Editor's note: Amy Gahran writes about mobile tech for CNN.com. She is a San Francisco Bay Area writer and media consultant whose blog, Contentious.com, explores how people communicate in the online age.
(CNN) -- Will smartphones replace personal navigation devices?
Over the last decade, dedicated GPS units (from brands such as Garmin and TomTom), which provide turn-by-turn driving directions, have become quite popular with motorists.
But according to new research from Berg Insight (an analyst firm based in Sweden), that era may be drawing to an close, as more people come to rely on their GPS-enabled phones for navigation.
"Global shipments of Personal Navigation Devices (PNDs) will peak at about 42 million units in 2011 and gradually decline thereafter," said Berg. "In mature markets where the installed base of PNDs is already high, the device category is facing increasing competition from smartphones and low-cost in-dash navigation systems."
These days, smartphones generally do offer turn-by-turn navigation comparable to that of dedicated GPS navigation devices. This functionality -- with audio prompts -- is built into Google Maps for Android. (Apparently there's a Garmin app coming for Android, but only on phones made by ASUS, Engadget recently reported.)
Also, more and more new cars come equipped with GPS-enabled navigation and communication systems, such as Ford Sync.
I've used voice-activated, hands-free audio turn-by-turn navigation on my Droid Incredible while driving -- and it worked very well. It was appealing to do this with a device I already have, so I didn't have to buy or rent an additional device. But there are significant tradeoffs.
Currently there are several big disadvantages to relying on your cell phone for GPS-enabled turn-by-turn navigation, with real-time mapping and audio prompts: decreased battery life, and poor or glitchy performance in locations with weak or congested wireless network access.
Right now, battery life for most smartphones is abysmal under normal operating conditions. I know many users of many types of smartphones, and most of them get much less than a day of use out of a single full charge if they use features such as mapping, Web browsing, social media, or e-mail -- or if they have their screens turned up bright (which often must be done to view the screen in daylight).
You must activate GPS tracking on your phone in order to use turn-by-turn navigation -- and GPS is a huge battery drain. It takes a lot of power to pick up, maintain, and hand off signals with multiple satellites. Plus, whenever you pass through locations with weaker or congested connections to your wireless network, your phone has to work harder to maintain cell service and transfer data -- which also drains your battery faster.
So if you intend to use your smartphone or tablet for in-car navigation, it's probably smart to invest in a car charger. Otherwise, you may arrive at your destination with a nearly-dead phone -- or worse, lose your navigation en route.
Plus, on cell phones and tablets, the maps and prompts associated with GPS-enabled turn-by-turn navigation get downloaded as needed over the wireless network. If you're in a location with poor cell service, maps and directions may take a while to download, and perhaps fall behind your current location.
Also, if you're in a location with no cell service at all, your GPS will still function -- but you may appear as a point on a featureless gray field, since your phone won't be able to download the associated map. Dedicated GPS devices have a greater capacity to download and cache maps and prompts.
And then there are the safety risks associated with driving while trying to read a small map on your phone.
So for these reasons, I think it's unlikely that dedicated GPS-enabled navigation devices intended for automobile use will disappear entirely. This market will undoubtedly shrink substantially, and may turn to focus more on vehicle fleets than individual customers. Manufacturers have been trying to increase consumer appeal by adding new features, but this is probably a losing game.
It's like wristwatches: Although the advent of cell phones and other digital devices that include clocks and alarms has shrunk the market for wristwatches, that market is far from gone and probably will never vanish entirely. Earlier this year, blogger Adam McFarland analyzed wristwatch market trends and concluded:
"I do think there is a correlation between increased cell phone usage and decreased interest in watches, and that the increased cell usage is at least partially responsible for the decline. ... I also think that the only reason that interest in watches hasn't fallen completely off a cliff is that there is still demand for watches as a style accessory first and a time-telling device second."