Hello, I want to calculate the world magnetic field size in my region with ESP32 and Pololu LIS3MDL module. This value is displayed in one corner of the compass programs used in smartphones. For example, in my region, these values are; It is displayed in the range of 46ut - 48ut.
However, when I look at magnetic detection sensors, these values are mostly formulated as x, y, z values in very different sizes.
I'm asking because I don't know, how can I get micro tesla size values like 46, 47, 48?
Do you mean calculate or do you actually want to measure it?
The LIS3MDL will allow you to measure it in three dimensions, it is known as the magnet field vector. It shows you the direction of magnetic field where you are with reference to the sensor.
What are you going to do with this information? It will change when the angle of the sensor changes or when it is in the presence of another local magnet.
This is what I did with a magnetic sensor
I don't want to measure the direction of the magnetic field. What I want to reflect on the screen; values in micro tesla, just like 46, 47, 48 mikrotesla, which I see in compass applications on mobile phones. I want to know how I can do this.
Sorry I don’t know. However I would take a guess that it first determines your location via GPS and looks up the numbers from a web site that gives the information for your location, and then displays that on the screen.
Something easy to do on the phone where you have both GPS and an internet connection but somewhat more difficult for you Arduino as you would have to fit a GPS module and have internet access through wi-fi or a phone connection.
The datasheet for the device will specify the sensitivity, and how the size of those values relates to physical units.
The earth's magnetic field is parallel to the earth's surface on many parts on the globe, with only a small vertical component. The closer you get to the magnetic poles, the larger the vertical component gets. At the poles, it's completely vertical, which is why a traditional mechanical compass won't work there in the normal way.
The Polulu sensor, and the sensor in your smartphone, measure the field in 3 dimensions. It measures the field in 3 components, X, Y and Z, relative to the sensor chip itself. So if you mount/orientate your Polulu sensor horizontally, you can simply ignore the vertical component and read the 2 horizontal components to get the values you want. In a smartphone, the phone might be held at any angle, so software in the phone will need to use an accelerometer to measure the orientation of the phone and transform the 3 components to compensate for the phone not being held horizontally.
Hi,
The 3 axes give you what is called a vector, the direction and length.
The length or magnitude is calculated by
The square-root of the sum of the squares.
Tom... 
So, is lABl the value of the magnitude I'm looking for?
Please note other members that the OP said
So I am not at all sure why he wants to use a magnetic field sensor.
It is apparent now he doesn’t know what “vector” means, which is maybe why he ignored my first reply.
So I think there should be a formula for this. the mobile phone does not get these values from anywhere else with the gps method. Because, at the same time, any material that creates a magnetic field is instantly affected.
So why did you say you did not want to measure the direction of the magnetic field?
I may have misunderstood. I said I wanted to measure the magnetic field. Not north direction. So, I don't want a compass. A compass shows the direction of the Earth's magnetic field. Maybe I can think about that too. However, what I really want is to be able to measure the instantaneous earth magnetic field size in my area.
No you didn’t stop making things up.
Yes..
If you want direction, that is a bit more maths.
Tom..
You're so grumpy Mike :))
Look, I agree with you. I couldn't evaluate your first answer because I don't know, my friend. I could not understand the connection between the concept of direction and the concept of size.
However, I'm not making it up, believe me, I'm just trying to learn.
This answer has been great. Thank you. :slight_smile 
So take note of the answer that @PaulRB gave. You will need that in order to make your application sensor position invariant.
To be more precise, are you looking for the magnetic field strength at a particular location, or the field size (which extends far into space around the planet, and is affected by external factors such as the solar wind).
Yes, this is what I want; magnetic field strength at a particular location. I think these are the values ​​such as 47, 48 or 50 micro tesla in the compass application on phones.
I sincerely thank all my friends who helped by replying. I have solved an important problem.
