<span>February 29 is a date that usually occurs every four years, and is called a leap day. This day is added to the calender in leap years as a measure, because the earth doesnt orbit around the sun in exactly 365 days (1 year). The gregorian calendar is a modification of the julian calender first used by the romans. </span>
The unit of pressure is defined as 1013.25Millibars. This pressure is taken as the mean sea level. Expressed as the weight of air.
Altimeter Is a device used to shoe air pressure, the distance of a point above the sea level. They are commonly used in navigation purposes and most types of altimeters are barometric.
As the density of the air is lower at the higher altitudes. As the air is usually thinner at the higher altitudes. The GPS, for instance, can also provide an altimeter and used by skydivers.
