A small, handheld GPS shows the menu that allows the user to navigate. With just a few touches on the screen, the GPS menu will allow you to program your destination.
A close-up photograph of a hand holding a PDA, which displays its GPS feature. In addition to allowing you to make phone calls, schedule appointments, and send emails, many PDAs now have GPS features that allow you access maps and directions.
Atomic clocks operate by using the vibration of cesium or rubidium atoms to set very precise time, and are the standard in timekeeping as they are the most accurate clocks available.