Loading GPS maps

For the directionally challenged, there is help. No longer do you have to listen to your companion belittle your abilities as a navigator or swallow your pride by admitting that you're lost. Today's in-car navigation devices are just the thing to keep you on track during your travels, and they're ready for prime time. In this guide, we discuss the technology behind GPS and tell you what to look for when you're ready to make the purchase.

Virtually all vehicle GPS systems come with maps, although not all of them are detailed street-level maps. Most in-dash models use optical media, such as CD-ROM or DVD-ROM discs that come directly from the manufacturer with maps preloaded. In some cases, these discs are part of the package, but some vendors require that you purchase them separately or subscribe to a plan that provides updated discs on an annual basis. DVD media containing detailed maps of the entire United States are typically priced in the $300 range.

Top-of-the-line portable models provide comprehensive street-level maps on a hard drive, so you never have to worry about losing detailed coverage when you travel outside of a map region. This seamless coverage is what makes this type of GPS system so popular. Units that use removable media, such as flash memory cards, can hold as much detail as the memory card allows. For example, the Mio 136, a PDA/GPS device designed for use in a car and on foot, doesn't come with preloaded maps. Instead, it has 32MB of internal memory and comes with a 256MB SD (Secure Digital) card to hold detailed map regions. A typical map region, such as the Boston to Washington D.C. I-95 corridor, uses over 200MB of storage. If you want to cover more ground, you'll have to purchase extra SD cards and preload the necessary regions before hitting the highway. Changing SD cards on the fly is no big deal, but it can get expensive if you want nationwide coverage at your fingertips.

The least expensive units will come with base maps of the United States, which include major interstate roadways and highways. For some travelers, this is sufficient, especially if they simply want to track their progress on long-range trips. If the unit has enough memory or a slot that accepts flash media, you can add detailed maps as you go. It's rare to find an automotive GPS system that relies on internal memory to store maps since flash memory offers more flexibility.

Loading maps onto your GPS unit can be a time consuming process. First, you'll have to load the mapping software on a PC and connect the GPS device to your computer. Depending on the software, you can select pre-determined regions to upload, or you may have to pan the map and create your own regions, which requires constant adjustments to create a region that will fit on your memory card. In some cases, you have to visit the vendor's Web site to download maps to your PC, and then upload them to the GPS unit. Both methods may require an unlock code to access the maps, which usually carries an additional fee and can cost hundreds of dollars depending on the vendor.

More GPS resources from CNET