 GPS map showing where each car ran out of gas. Note that the label for the Ford Focus is hidden behind that of the Spectra; the Civic’s is obscured by the Corolla’s, and the Mitsubishi Lancer’s label is hidden by the Pontiac G5’s.. Click image to enlarge |
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By James Bergeron
When we set out on the first Autos 50-litre ChallengeTM back in 2005 I came armed with my GPS just for fun. We were somewhat naive when we intended to allow critical data, like mileage driven, to be recorded from each car’s odometer. Having the GPS back in 2005 was a blessing when some trip odometers had mistakenly forgotten to be reset at the onset of the trip.
Fast forward to 2008 and the second Autos 50-litre ChallengeTM: being the “geek” of the group, I was tasked with bringing my GPS along with me once again, though we were still going to rely on the odometer readings in the vehicles.
Vehicle speedometer and odometers are not exact devices. They are calibrated within a tolerance range when each vehicle rolls off the line and for the most part is never to be touched again. Many factors can affect your speedometer and odometer, the most obvious being tire wear.
Typically, your speedometer will read higher than your car’s actual speed. When your speedometer reads 100 km/h you may actually be travelling 96 km/h. In some ways, this is great: it saves us from the dreaded radar gun, but it also means your odometer is covering more distance than the car is actually travelling. In the above example, it’s 4 per cent more. Over 1,000 km, this adds up to an extra 40 km which would invariably throw all of our numbers off.
In comes the GPS to the rescue, which is perhaps not 100 per cent accurate itself. Using mapping software in conjunction with the GPS device we are able to achieve consistent results. The GPS device I used is a Garmin iQue 3600. It’s fairly old technology by today’s standards but it provided us with the ability to not only track the driven route, but to plot each vehicle’s demise on a map.
The concept is fairly simple – the GPS was with me and on at all times during the day as we rotated through car after car. The device communicates with the GPS satellites in the sky to triangulate our whereabouts. The software built into the GPS contains two key features: the ability to track your movements and save them and the ability to create waypoints along the route with exact coordinates. We used the latter feature to record where exactly on our journey each vehicle ran out of fuel, and the former to map our progress on the computer afterwards.
Having a consistent and fairly accurate device to plot each vehicle along the route turned out to be invaluable. Relying solely on each vehicle’s odometer would not have provided consistent results as was painfully obvious when the Dodge Caliber’s odometer read 677 km when it ran out of fuel while the Volkswagen City Golf’s odometer read 2 km less at 675 km when it ran out of fuel; yet the Volkswagen City Golf clearly travelled further on our route than the Caliber.
Most of the vehicle odometers were close; all of them came within a 3 per cent tolerance, some of them high and some of them low, which obviously would have skewed our results had we relied on them. And if it weren’t for the GPS we wouldn’t have that fancy map to show you our driving route.
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