When you get out of the city, the usual thing like a smartphone no longer helps. You need a reliable device that helps you navigate in space (and sometimes in time), as well as obtain other important information. Moreover, the device should be as light as possible, compact and, for that matter, multifunctional. This digital compass is just that. With it (and with charged batteries in stock) you will not get lost, you will accurately determine the point where you are, which means you will understand where to move on.

The device weighs much less than 100 grams, fits comfortably and easily in the hand, has several built-in sensors, an LCD display and the ability to save the history of the last recorded data (up to 8 positions). A convenient lanyard for hanging around the neck and an LED element for lighting up in the dark complete the basic features to a comfortable level.

Built-in features:

1. watch;
2. calendar;
3. thermometer;
4. barometer;
5. altimeter;
6. compass;
7. weather sensor.

And all together makes it possible not only to determine the coordinates of your location, but also to lay the right course to your destination.

Clock and calendar

With these counters, understandable even to children, everything is simple. Once set the correct date and time and track the current moment. You can select 12-hour or 24-hour time display formats. Pressing the SET button allows you to move from time to date. And a long press of the SET button allows you to enter the settings mode, in which you can set the date / time, as well as select the usual units of measurement.

Thermometer

The temperature can be displayed in either Celsius or Fahrenheit. There are also several options for determining the state of the weather for the near future: clear, mostly cloudy, cloudy and precipitation. The information is updated every 30 seconds.

Barometer

The value of atmospheric pressure, as well as time with date and current temperature, is displayed on the display in standard mode. Information is updated every 30 seconds. If accurate data is needed, press and hold the SET and ALTI buttons. Atmospheric pressure can be displayed both in millimeters of mercury and in Hecto-Pascals.

Altimeter

Pressing the ALTI button switches to the mode of measuring absolute height (ABS). The data is updated every 5 seconds. Holding down the ALTI button puts you in Relative Height (REL) mode, which resets the reading to 0. Altitude can be measured in either meters or feet.

Compass

Pressing the COMP button allows you to switch to the compass mode. Holding the same button switches to its test mode. How to do this is described in detail in the accompanying instructions. Keep the compass away from magnetic fields when measuring direction. Distortion can occur due to other magnets in the vicinity, as well as due to iron and steel objects.

In general, with such a manual electronic assistant, you will not get lost. Once again, we remind you about the supply of batteries. Here, "little fingers" are used.

Gift for a traveler

Such a useful thing, of course, will be appreciated by those who like to go camping for a long time, especially in mountainous areas. And he can also use a pedometer and a 4 in 1 multitool. The multitool has a powerful flashlight, a night lamp, a fan and a music device (playing MP3 files and radio). During parking and in the dark it helps a lot.

Characteristics

• 7 in 1: clock, calendar, thermometer, weather sensor, compass, altimeter, barometer;
• instructions are attached;
• LCD display;
• backlight with LED signal for 5 seconds;
• saving and viewing the history of previous values;
• dimensions: 6.5 x 2.5 x 10 cm;
• weight: 85 g;
• data update period: 30 seconds;
• temperature range: -10°C to 50°C (14-122°F);
• altitude range: -305 m to 9,144 m (-1,000 to 30,000 ft);
• atmospheric pressure range: from 225 mm Hg to 788 mm Hg (301-1051 hPa);
• Runs on 2 AAA batteries (not included)
• there is a lace;
• brand: LeFutur;
• packaging: branded box;
• box dimensions: 7 x 11 x 3 cm.

Until recently in geodesy compasses and compasses were mainly used, where the sensitive element is a magnetized needle rotating on a rod and used in various modifications of these devices for several millennia. When orienting, the needle takes such a position that its plane becomes parallel to the lines of the magnetic field passing in this place. If the needle has two degrees of freedom, i.e., it can rotate in the horizontal and vertical planes, then the direction in which the needle points will show both the declination and the slope of the local geomagnetic field. In many devices, in order for the needle to accurately show the direction to the north magnetic pole, it is usually balanced specifically for the characteristics of the magnetic field of the region in which the compass will be operated.

