The easy-to-use, water-resistant sensor calculates its position by measuring the distance between itself and three or more GPS satellites. Note that GPS positioning requires satellite visibility to work, thus it will only work reliably outdoors, and not in valleys between tall trees and buildings. GPS signals also rely on radio frequencies (RF), and therefore won't go through metal or water. The G1, which works with AA batteries, offers a battery life of up to 10 hours in warm conditions or up to 15 hours in low-power mode. The sensor also weighs a lightweight 2.82 ounces.
About Polar
The first EKG accurate wireless heart rate monitor was invented by Polar back in 1977 as a training tool for the Finnish National Cross Country Ski Team. The concept of "intensity training" by heart rate swept the athletic world in the eighties. By the 1990s, individuals were looking to heart rate monitors not only for performance training needs, but also for achieving everyday fitness goals. Today, the same concept of heart rate training is being used by world-class athletes as well as everyday people trying to lose weight. Polar is the leading brand among consumers, coaches, and personal trainers worldwide and the company is committed to not only producing the best products, but also being the leading educator on the benefits of heart rate based exercise.