• GPS - Acronym stands for Global Positioning Satellite system. This is a system of low earth orbit satellites that circle the earth and send timing information to receivers on earth's surface. From the timing information sent by the satellites, the receiver can triangulate or "fix" its position on the earth. Our GPS receiver is a standard unit which can be bought in any sporting goods store. From our experience with this unit, we would estimate that it can fix its position with an accuracy of about 10 to 15 meters. This is based on static tests and on experience fitting location points to maps.

   

• Power Density - The amount of electromagnetic power flowing through an area. It has units of watts per square meter, so you can think of it as the number of watts of electromagnetic power flowing through a 1 meter by 1 meter square "window". Of course, in our maps we always present the power density relative to the safety code limits to make it easier to grasp the significance of the data (especially if you have no clue what 1 watt per square meter really means in the scheme of things).

   

• magnetron - an electron tube or vacuum tube which is capable of generating large amounts of microwave power. Microwave ovens use this type of tube as the generator of microwave power because they are cheap to build, relatively efficient and can easily generate hundreds of watts of microwave power. Typically, the frequency that they operate is 2450 MHz which is a frequency set aside for industrial, scientific and medical applications (this is why it is known as one of the ISM frequency bands). Some people believe that 2450 MHz is a special frequency where the absorption of microwave energy by water is optimum. However, if you look at the dielectric data for water, you will see that the coefficient which determines the amount of energy dissipation in water peaks at a somewhat higher frequency. In addition, the net amount of energy absorbed by a mass of water is also dependent on the size of the container in relation to the wavelength of the incident energy. So in reality there is nothing special about 2450 MHz.