HPLX.NET REVIEWS Delorme Tripmate GPS Receiver
The Delorme Tripmate is a low-cost GPS receiver that comes bundled with Street Atlas USA 4.0. Since SAU4 is only useful on a Windows 95 machine, we can ignore it for this review and concentrate on the Tripmate itself. (If you live in the United States and have a Windows 95 desktop or laptop machine, though, it's a great program, with street level maps of the entire USA.)
A GPS receiver for the 200LX might seem to be a foolish idea-- after all, what good is it going to do with a lousy CGA screen and such a slow processor? Well, as it turns out, it can actually be quite beneficial. There are at least two good GPS programs that work with the 200LX. Both can be found at the S.U.P.E.R site. Since they are readily available to anybody, I won't be reviewing them here. However, since they are intricately tied in with the functionality of any GPS receiver being used with the 200LX, they will play a part in this review.
The Tripmate GPS unit is sold for about as rock-bottom a price as you can find. Plus, it's very small. It's only abut the size of two decks of cards stacked on top of each other. The unit runs off of four AA batteries, which are supposed to last about 15 hours. There's also an optional adapter for the cigarette lighter in your car. The unit is just one smooth yellow piece of plastic with a rubber gasket running around the middle of the side, and a long seial cable coming out from the bottom. There is no on/off switch; the unit is automatically activated by the DTR signal when you access it with one of the programs on your 200LX. (Note: this means that you must have a FULL SERIAL CABLE. If you have what I used to have, a cable made by using a CD-ROM audio cable for the 200LX side's pins 2, 3, and 5, OR ANY OTHER SERIAL CABLE THAT ONLY HAS TRANSMIT, RECEIVE, AND GROUND...it won't work. Believe me, I tried. I didn't want to pay $25 or so for the HP serial cable, or even $120 for the Connectivity Pack. But, since the makeshift cable didn't work, and the store I went to waited for TWO WEEKS without getting a plain cable in, I had to finally break down and get the Connectivity Pack. It turns out that it was a good idea, though, because not only is the Connectivity Pack's software useful for data conversions, it also includes a nice selection of adapters, one of which is a great 9-pin male to 9-pin male null-modem adapter that is a very nice solution to connect your HP serial cable to the Tripmate.) All in all, the Tripmate makes a nice complement to the 200LX because of its compact size.
How decent of a GPS receiver is the Tripmate? For GPS receivers, this question is usually measured by how accurately they can determine your position. Now, this is not just a function of the GPS itself. The US Department of Defense, which operates the satellites that are at the heart of the GPS system, employs a scrambling technique known as "Selective Availability" which constantly changes the reading on even the most advanced GPS receiver. It can vary by several hundred feet in any direction. Consequently, surveyors or other people who need to use GPS to precisely locate their position have to use other techniques, most of which are not feasible for real-time tracking. But most of the time, your GPS unit will be fairly accurate.
The Tripmate seems to do fairly well in field tests. It needs a clear view of the sky, especially when it starts up. Expect it to work considerably better when you're driving in the country than when you're driving down a city street with skyscrapers towering all around you. It usually takes about three minutes to initialize if it has a clear view of the sky. LXGPS has an interactive display that lets you see which satellites it has acquired so far. It needs at least 3 to determine your latitude and longitude. Both LXGPS and GPSCGA allow you to create and view maps with your current position displayed as a flashing dot (or other marker) on it. In tests I did, and with properly calibrated map files, the my pointer rarely strayed more than 15-20 feet from the my true position.
However, it was often difficult to get a lock on my position initially. The Tripmate has no external antenna, so unless you have a clear view of the sky, it won't be able to pick up the signal very well. Once I got the lock, however, it seemed to function fairly well.
If you plan to be using your GPS receiver mostly in an area without tall buildings and you have a clear view of the sky, the Tripmate is an excellent low-cost GPS unit. Otherwise, you might want to invest in a more expensive unit with a better antenna.
Copyright 1999, David Sargeant.
Last Updated 1-2-1999