Smartphones have all but replaced standalone GPS units for basic car and foot navigation in cities and on highways, but without apps like the ViewRanger, they aren't equipped to guide you around forests, mountains and trails. The new Trimble TopoCharger brings another such app, along with a full set of topographical maps and a full-sized back-up battery. Pop this case on, and the iPhone transforms into an outdoor GPS.

Designed to make it that much easier to use your iPhone as an outdoor mapping GPS device, the TopoCharger from Trimble Outdoors packs a full set of color topographical maps for 49 US states with 15 zoom levels, from 1:250K to 1:24K. An accompanying app works with the maps to guide you through the wilderness.

The map set is stored in a removable chip on the bottom of the TopoCharger case, the idea being that you buy a case for your home state, or wherever you adventure the most. You can then purchase other statewide map cards as needed and swap out the chips. Instead of just offering the maps in card form, the way other outdoor GPS products are packaged, the TopoCharger case includes a 1,440 mAh auxiliary battery that is claimed to double the iPhone's battery life.

The 3-oz (85-g) TopoCharger case is designed for the iPhone 4, 4S and 5 models. It will launch in November for a retail price of US$149. Versions for larger states, such as Texas and California, will cost $169.

Android users don't get the benefit of a streamlined case, but they can access the same maps with Trimble's plug-and-play SD and microSD cards, available for all US states except Alaska. Like the iPhone version, an accompanying app provides navigation functions.

Source: Trimble Outdoors