Sometimes compasses with global balancing are used, which can be used all over the world. To dampen the vibrations of the needle during movement, the compass is filled with liquid (a mixture of water with alcohol or purified oil). The readings of such instruments are burdened with errors due to the influence of external influences such as vibration, tilt, acceleration, and external magnetic fields. Traditional compasses and compasses are difficult to adapt to digital reading, and therefore difficult to use in combination with the latest geodetic instruments.

In modern electronic compasses used as a sensing element magnetometers, which are, like the compass, analog instruments and measure the intensity of one or more components of the Earth's magnetic field at the point where it is located. The signals from the output of the magnetometer are converted into digital form and can be used for further processing by the microprocessor. In modern instruments, magnetometers are mainly used, which use magnetoresistive and magnetoinductive sensors, sensors based on the Hall effect, as well as sensors made using the "fluxgate" technology. For orientation, an electronic compass is usually used, which has two magnetometers mounted in a horizontal plane at right angles to each other in order to measure one of the B x or B y components of the magnetic field, respectively, along the x-axis or along the y-axis. The angle between the x-axis and the magnetic meridian will be:

ψ = arctg(B y / Bx). (7.1)

Modern magnetometers are small and built into integrated circuits.

Some geodetic instruments anisotropic magnetoresistive (AMP) sensors are built in, which are special resistors made of a thin permalloy film, the magnetization vector of which, when it enters an external magnetic field, begins to rotate or change angle, changing the resistance of the film. In measurements, such a film is placed in a Whitson bridge and the voltage change caused by the change in the resistance of the film is evaluated, according to which the strength of the magnetic field is estimated. Magnetoresistive sensors provide greater than one degree accuracy and can have one, two or three axes and are built into electronic compasses.

It should be noted that many satellite receivers have similar built-in electronic compasses. Satellite receivers usually use a two-axis compass, and in some cases, three-axis heading sensors, which allow you to get fairly accurate directions even in the case of a slight inclination. In the case when the satellite receiver is moving at a speed of over 10 km/h, it can determine the direction of its movement from satellite observations with an error of less than one degree. At lower speeds, a GPS receiver complete with one antenna is not able to determine the direction of movement. Therefore, the receiver is tuned so that when it reaches a certain speed (for example, 5 or 10 km per hour), it would switch from the compass heading function to the heading function obtained from satellite observations made by the GPS receiver itself, and when the movement speed decreases the receiver returned to the direction of the compass.

In order for the satellite receiver to be able to calculate both geographic (true) and magnetic azimuths of movement, software is embedded in the receiver that contains the parameters of the model of the main geomagnetic field of the Earth. The receiver continuously updates the object direction information as the user navigates an arbitrary path to the object.

Magnetic inductive direction sensors appeared relatively recently - the first patent for them was issued in 1989. The principle of its operation is based on the fact that the oscillation generator uses a coil, the inductance of which changes under the influence of changes in the surrounding magnetic field. A change in the inductance of the coil causes a change in the frequency of the generator. Thus, this type of magnetometer measures the magnetic field by its effect on the inductance of a coil of wire or solenoid.

To determine the direction to the north magnetic pole (in the horizontal plane), two such sensors, installed perpendicular to each other, are fixed on a gimbal so that they are located in a horizontal plane, and an inclinometer is also used in a three-axis one. Many modern automotive compasses are based on magnetic inductive sensors.

When you are going to hunt in an unfamiliar area where there are no visible landmarks, you must definitely take a compass with a map of the area with you. Such a precaution is needed in the steppe and tundra, in the mountains. You can not do without a compass on a dark night, on a foggy day and in a blizzard.

What are

A compass is a device with which you can navigate in unfamiliar terrain.

Compasses are:

• magnetic;
• liquid;
• electronic.

liquid

The most accurate among all magnetic is considered a liquid compass. In a typical simple version, it looks like a “cauldron” filled with water, in which an aluminum or bronze card is fixed on a vertical axis. There are magnets attached to each side of the card.

In such devices, the liquid stabilizes the pointer, in a stable position, the pointer helps to accurately determine the reading.

Tablet

Such a device is presented in the form of a tablet, a round bulb with a magnetized arrow is installed in it. Equipped with a tablet compass magnifying glass for easy viewing of the scale. A special liquid in the capsule ensures the stability of the arrow during fast movement.

Basic Models

Designed for beginner hikers, they have all the necessary components, but they do not have a mirror and deviation adjustment.

