Hack 48. Accessorize Your GPS

Get more enjoyment out of your GPS by making and buying simple accessories.

The heart of a GPS receiver is pretty simple: a small box of electronics that does magic. In the introduction to this chapter, we learned a bit about the features of a GPS receiver that contribute to buying decisions. Now let's go wild and discuss accessories!

5.4.1. Waterproof Floating Cases

Typical GPS units are rated as waterproof to one foot. While I'm sure this is true for the new, just-off-the-shelf unit, I know for a fact that this is less true if the GPS receiver is three years old and subject to a harsh Channel Islands crossing on an open boat. In addition, your GPS receiver is certainly not waterproof at the depths to which it will surely plunge when it manages to escape the bounds of your boat. On a recent dive trip, I came upon a small pile of gear that had obviously fallen off the back of a boat: a single fin, dive knife, and a watch. I stashed the loot in my lobster bag, but first looked at the watch. "Darn," I thought. "Is that really the time? There is no way I'm going to be able to get another dive in before the night dive."

I was able to make use of the knife and the watch, but if there had been a GPS in the pile, I would have cried over the waste of now-ruined technology. Fortunately there is a simple answer: a floating waterproof bag. See http://www.waterproofcases.net for a line of waterproof cases that start at $24.99. Or do a Google search for "GPS case" and scan the 9,140 results.

5.4.2. Mounting the GPS

Handheld GPSes are nice in your hand but leave a bit to be desired when you try to add them to your bicycle, motorcycle, automobile, or Burning Man art car. In these cases, you need a GPS mount. Fortunately there are a lot of options.

For years, I have had a strip of Velcro on the bottom of my GPS and Velcro pads on each side of the front of my cars. Driver or passenger, I'm never far from my personal digital carrier pigeon.

A less useful technique with the Garmin Rino is to string a strip of Velcro through the small hole between the antennas, wrap that around your steering wheel, and Velcro it shut. This appears to work for long periods, but when the Velcro loosens, as it will when you turn a corner, the GPS will flop down into your lap, causing you to experience great driving difficulty and almost run into a parked car.

Trust me on this one. Velcroing the GPS to your steering wheel seems like a good idea, since it keeps the GPS handy right at a spot where you can easily look. But this turns out to be a bad idea. Fortunately the GPS industry has responded to the crowds of folks with electronics flopping in their laps with a wealth of GPS mounting options.

RAM Mounts at http://www.cycoactive.com/gps/gps_mounts.html has the coolest-looking mounts for motorcycles and bicycles. They are made from stainless steel and come with shock mounts and places to route the power cable. I have to agree with their site: "beautiful construction, looks like it was made in a robotics laboratory."

The folks at RAM Mounts also have a great page discussing the problems of operating a GPS under extreme vibration (http://www.cycoactive.com/gps/gps_batteries.html).

5.4.3. Batteries?

Rechargeable Nickel Metal Hybrid batteries are the best choice for digital cameras, but they don't seem to match the power curve of GPS units as well. Still, if you don't mind swapping batteries during a trip, NiMH batteries are great. I've done battery-life comparisons with three different units that used 2, 3, and 4 AA batteries. In all cases, I get around 18 hours on Alkaline batteries and closer to 12 hours on NiMH cells.

5.4.4. External Antennas

Some GPS units will let you attach an external antenna. This can boost your reception substantially, especially if you're working with the device inside a vehicle or another signal-reducing area. Even if you have an antenna permanently mounted, if you started with a handheld GPS, you'll be able to occasionally remove the GPS to walk around: just free the GPS, disconnect the antenna, and you're off. Antennas seem to start around $30 and go up from there, depending on the application. (If you're feeling adventurous and want to build your own antenna, see http://www.arrl.org/tis/info/pdf/0210036.pdf for one set of plans.)

5.4.5. Power and Data Cables

GPS units go through batteries quickly. If you are using your GPS in your car, you can use a car cigarette-lighter adapter. Perhaps you want to track your location to a GPS tracklog logger or a laptop at the same time you want to power the GPS from the car. You can do so with a combined PC interface and cigarette-lighter adapter.

The GPS vendors are happy to sell cables. A PC interface cable or cigarette-lighter adapter for the Garmin Rino is just under $40. The combined cable? $50 even.

5.4.6. Make Your Own Garmin Data Cable

Larry Berg bought a Garmin GPS-45 and wanted to connect it to his computer. For some odd reason, the Garmin used a proprietary cable, and Larry didn't want to pay $30 for a connector and a bit of wire. (The full story is at http://pfranc.com/projects/g45contr/g45story.htm.) In 1996, he made his own mold and ended up with extra connectors, which he offered for free. The power of the Net took off, and now he is the head of a worldwide network of "pfrancs." You can offer a pledge to your local pfranc, and they will send you two connectors for free.

If you like the connectors, you honor your pledge, and the worldwide network of good feeling continues. They also have a serial-to-USB adapter, essential for getting your tracklogs when all you have are USB ports [Hack #50] .

Get inspired, get involved, and check out http://pfranc.com for your GPS accessory needs.

5.4.7. Maps

Many GPS units allow you to upload maps. Garmin has its MapSource product line, with CDs of detailed maps covering everything from marine charts to topo maps. Check out the Garmin Cartography page: http://www.garmin.com/cartography. And if you don't see a map for the area you want, see [Hack #54] to learn how to hack your own maps for Garmin GPS devices. There are also lots of vendors in this space worth exploring.

Bottom line? There is always another gadget or accessory to add to your hobby!