Travelers use GPS map for accurate guidance
- By John McCormick
- May 12, 1997
They can always stop and ask for directions, assuming they find someone who gives
coherent directions. But what do they do in remote areas or halfway between interstate
exits? What if they're investigating a disaster area where road signs have burned or
The answer just might be DeLorme's Tripmate global positioning and map system, and it
won't even cost very much if your employees already travel with notebook computers.
Military users are familiar with handheld Global Positioning System units whose
readouts show map coordinates. However, that still leaves the user fumbling around with
road maps that may not have longitude and latitude grids.
What you really need out in the wild is an automated map that displays roads, streets
and site names, that finds locations by ZIP code and shows precisely where you
are-something paper maps can't do.
For Microsoft Windows-based notebook computers, you pay only $150 to get a computerized
map of every street in the United States as well as a simple satellite location system
that automatically plots your fixed or moving position on the map. The Tripmate GPS unit
is small, light and appears quite rugged.
This is perfect for most types of business travel. To get actual map coordinates,
switch to another mode and read off your position in degrees, minutes and hundredths of a
minute-even the altitude in feet, though this is less accurate. It could be vital,
however, for law enforcement or disaster relief personnel who must record precise
locations even when no substantial landmarks exist.
Civilian GPS units are supposed to be accurate to within 330 feet. Although I expected
to see some useful position information on the Tripmate maps, I didn't expect terrific
Imagine my surprise to find during my first test in rural Pennsylvania that the
accuracy was about the width of a two-lane road, or 30 feet. That was 10 times better than
After you install the Street Atlas U.S.A. CD-ROM, which contains named street data for
the entire United States, including streets in very small towns, you still have to
configure the GPS unit. This is a separate, doughnut-sized antenna and receiver that
operates on four AA batteries.
The 3- by 5- by 1.75-inch receiver plugs into a serial port on a notebook or desktop PC
running Windows 3.x or Windows 95. A six-foot cord is included. Configuration consists of
setting the COM port, if necessary, and specifying your approximate position. This needn't
be anything more detailed than what state you're in so the software can load the right
Because my fast 486 notebook had limited hard-drive room and I didn't want to carry a
portable CD-ROM player, I installed only the Pennsylvania maps. They took up about 50M on
the drive. Loading maps for several states probably wouldn't require as much as 50M each,
but that would depend on the states.
I carried the notebook and GPS outside to the hood of my truck and started the GPS
locator function. Within two minutes, Tripmate found several satellites and captured the
exact Greenwich time. In another minute, the map showed my location as a large green dot.
Expanding the map to maximum magnification, I saw that the locator had fixed my
position to within a few feet. As near as I could estimate, the location circle was about
15 feet across, and I was near the center of that circle.
With the notebook on the seat of the truck and the GPS antenna held up on the roof, I
saw the map start to indicate my direction of movement after I had driven about 10 feet.
Position updates continued as I drove down the road and back, about five miles in all. The
indicated location was only about 20 feet off my actual location at the end.
At some points during the drive, the indicated location was off by as much as 50 feet,
but at any location I found that I could stop and reset my position, and the accuracy
would go back to plus or minus 10 feet.
Doing exactly the same test on another day, I found that Tripmate's accuracy had
degraded to plus or minus 150 feet.
I couldn't identify any specific reason for this change, but at its worst, the unit
still performed at about double the guaranteed minimum accuracy.
The combination of the GPS unit and map software gives excellent location information
that should make navigation a snap even in unfamiliar neighborhoods.
I'll use it in my work as a local emergency management coordinator and state-certified
Pinpointing my location, even if only within a couple of hundred feet, lets me identify
which of several small streams I might be standing near.
That could be critically important, and I won't have to spend the usual time driving
back and forth to locate landmarks.
Tripmate could easily pay for itself by saving one executive or field team from getting
lost just once.
If you wanted to factory-equip a fleet of cars with a system like this it would cost
roughly $3,000 each, because each would require a built-in computer, in addition to a
John McCormick, a free-lance writer and computer consultant, has been working with
computers since the early 1960s.