of the objective. Most degree/minutes/seconds coordinates are 13 digits long.
You might have to input 30 such ‘waypoints’ for a Rig Road Simpson crossing. That’s a total of almost 400 digits. If you’re 99 percent accurate, you’ll still get four of them arse about. Second, your GPS receiver might die in service, or you might lose it, leaving you in a navigational black hole. Third, some nut-job terrorist might fly another plane into the GPS Master Control Station in Colorado Springs, or some (presumably different) nut-job in the Pentagon might get an attack of the conspiracies and flick the big, red ‘GPS off’ switch.
GPS RECEIVERS
At the risk of generating more hate mail than a fit bloke can jump over, all GPS receivers are the same - at least in terms of their ability to tell you where you are. They’re all very damn good at that. They’re also all equally good (or almost so) at locking onto satellites on start-up. We’re talking about the current models here. Some of the museum pieces from 10 years back took forever. Everything else is fruit. Some of us like apples, and some of us like oranges. Personally, I like being able to input waypoints pretty easily.
I also value long battery life for the times I’m on foot or in my kayak, but I like being able to plug into the vehicle’s ciggie-lighter 12V supply when I’m in the 4WD. That saves batteries. Waterproof is good. If it floats, better.
Pocket-sized is great, but a recessed power button is essential, because it’s no good if the thing gets nudged on as you walk and then goes flat. A decent price point is also a great idea, because the damn things keep getting better, and you maybe don’t want to be locked into the one that cost megabucks back then when a better one is available for much less money now. Personally, multi-coloured displays, the capacity to play games, hook up to a PC or PDA, store 12,000 waypoints or all the maps of eastern Europe at 1:50,000, having a built-in barometric altimeter and so on, don’t feature all that high on my personal value scale. I reckon you can get a GPS receiver with all the smart bells and whistles (and some of the dumb, unnecessary ones as well), plus accessories like a lanyard and a 12V power cable, for well under $500. It’s a top investment, because GPS takes all the hard yards out of navigation - just don’t rely on it totally.
PUTTING IT ALL TOGETHER
Tick the boxes before you head off. All the pertinent maps, your compass, your GPS and spare batteries all need to be there. If you have time, input the important waypoints before setting off. Alternatively (provided you don’t get motion sickness), you can do it from the passenger’s seat while someone else is carving up the easy highway kays between home and the scrub. When you’re in a remote area, mark your position on the map. Use a pencil, which won’t explode ink everywhere in the heat, but even better, which won’t smudge and run if the map gets wet (rain, sweat, coffee...). Keep track of where you are on an ongoing basis. Say, every hour or so. That way, if you do get lost or disoriented, GPS or simple backtracking can get you back to your last known location, and the most you’ll lose is two hours.
Don’t underestimate the value of your vehicle’s trip meter. Most of the time you'll be following tracks that are linear features (even if they’re not straight lines). There’s no better feeling in the navigation world than to estimate where you are on the map based on your previous position and how far you’ve come based on the vehicle’s trip meter. Then you can crank up the GPS and have your take on the whole ‘you are here’ scenario confirmed by those high-tech signals from space.
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