Find your way with a GPS

By Allen Macartney

TWO FRANTIC paddlers beached their canoe at my wilderness camping site in Algonquin Park. Distraught, they waved from waters’ edge and shouted, “Can you tell us where we are?”

“Sure,” I said, putting down the frying pan and approaching the pebbly, little beach. “Where’s your map?”

“We’ve got a GPS,” one of them said, proudly presenting it skyward.

“Great,” I replied. “But where’s your map?”

Since prehistoric times, travelers have been getting lost and seeking a reliable means to find their way. Cavemen used twigs and stones to mark their route to distant hunting grounds. Ancient mariners hugged the coastline to avoid getting lost and falling off the edge of the earth. Phoenician traders depended on the North Star to navigate around the Mediterranean Sea. Vikings used a magnetic, fish-shaped piece of metal to wend their way to the next Atlantic coastal village ripe for plunder.

Today, global positioning systems (GPS) have removed much of the uncertainty of wilderness and urban travel. With the push of a button, a GPS can tell you exactly where you are almost anywhere on the face of the Earth—from the market in Ottawa to its counterpart in Patagonia, Argentina.

Have you ever found a perfect fishing spot where the fish practically jumped into the canoe? With a GPS, you can hit a couple of buttons and lock in that exact location forever. My own GPS

can save almost 1,000 locations, called “waypoints.” The saved data helps you to return to the exact spot whenever you wish. By following the GPS compass heading, you can determine the distance from your destination, your current speed, and how long it will take you to get there at that speed.

How does it work? A constellation of 24 satellites (21 active with three operating spares) circles the Earth in synchronized orbits at an altitude of about 17,000 kilometres. Travelling at 11,000 kilometres an hour, and equipped with precisely calibrated clocks, the satellites transmit the exact time and position at the speed of light. On the ground, a GPS receives the satellite signals, measures the time it took for the signals to reach it, and calculates its position using triangulation. At any one time, up to six satellites are “visible” in the sky to your GPS. It must be able to lock onto at least three satellites to calculate a position accurately. The more satellites the GPS can contact, the more precise the calculation.

My own GPS, a Magellan SporTrak Colour, provides accuracies to three metres almost anywhere on Earth. Less expensive models can usually provide accuracy between 10 and 100 metres.

GPS is widely used by soldiers, mariners, aircraft pilots, backpackers, canoeists, surveyors and others. Small wonder that French and English digging crews starting on opposite sides of the English Channel were able to meet in exactly the right place when they built the Chunnel. GPS is a boon to mapping

and surveying companies whose reputations depend on pinpoint accuracy.

Wildlife biologists have fixed GPS systems with micro-transmitters to track threatened species, like the Mojave Desert tortoise. GPS-equipped balloons are monitoring holes in the ozone layer in Antarctica, while marine buoys track major oil spills by transmitting GPS data.

Should we rely solely on technology to keep us informed? Just like our bewildered friends on the beach in Algonquin Park, having a GPS doesn’t mean your old compass and map should languish in the closet. GPS has not made maps obsolete. On the contrary, maps will enhance GPS capability and should not be considered mutually exclusive. Paper maps provide the “big picture” for planning your route around pesky obstacles and leading you to those beautiful “must-see” locations.

Consider the time my son and I were planning a weekend cycling trip over a rough trail we’d never seen. Our maps identified a two-kilometre section early in the trip as difficult for cycling. We had some questions: How bad is the trail? Is the distance accurate? Will we have to carry our bikes and camping gear? The GPS helped clarify the situation and proved the map wrong. The rough section was actually 1,157 metres long and very “do-able.” Our high-tech gadget gave us an edge by removing doubt and boosting our confidence.

Lost and found

The main reason people buy GPS units is to help them navigate easily from point to point. GPS units with midrange to advanced capabilities contain pre-loaded city and topographical maps. Some don’t provide many details and are limited to showing major roads, railways, rivers, lakes and airports. More expensive models like my Magellan have detailed maps that even show contour lines—great for snowshoeing, backpacking, rockclimbing and cycling trips. They have 8, 16 or 32 megabytes of RAM memory to accommodate downloading detailed maps from the Internet.

Some bare-bones, inexpensive GPS units don’t have built-in maps. They provide little more than your coordinates, so

you need to cross-reference the readings with a map to find your exact location. Those intrepid (but under-equipped) paddlers I met in Algonquin had this type of GPS. Most low-end models also show other details, including your speed, direction of travel, and distance to various locations (e.g. your home, car, or cottage).

As you walk, paddle, cycle, drive or ski, all GPS models automatically record your journey on a visual track log that looks like an electronic trail of bread crumbs. This dotted line trail appears on your GPS screen by recording every twist and turn you take. GPS tracks overhead satellites constantly, so if you become disoriented, you can retrace your route along the bread crumbs to your campsite or car. Just remember to record your starting point before you leave. If you saved the position of your campsite or car as a waypoint, you can ask your GPS to calculate a more direct return path via its “Go to” function.

Can you use a GPS anywhere? Yes, but you might encounter problems in a cave or underground parking garage where satellite signals might have penetration problems. As well, expect less accurate readings if you’re hiking under dense tree cover because satellite signals can be scattered by the leaves. Urban travelers sometimes experience difficulties from satellite signals bouncing around off skyscrapers, too.

Dollars and sense

Most people buying a GPS settle for an entry-level model that costs between about $160 and $200. These are great as long as you’re just looking for basic features that do not provide an electronic map. Spending an extra several hundred dollars buys a model chocked full of advanced features that could ultimately prove worth the extra investment.

My Magellan GPS is an upscale model with a back-lit colour display that makes reading pre-loaded topographical maps simple. The colour screen highlights the location of everything from large bodies of water to mountain peaks to contour lines. My GPS even has a special weather feature that measures barometric pressure and other details to provide a fairly accu

rate 48-hour weather forecast. All this and it weighs about as much as a large tube of toothpaste. Incredible!

Soon after purchasing at least a mid-range model GPS, many people enjoy the challenge of advanced wilderness navigation and geocaching games (see the sidebar story). Advanced GPS models allow for future growth as you get more comfortable with navigation.

They permit optional map downloads, and the more expensive the GPS, the more detail its built-in maps tend to provide.

Before heading out on the trail with a GPS, get to know your model. Don’t take it out of the box and head straight for outback, like my hapless campsite visitors. Your adventure may turn out to be much more exciting than you planned!