Outdoor tech: GPS navigation

By Dean Mellor 24 November 2015
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Civilian GPS receivers have come a long way since they made their debut in the early 1990s, and they make navigating easier than ever.

DESPITE ITS INVOLVEMENT in wars, humanitarian efforts and geopolitical power struggles, it could be argued that one of the biggest impacts the US Department of Defense has had on the world in which we live today is the development and implementation of the Global Positioning System (GPS).

After all, people the world over rely on GPS every day for all manner of tasks, from finding someone’s address on a satnav or phone to piloting a passenger plane or container ship across the globe.

Obviously GPS has also had a huge impact on the way adventurers navigate the great outdoors. We need no longer rely on paper maps, compasses and rulers to find our way around in even the most remote and isolated parts of the planet; now we just need a capable GPS receiver loaded with the right mapping software and an ability to keep its batteries charged… although paper maps are always a great back-up in case of a technological mishap.

History of GPS

In the 1970s the US Department of Defense kicked off its GPS program, which was originally intended to be exclusively for military use. When finished in 1995, it consisted of 24 satellites orbiting at an altitude of 20,200km giving coverage of the entire globe, along with a few spares in case any of the satellites ever malfunctioned. Today, there are more than 30 satellites in the GPS network that are technologically superior to the originals.

When the USSR shot down a civilian passenger plane (KAL-007) in 1983 after it strayed into foreign airspace, then President Ronald Reagan announced that the GPS network would also be available for civilian use, albeit without the accuracy available to the US military; civilian GPS signals were intentionally degraded through Selective Availability (SA) for national security reasons. The result was that consumer GPS receivers could give a reasonable position fix, but they could be out by up to 250m; not ideal if you’re trying to navigate while flying a plane, or trying to choose between two seemingly parallel tracks when navigating in the bush.

In May 2000, then President Bill Clinton announced that SA would be switched off for good, giving civilian users of the GPS network accuracy down to just a couple of metres and, in doing so, revolutionising the way we use GPS in devices like satnavs and smartphones.

Not wanting to depend on the US GPS satellite network, the Russians developed their own satellite navigation system called GLONASS (Global Navigation Satellite System), which consists of 24 satellites. Although similar in concept to GPS, GLONASS satellites have a slightly different orbit to GPS satellites and emit slightly different signals, although there are now a number of consumer GPS devices that make use of both GPS and GLONASS signals.

On the consumer front, early GPS receivers were very basic by today’s standards. By the mid-1990s there were a number of manufacturers including Sony, Panasonic, Eagle, Silva, Magellan and Garmin, but some of these companies have either dropped out of the GPS receiver scene completely or consolidated with other manufacturers.

With more basic antennas, early consumer GPS receivers took longer to acquire satellite signals and were less able to do so in forested terrain than today’s high-tech units. And unlike today, there was no mapping software, so your position was displayed on a grey LCD screen in latitude, longitude and altitude coordinates which you would then have to plot on a paper map (and SA sometimes made that a hit and miss affair). Other functions included heading, track, speed and time, as well as the ability to mark waypoints and create routes.

The other drawback with GPS receivers in the mid-1990s was their insatiable appetite for alkaline batteries; you’d have to carry a bag full of them to keep the units operating out in the field.

How does GPS work?

The orbits of the GPS satellites are arranged so that there are at least four satellites visible at any given time anywhere on earth, which is important because your GPS receiver needs to receive the signals from at least four satellites to calculate your precise position on the earth’s surface.

The GPS satellites transmit information about their location and the time (which is measured with onboard atomic clocks). Those signals are picked up by your GPS receiver, which calculates its precise distance from each satellite.

Armed with this information, the GPS receiver uses trilateration to calculate your position on earth. This position fix can be achieved with the signals from just three satellites, but to get a more accurate fix, as well as give you information about your altitude, your receiver needs the signal from four satellites.

