Choosing a GPS for your RV
Dave and Helen Damouth www.damouth.com
18 March 2002
Before choosing a brand and model of GPS, you need to first decide what you want to do with it. If it will be used only in the RV and only with a computer, you might as well get the simplest and cheapest - The DeLorme Earthmate. It works about as well as any. List price is $190 for a package which includes the GPS receiver and the Street Atlas mapping product. Discounted Internet price around $138. Caution - Earthmate is not guaranteed to work with mapping products other than those from DeLorme (Street Atlas, Map'n'Go, etc). If you want to use it with mapping products from other manufacturers, check compatibility before buying.
But many of us also want to use our GPS by itself (without the computer), when we go hiking or biking or boating or flying. For this, you need a GPS receiver with a built-in display and control buttons, which costs more. These small self-contained hand-held units work just fine with the computer, but also can be used by themselves, powered by internal batteries. Caution - the smallest and cheapest of the hand held units do not have the connector which allows them to be plugged into your computer - make sure this feature is included.
Another nice feature of some of the hand-helds (not available on the Earthmate) is a connector for an external antenna. In some motorhomes, particularly metal-framed or metal-skinned Class C rigs, simply placing the GPS receiver (with its built-in antenna) on the dashboard won't work. The overhead structure of the RV blocks the radio signals from the satellites. In this case, it's nice to be able to attach a small weatherproof antenna to the roof of the rig. (Some people have reported success in mounting the entire Earthmate unit on the roof (or inside, under a plastic vent), and some have even successfully cut and spliced an extension into the cable from Earthmate to computer when it wasn't long enough.)
Although there are many brands of GPS available now, I'd recommend buying either Garmin or Magellan units. Both companies have been in the GPS business from the beginning and have progressively refined their products. Each has several models differing in price and in the particular set of features included. (basic GPS performance is about the same for all of them).
We use a Garmin 12XL hand-held GPS receiver, usually on the dash of our tow vehicle, plugged into our laptop, which sits on the center console between driver and navigator. This GPS fits in my pocket when I'm hiking, has computer and external antenna plugs, and has fairly good battery life in the field (about 20 hours of on-time). Current price from Internet dealers is around $230. Last time I looked, there was a couple of used ones available on EBay for $50 and $128, both in "perfect" condition.
One caution in buying a used 12XL. The earliest versions (built in early 1997) are not quite the same as the new ones. I have this early one. It has only about 10 hours of battery life, and also has a bug which results in slowly discharging the internal batteries if you leave it plugged into external power. There are also several other minor performance improvements in the newer ones. New software releases have happened occasionally and if you buy a used unit, you'll want to check the Garmin website to see if a software upgrade is available for your particular unit (identified by serial number). With a used unit, you'll have to separately buy the current version of Street Atlas or another mapping product. Unlike the Earthmate, Garmin and Magellan have an industry-standard computer interface which should work with *any* mapping product that has GPS input.
One nice thing about the 12XL is that it can be powered directly from your vehicles 12v. power, via the cigarette lighter or other connection. It runs on any DC power from 10 V. to 40 V. For custom installations, Garmin will sell you a cable with bare wires at the power and computer ends, allowing you to choose your own type of connectors. I don't like the "cigarette lighter" type of plug, and have my GPS and laptop power supply wired directly to the vehicle's power through small plastic connectors from Radio Shack, which are neater and more reliable.
There are several similar models from Garmin and Magellan which have essentially the same performance, but have variations in user interface to fit individual needs and preferences. More expensive models with larger, higher resolution color displays are available with built-in maps. I find the built-in maps to have such low resolution and detail that they are nearly useless for either hiking or RVing. For use in a vehicle, I find the large high-resolution laptop computer map to be very important. For wilderness off-trail hiking or canoeing, I carry the standard paper 7.5 minute USGS topographic map for the area I'm in.
With any of these products, you'll have to buy a cable and/or power adapter which connects to your vehicle's cigarette lighter (for power - batteries don't last long enough) and/or to the computer. For Garmin, it's around $40. For Earthmate, the computer connection is included and the separate power adapter is about $25.
One caution: Most of these GPS products connect to the computer via the RS-232 serial port, using a DB-9 (nine-pin) connector. Some new laptop computers no longer have a serial port, which will force you to spend $25 or so on a converter from a USB port on your laptop to a serial plug on the GPS (these are available from numerous computer equipment suppliers on the World Wide Web). These USB converters are not a simple passive adapter. They require installing a software driver (provided) on your computer.
DeLorme offers a serial-to-USB adapter on their website for $49.99 (and says it works only with the Earthmate). It's worth the extra cost because it also provides power to the Earthmate so that no separate power adapter is needed. (Unlike serial ports, USB ports are designed to provide power to external devices, although this only works with very low powered devices like a GPS)