What is Altimeter – A Sensor That You Should Know

You might have read my post on the barometer sensor if not I recommend you to go and read it. Similar to it there is another sensor called the altimeter sensor that presents us the altitude of our current location.

Today, there is no such smartwatch without an Altimeter Sensor.

So, let’s begin our walk towards exploring the details of this sensor.

Let’s See It’s Definition

An altimeter is an instrument which is used to measure the height of an object with respect to a fixed reference. As altitude can be interchangeably used with height, the instrument is called an altimeter.

Moreover, this measure of altitude is called altimetry. You can create a link between the bathymetry, depth underwater, for a better understanding of it.

Now you know why they are called altimeter, but more specifically they are called pressure altimeter. Deeper in the post we will see how it functions but before that it is important to know why we use altimeters.

The Need Of Altimeter

Why do we need an altimeter? This question might come in your mind. Moreover, it is obvious for such questions to come. We don’t seem to bother at what altitude we are on a daily basis.

But being aware of the altitude is important in many fields of study. Let us take the example of an airplane. Does the pilot prioritize knowing the height of the flight?

Yes, buddy if he doesn’t then it would have been difficult for one to survive a flight. Because there are tall buildings and along with your airplane there are other airplanes too wandering the sky day & night.

Therefore, for safe transportation knowing the altitude of flight is very important. Similarly, the calculation of the altitude of lands with the fixed point as sea also is keen for research & other fields of study.

Okay so, altitude measure is important but how it is measured? Few of the many ways in which you can measure altitude –

  • With the help of Pressure
  • With the help of Radio Waves
  • Using GPS [Global Positioning System]

In this post, we will discuss the traditional techniques of measuring altitude i.e –

  • Using Pressure
  • Using Radio Waves

Working Of Altimeter

Before moving further discussing the details, I have one question for you. Which techniques are widely used and why? So, if your answer was traditional techniques then you are right.

Moreover, the reason behind this is accuracy. Traditional techniques are good at giving high accuracy measures.

Pressure Altimeter

I hope you are well aware that pressure varies with height. So, what is the general trend? As the height increases the pressure decreases. Therefore, remember, the pressure is inversely proportional to altitude.

If you know about Fluid Dynamics then you can relate this with how pressure plays there with altitude. This is the reason why Pressure Altimeter is also known as Barometric Altimeter.

Now let’s see its working –


Image result for Altimeter works

Image credits – AviationKnowledge


These instruments consist of a box which is hollow & sealed so that the inside pressure of the box is preserved. Therefore, the shape of the box changes through contraction and expansions as the outside pressure rises and decreases respectively.

Furthermore, this instrument is called the Aneroid Barometers, pressure measuring instrument. So, as this is a pressure measuring instrument, how it measures altitude?

As we discussed there exists a relation between pressure and altitude. Therefore, the instrument reads in pressure but the output displayed to the user is in altitude.

This is possible because the Barometer internally scales the reading to give the output in terms of altitude. Therefore, this method of measuring altitude is very accurate.

Radio Altimeters

Radio Altimeters are better and preferred over Pressure Altimeter. So, before discussing Radio Altimeter let’s first see what are the drawbacks of Pressure Altimeter that Radio Altimeter passes.

Drawbacks of Pressure Altimeter

  • Change in weather conditions gives rise to constant fluctuation in air pressure. Therefore, the accuracy is at stake.
  • The Pressure Altimeter fails to inform about obstacle such as buildings etc.

So, Radio Altimeter overcomes these drawbacks. Moreover, their working is even simpler. Have you ever heard of RADAR, the technique ships use to locate the depth of the sea? The same idea is used here, a radio wave is fired towards the ground from the airplane via a transmitter.

This signal is received again by the airplane through a receiver after it has reflected from the ground. We know that radio waves have a travel speed same as of light.

Therefore, it will take no time to complete the process of transmitting and receiving the signal. The below diagram will help you to understand the scenario.


Radio Altimeter


The time taken for the waves to travel the path is recorded. Now if you can recall how distance is calculated using speed and time then you have got the whole concept.

If you cannot recall then just see the below diagram to understand that too.


Altimeter Radio Waves

Altimeter in Smartwatches

Well, the smartwatches that we use today daily, all have altimeter sensor in it. Similar to other sensors used in Smartwatches an altimeter is also a feature that manufacturers provide you with.

Hence, when you go for trekking, skydiving the altimeter of your Smartwatches provides you with the details of the altitude you are currently at. Moreover, the altimeter of the Smartwatches uses GPS to locate the altitude. Also, there are Smartwatches using traditional height measuring approaches.


Here was everything you need to know about altimeter as a beginner. One more thing, if you need an app for your smartphone to monitor the altitude details then you can check the My Altitude App, both for iOS and Android.

So, I believe you enjoyed this piece of information and share this with your friends and family.

Thank You For Reading…

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