A prototype wireless sensor network system for a comparative evaluation of differential and absolute barometric altimetry

Vertical distance measurements from height h to a reference position, as a variable independent of xy coordinates, can be attained from altitude measurements. Nowadays, the prevailing systems for determining altitude employ either a Global Positioning System (GPS) receiver or a barometric pressure sensor. The GPS altimeter receives coordinates from at least four satellites and calculates geometric altitude from the mean sea level (MSL). The barometric altimeter, on the other hand, measures the pressure applied by the weight of air molecules. Because ambient air pressure decreases at a standard rate as elevation increases, the altimeter determines changes in barometric altitude in reference to either the International Standard Atmosphere (ISA = 1023.25hPa at 15°C), or the local sea level pressure. Acquiring and subtracting altitudes of two distinct positions results in the vertical distance in-between them.