GPS navigation devices can help guide you on confusing freeways and country roads, but generally do not work indoors. But Navman, a maker of GPS navigation devices and modules, claims that its new Jupiter 30 GPS module that is sensitive enough to pick up signals in canyons, parking garages and even indoors.

The module can either be a standalone device or embedded into third party GPS navigation systems. Capable of detecting signals as weak as -159 dBM, the Jupiter 30 brings GPS tracking to previously "impossible locations," Navman said.

The Jupiter 30 is about the size of a Compact Flash memory card, is only one-tenth of an inch thick and weighs four grams. It can track up to 20 GPS satellites simultaneously (out of a 24 total) and Navman says that horizontal positioning is within 9.5 feet. In addition, velocities of up to 500 meters per second and acceleration of up to 5g can be tracked.

Everyone who has used a GPS device before knows that it takes time for the receiver to get the first reading ; this time is known as the Time to the First Fix (TTFF). The TTFF for the Jupiter 30 ranges from less than a second for a hot start to 66 seconds on a cold start (device is powered up with no previous readings in memory).

Some people claim to have already picked up GPS signals indoors with other devices. Some of the more sensitive GPS devices can natively pick up a signal indoors, if users are standing close enough to a window. In addition, GPS signal repeaters have been sold for several years on the Internet. These devices allow GPS tracking devices to work indoors, but are primarily used for systems testing, rather than full bore navigation.

Navman said it will be starting full-scale production of the module this month.