Multifunctional

They are equipped with a mirror, magnifying glass and other additional features. Suitable for regular hikes in the outback, away from the routes.

Magnetic

There are several types of devices with which you can determine the cardinal points.

Mechanical

It happens to be an ordinary tourist. This type of compass has a red-tipped needle that points north, where the strongest magnetic field is. With a simple magnetic device, together with a map, you can more accurately determine the location of various objects.

For the military

It differs from the usual magnifying lens and sighting device. With such a device, you can more accurately determine the direction of the path in the field.

Geological

In this instrument, the divisions of the direction scale are counterclockwise. To determine the angles of incidence of rock layers, it is equipped with a clinometer and a semi-limb.

Hygroscopic

The hygroscopic compass is installed on aircraft and on river ships. It is equipped with a gyroscope, thanks to such a device, it shows the true pole, and not the magnetic pole. This device is stable, so during the buildup it shows the direction more accurately.

Astronomical

This view can determine the cardinal points, focusing on the stars and luminaries. The disadvantage of the device is that you cannot work with it during the day.

For orienteering

Which compass should athletes choose? They should be able to use a magnetic compass and understand a topographic map.

Therefore, an orienteering compass must have high performance characteristics, such as:

• speed and speed of installation of the magnetic needle;
• the stability of the arrow during the rapid movement of athletes;
• ease of use, so that the device is held steady in the hand;
• small size and light weight.

Electronic compasses operate on the basis of magnified sensors, being included in the search for the desired coordinates in the satellite navigation system. They are intended only for professionals, they are used mainly by military personnel and representatives of law enforcement agencies.

Depending on the place and purpose, these types of electronic navigators are used.

Indicates the direction to an object emitting radio waves. It is used by aviators for orientation in space during flights.

It differs from the mechanical tourist one in that it does not have a magnetized needle. The compass determines the cardinal points electronically. It shows the time, various additional programs are built into it, even videos.

GPS and GLONASS

These navigators work with the help of an electronic system, they receive signals for determining the exact location and direction from several satellites.

GPS receivers are considered high quality navigators, almost always equipped with an electronic compass. But GPS-navigators cannot work without a battery, which can be discharged at the right time. Therefore, during the trip you can not do without a magnetic compass or a set of spare batteries.

GPS receivers, unlike magnetic compasses, have the following advantage: they can estimate the current location without visible landmarks on snowy days and in foggy weather. With a GPS device, you can easily set the desired direction when avoiding any obstacle and re-adjust the compass along the changed route line.

Criterias of choice

The choice of a compass depends on the purpose: they buy it for hunting, for hiking or orienteering. It is recommended to choose a compass model in such a way that it can be used in different situations: during hiking trips and orienteering competitions.

What is the best compass for hikers and bikers?

When choosing, you need to take note of some of the nuances:

• Classic models of compasses with degree division and with a ruler are suitable for hiking trips.
• Tourists often use degree calculations and azimuth calculations, so they need a ruler and a degree dial on the compass in a hike.
• For cyclists, a more acceptable option is a GPS navigator, although its batteries run out quickly. Therefore, cyclists will have to take a classic compass with them.
• For traveling by air, preference should be given to electronic navigators, since they are multifunctional, you can determine both altitude and pressure from them.

Overview of the best models

Good quality equipment for tourists is produced by the Swedish company Silva and the Finnish company Suunto.

Suitable for use on any terrain, it is a classic professional orienteering device, equipped with the Spectra system, the arrow of the device is straight and wide, convenient for quick readings.

Differs in such features:

1. With a strong magnet, the pointer of the device quickly calms down.
2. Transparent base plate with clear markings
3. Security placement in hand.
4. The Silva 6 Nor Spectra Right model can also be held in the right hand.

The wrist model Suunto M-9 is comfortable and multifunctional.

Tourists choose it for its small size and light weight, as well as the accuracy of determining the direction. The wrist device can also be used underwater.

A good American-made instrument is considered the most reliable, suitable for use in the field.

The case from aluminum, possesses the special durability, waterproof. The device is characterized by increased accuracy in determining the direction.

