How accurate is a barometer for altitude?

With proper calibration, the barometric altimeter of an outdoor watch or handheld will report elevation readings ranging from -2,000 to 30,000 feet with an accuracy of +/-50 feet. Elevation values greater than 30,000 feet can be generated, but may not be accurate due to environmental factors.

How does a barometer measure altitude?

Measuring a Building’s Height With a Barometer

1. Measure the height of the barometer and then stand it next to the building when the sun is about 45 degrees in the sky.
2. Drop the barometer off the top of the building, measure how long it takes to hit the ground, and use this value to calculate the height of the building.

How do barometers measure air pressure?

The barometer works by balancing the weight of mercury in the glass tube against the atmospheric pressure, much like a set of scales. Once the two have stopped moving and are balanced, the pressure is recorded by “reading” the value at the mercury’s height in the vertical column.

Are iPhone barometers accurate?

According to online reports, the iPhone6 has a Bosch BMP280 sensor (see image), with fairly good numbers: absolute accuracy of +-1 hPa and relative accuracy for pressure changes of +-. 1 hPa (normal sea level pressure is roughly 1013 hPa).

How do they measure altitude?

An altimeter is a device that measures altitude—a location’s distance above sea level. Most altimeters are barometric, meaning they measure altitude by calculating the location’s air pressure. Air pressure decreases as altitude increases.

How do they calculate altitude?

In fact, aviators and mountaineers can measure their altitude by measuring the air pressure around them. This is called indicated altitude, and is measured by an instrument called an altimeter. As altitude rises, air pressure drops. In other words, if the indicated altitude is high, the air pressure is low.

How do you calculate pressure altitude?

To calculate pressure altitude without the use of an altimeter, subject approximately 1 inch of mercury for every 1,000-foot increase in altitude from sea level. For example, if the current local altimeter setting at a 4,000-foot elevation is 30.42, the pressure altitude would be 3,500 feet: 30.42 – 29.92 = 0.50 in.