Global Positioning System satellites transmit signals to equipment on the ground. GPS receivers passively receive satellite signals; they do not transmit. GPS receivers require an unobstructed view of the sky, so they are used only outdoors and they often do not perform well within forested areas or near tall buildings. GPS operations depend on a very accurate time reference, which is provided by atomic clocks at the U.S. Naval Observatory. Each GPS satellite has atomic clocks on board.

Dear Weather Guy,

How do barometers work? Why do meteorologists use barometers? What do barometers do? When were barometers first invented? How do you make a model of a barometer? How accurate are barometers?

We recently found this article with a fantastic animation clearly showing the difference between spring and neep tides. You can find the original website here: http://www.sfgate.com/getoutside/1996/jun/tides.html

This article comes from Point 65N Kayaks from Sweden.

Gel-coat is the material which is used to create the glossy colored finish on the hull and deck. It is also the first material that is applied to the form, when building the kayak. Apart from generating the beautiful glossy finish on the kayak, the gel-coat’s function is to protect the fiberglass laminate - the boat’s main material – from moisture.