How to navigate with a compass

So what needs to be done:

1. First you need to determine the landmark to which you want to return, for example, it can be a tree.
2. Orientation begins with pressing a special latch and releasing the magnetic needle.
3. Taking the device and placing it horizontally on the palm, you must wait for the position of the blue arrow at 0 degrees of the scale, then turn the cover to install it with the slot towards you, and with the front sight to the object.
4. Having chosen the direction of movement, you should fix it and remember the value of the angle, called the "azimuth".
5. Constantly checking the direction, you need to start moving.
6. After you have reached the end point of movement, you should turn around your axis. This means that a rotation around its axis by 180 degrees was made. It turns out that they made a return to the starting point of the route.

Tourists and travelers, as well as hunters, can at any moment find themselves in unfamiliar places and lose the direction of their further movement. In such cases, with a compass, you can quickly determine the location.

But before choosing a compass, you need to study their types, properties, as well as for whom and for what purposes they are intended.

Video

How to use a compass in the forest, you will learn from our video.

Everyone who tried to put an electronic compass on their robot asked himself the following question: how, in fact, to get some kind of virtual arrow from this device that would point north? If we connect the most popular HMC5883L sensor to the Arduino, we get a stream of numbers that behave in a strange way when it is rotated. What to do with this data? Let's try to figure it out, because full-fledged navigation of the robot without a compass is impossible.
First, the device often referred to as a compass is actually a magnetometer. A magnetometer is a device that measures the strength of a magnetic field. All modern electronic magnetometers are manufactured using MEMS technology and allow measurements to be taken simultaneously along three perpendicular axes. So, the stream of numbers that the device gives out is actually the projection of the magnetic field on three axes in the coordinate system of the magnetometer. Other devices used for positioning and navigation have the same data format: accelerometer and gyro tachometer (aka gyroscope). The figure shows a simple case where the compass is horizontal to the earth's surface at the equator. The red arrow marks the direction to the north pole. The dotted line marks the projections of this arrow onto the corresponding axes. It would seem that this is it! The leg is equal to the leg by the tangent of the opposite angle. In order to get the direction angle, you will have to take the arctangent of the ratio of the legs: H = atan(X/Y) If we carry out these simple calculations, we will actually get some result. The only pity is that we still will not get the right answer, because we did not take into account a bunch of factors:

1. Displacement and distortion of the Earth's magnetic field vector due to external influences.
2. Effect of pitch and roll on compass readings.
3. The difference between geographic and magnetic poles is magnetic declination.

In this article, we will study these problems and find out how to solve them. But first, let's look at the readings of the magnetometer with our own eyes. To do this, we need to somehow visualize them.

1. Visualization of magnetometer readings

As you know, one picture is better than a thousand words. Therefore, for greater clarity, we will use a 3D editor to visualize the magnetometer readings. For these purposes, you can use SketchUp with the "cloud" plugin (http://rhin.crai.archi.fr/rld/plugin_details.php?id=678) This plugin allows you to load arrays of points from a view file into SketchUp: 212 -321 -515 211 -320 -515 209 -318 -514 213 -319 -516 The delimiter can be a tab, space, semicolon, etc. All this is specified in the plugin settings. In the same place, you can ask to glue all the points with triangles, which in our case is not required. The easiest way to save magnetometer readings is to transfer them via a COM port to a personal computer to a serial port monitor, and then save them to a text file. The second way is to connect an SD card to the Arduino and write the magnetometer data to a file on the SD card. Having dealt with recording data and importing them into SketchUp, let's now try to conduct an experiment. We will rotate the magnetometer around the Z axis, and the control program at this time will record the sensor readings every 100 ms. A total of 500 points will be recorded. The result of this experiment is shown below:
What can you tell by looking at this picture? First, you can see that the Z-axis has indeed been fixed - all points are located, more or less, in the XY plane. Secondly, the XY plane is slightly tilted, which can be caused either by the tilt of my desk or by the tilt of the Earth's magnetic field :) Now let's look at the same picture from above:
The first thing that catches your eye is that the center of coordinates is not at all in the center of the outlined circle! Most likely, the measured magnetic field is somehow "shifted" to the side. Moreover, this "something" has a tension higher than that of the natural field of the Earth. The second observation is that the circle is slightly elongated in height, which indicates more serious problems, which we will discuss below. And what happens if you rotate the compass around all axes at the same time? That's right, you get not a circle, but a sphere (more precisely, a spheroid). This is the area I got:
In addition to the main 500 points of the sphere, three more arrays are added, 500 points each. Each of the added groups of points is responsible for the rotation of the magnetometer around a fixed axis. So, the lower circle is obtained by rotating the device around the Z axis. The circle on the right is obtained by rotating around the Y axis. Finally, the dense ring of dots on the left is responsible for the rotation of the magnetometer around the X axis. Why these circles do not encircle the ball along the equator, we read below.

