According to the principle of air pressure altitude measurement, the paper introduces the composition and the working principle of digital measuring system, and it discusses the circuit design of every part of the measuring system and flow chart of program design .

The method to measure the barometric height for UAV(Unmanned Aerial Vehicle) is proposed,in which the barometric height is calibrated by GPS(Global Position System) height and is compensated by atmosphere temperature.

After a series of theoretical analysis and statistic reckoning,the results show that the geometric altitude may be several hundreds of feet and even much lower than the pressure altitude because the actual air temperature is well below the standard air temperature in winter.