As you’ll no doubt be aware, the GPS signals can’t be received indoors, and it takes longer to acquire a position fix if there’s foliage overhead, or even on a cloudy day, but if you have a clear sky you’re bound to pick up the signals from four or more satellites relatively quickly. If your device allows it, using the GLONASS network in addition to the GPS network can improve your chances of acquiring a satellite signal in unfavourable terrain. In fact, according to Garmin, “With an additional 24 satellites to utilise, GLONASS compatible receivers can acquire satellites up to 20 per cent faster than devices that rely on GPS alone.”

Many devices, including a number of smartphones, such as iPhones and many Android phones, use both GLONASS and GPS.

Best GPS device for outdoor touring

If you plan on using a GPS device to navigate on a remote-area trip, or in harsh terrain, then you’ll need a dedicated device rather than just a smartphone. There are a number of manufacturers of said devices including Garmin, Magellan, Lowrance and DeLorne, and they make a wide range of products suited to different pursuits such as sports, outdoor adventures, off-roading and fishing.

There are several factors to take into account when selecting an appropriate-for-use GPS receiver, such as ability to withstand the elements, size and weight, screen size and resolution, battery life (and ability to recharge the batteries), navigational and mapping features, as well as the availability of mapping software.

Most outdoors GPS receivers are loaded with a base map that will include information such as roads, lakes, rivers and points of interest. In addition, they offer the ability to view satellite imagery or upload topographic maps so you can navigate in detail.

A dedicated outdoor GPS receiver will also allow you to pre-plan your trip in detail on a PC (even offering the option of a 3D view so you can zoom in and out, rotate the map and ‘fly through’ the terrain) and then load the information into your GPS receiver.

Finally, at the end of your trip, you can download all of your data from the GPS receiver to your PC, allowing you to relive your adventure in 2D or 3D. All of the GPS receiver manufacturers have their own software so it’s worth investing some time to make sure you choose the one with the features that best suit your outdoor needs.

A favourite GPS device for Australian four-wheel drivers and tourers is the Hema Navigator, which is preloaded with all of the company’s excellent 4WD maps, as well as topographic maps covering all of Australia.

The easy-to-use device has a seven-inch touchscreen and it features both street and 4WD navigation. Another alternative is to purchase Hema Explorer mapping software for use on GPSenabled devices such as iPhones, iPads and Android phones and tablets.

Offline, it includes Australia-wide 1:250k topographic maps and 1:1M Hema touring maps, has more than 40,000 points of interest four touring, camping and four-wheel driving, and allows you to navigate and record with real-time GPS tracking. Online it also features map-overlaid radar and weather forecasts, and access to shared trips through the Hema Explorer Cloud track database.

There are several other satellite navigation apps available for smartphones and tablets, all of which can turn your device into a substitute for a dedicated consumer GPS receiver, but your phone won’t be nearly as robust and is not suited to extreme conditions.

The latest trend in GPS devices is the smartwatch, of which there are various styles and designs suited to different tasks such as sports and fitness, adventure activities and simple about-town navigation. Sports watches can be used like personal trip computers that record your data allowing you to calculate things like total route distance, average and maximum speed, heart rate and more.

Adventure watches are designed to act like a traditional outdoor GPS receiver, and one example, the new Garmin epix, offers full-colour mapping and makes use of both the GPS and GLONASS networks. It has a 1.4-inch screen, a worldwide shaded relief base map, 8GB memory so you can upload topographic maps and satellite imagery, altimeter, barometer and compass, and it can even link to Bluetooth compatible devices so you can access email and text messages, keep an eye on the weather, relay your position to others and more.

Modern GPS receivers have come a long way in a short period of time, and outdoor enthusiasts are amongst the biggest beneficiaries of this technological progress. It wasn’t that long ago that we relied solely on paper maps, magnetic compasses and rulers… can you imagine planning your trip and navigating that way these days?

Remember though, if your GPS device fails in the bush, you’ll still need a paper map, and just as importantly you’ll need to know how to read it and how to navigate using traditional methods.

Source: Australian Geographic Adventure September-October 2015