2. Magnetic inclination

In fact, the last drawing may seem a little strange. Why, being in a horizontal state, the sensor shows almost the maximum value on the Z axis?? The situation repeats itself if we tilt the device, for example, with the X axis down - again we get the maximum value (left circle). It turns out that the sensor is constantly affected by a field directed through the sensor down to the surface of the earth! There is really nothing unusual about this. This feature of the earth's magnetic field is called magnetic inclination. At the equator, the field is directed parallel to the earth. In the southern hemisphere - up from the earth at some angle. And in the northern hemisphere, as we have already observed - down. We look at the picture.
Magnetic inclination will not prevent us from using the compass in any way, so we will not think about it too much, but just take note of this interesting fact. Now let's move on to the problems.

2.1. Magnetic field distortion: Hard & Soft Iron

In foreign literature, magnetic field distortions are usually divided into two groups: Hard Iron and Soft Iron. Below is a picture illustrating the essence of these distortions.
hard iron I give you a certificate. The intensity of the earth's magnetic field is highly dependent on the earth's coordinates in which it is measured. For example, in Cape Town (South Africa) the field is about 0.256 Gauss (Gauss), and in New York it is twice that - 0.52 Gauss. On the planet as a whole, the intensity of the magnetic field varies in the range from 0.25 gauss to 0.65 gauss. For comparison, the field of a regular refrigerator magnet is 50 gauss, which is a hundred times more than the magnetic field in New York!! It is clear that a sensitive magnetometer can easily get confused if one of these magnets appears next to it. On a quadrocopter, of course, there are no such magnets, but there are much more powerful rare-earth magnets for brushless motors, as well as controller electronic circuits, power wires and a battery. Such sources of parasitic magnetic field are called Hard Iron. By acting on the magnetometer, they give some bias to the measured values. Let's see if Hard Iron has distortions in our sphere. The projection of the points of the sphere onto the XY plane looks like this:
It can be seen that the point cloud has some noticeable shift along the Y axis to the left. There is practically no displacement along the Z axis. Eliminating such a distortion is very simple: it is enough to increase or decrease the values ​​received from the device by the amount of the offset. For example, a Hard Iron calibration for the Y axis would be: Ycal_hard = Y - Ybias where Ycal_hard— calibrated value; Y- initial value; Ybias is the amount of displacement. To calculate Ybias, we need to fix the maximum and minimum value of Y, and then use a simple expression: Ybias = (Ymin-Ymax)/2 - Ymin where Ybias- the desired value of the displacement; Ymin- the minimum value of the Y axis; Ymax- the maximum value of the Y axis. soft iron Unlike Hard Iron, Soft distortion is much more insidious. Again, let's trace this kind of impact on the data collected earlier. To do this, let's pay attention to the fact that the ball in the picture above is not a ball at all. Its projection on the YZ axis is slightly flattened at the top, and slightly rotated counterclockwise. These distortions are caused by the presence of ferromagnetic materials near the sensor. Such material is the metal frame of the quadcopter, the motor housing, wiring, or even metal mounting bolts. To correct the situation with flattening, multiplying the sensor readings by a certain multiplier will help: Ycal_soft = Y * Yscale where Ycal_hard— calibrated value; Y- initial value; Yscale— scaling factor. In order to find all the coefficients (for X, Y and Z) it is necessary to identify the axis with the largest difference between the maximum and minimum value, and then use the formula: Yscale = (Amax-Amin)/(Ymax-Ymin) where Yscale is the desired distortion factor along the Y axis; Amax is the maximum value on some axis; Amin is the minimum value on some axis; Ymax- the maximum value on the Y axis; Ymin- the minimum value on the Y axis. Another problem, due to which the sphere turned out to be rotated, is eliminated a little more difficult. However, the contribution of such a distortion to the total measurement error is quite small, and we will not describe in detail the method of its “manual” leveling.

