Barometric altitude is a way of measuring altitude by using atmospheric pressure. As altitude increases, air pressure decreases, and conventional barometric altimeters measure the air pressure and convert it to an altitude using a model. This method is widely used in general aviation aircraft and is considered reliable. However, barometric altitude measurement relies on a "standard" atmospheric model, and there are many factors that affect atmospheric pressure, such as local weather conditions. As a result, a barometric altitude measurement rarely agrees perfectly with a geometric measurement. Geometric altitude measurement, on the other hand, is typically performed using GPS and tells you exactly how far you are from the ground. In practice, making geometric altitude measurements requires specialized electronic equipment like a GPS. The bottom line is that geometric and barometric measurements have their own advantages and disadvantages, and the choice of which to use depends on the specific application.