2.2. Automatic calibration

It must be said that manually obtaining accurate minimum and maximum readings of the magnetometer is not an easy task. For this procedure, at least, you will need a special stand in which you can fix one of the axes of the device. It is much easier to use the automatic calibration algorithm. The essence of this method is to approximate the cloud of obtained points by an ellipsoid. In other words, we select the parameters of the ellipsoid in such a way that it matches as closely as possible with our point cloud, built on the basis of the magnetometer readings. From the parameters selected in this way, we can extract the offset value, scale factors and coefficients for the orthogonalization of the axes. There are several programs on the Internet that can do this. For example, MagCal, or another one - Magneto. Unlike MagCal, in Magneto the calculated parameters are displayed in a ready-to-use form, without the need for additional conversions. This is the program we use. The main and only form of the program looks like this:
In the "Raw magnetic measurements" field, select the file with the source data. In the "Norm of Magnetic or Gravitational field" field, enter the value of the Earth's magnetic field at the point of our dislocation. Considering that this parameter does not affect the angle of deflection of the needle of our virtual compass in any way, I set the value to 1090, which corresponds to the value of 1 Gauss. Then we press the Calibrate button and we get:

1. offset values ​​for all three axes: Combined bias (b);
2. and the scale and orthogonalization matrix: Correction for combined scale factors, misalignments and soft iron (A-1).

With the help of a magic matrix, we will eliminate the flattening of our cloud and eliminate its slight rotation. The general calibration formula is as follows: Vcal \u003d A-1 * (V - Vbias) where Vcal is the vector of the calibrated value of the magnetometer for three axes; A-1 is the scale and orthogonalization matrix; Vbias is the displacement vector along the three axes.

3. Influence of the magnetometer tilt on the calculated direction

Next up is problem number two. At the beginning of the article, we already tried to calculate the angle between north and the compass needle. A simple formula works for this: H = atan(Y/X) where H- the angle of deviation of the compass needle from the north direction; X,Y are the calibrated values ​​of the magnetometer. Imagine now that we fix the X axis strictly in the direction of the north, and begin to rotate the sensor around this axis (we roll). It turns out that the projection of the field on the X axis remains unchanged, but the projection on Y changes. According to the formula, the compass needle will point either to the northwest or northeast, depending on which direction we roll. This is, stated at the beginning of the article, the second problem of the electronic compass. Geometry will help solve the problem. We only need to rotate the magnetic vector to the coordinate system given by the inclinometer. To do this, we alternately multiply two matrices of cosines by a vector: Vcal2 = Ry*Rx*Vcal where Vcal- magnetic vector, cleaned from Hard and Soft distortions; Rx and Ry- rotation matrices around the X and Y axes; Vcal2- magnetic vector, cleared of the influence of roll and pitch. The formula suitable for the controller program will look like this: Xcal2 = Xcal*cos(pitch) + Ycal*sin(roll)*sin(pitch) + Zcal*cos(roll)*sin(pitch) Ycal2 = Ycal*cos(roll) - Zcal*sin(roll) H = atan2(-Ycal2, Xcal2) where roll and pitch- inclinations around the X and Y axes; Xcal,Ycal,Zcal is the magnetometer vector (Vcal); Ycal2, Ycal2- calibrated values ​​of the magnetometer (we do not consider Zcal2 - it will not be useful to us); H is the angle between north and the compass needle. (You can find out who atan2 is here: http://en.wikipedia.org/wiki/Atan2)

3. Difference between geographic and magnetic pole

After we got a more or less accurate angle of the compass needle from the north direction, it's time to fix another problem. The fact is that the magnetic and geographic poles on our planet are very different, depending on where we make the measurement. In other words, the “north” that your hiking compass points to is not at all the north where the ice and polar bears are. To level these differences, a certain angle, called magnetic declination, must be added (or subtracted) to the sensor readings. For example, in Yekaterinburg, the magnetic declination is +14 degrees, which means that the measured readings of the magnetometer should be reduced by the same 14 degrees. In order to find out the magnetic declination in your coordinates, you can use a special resource: http://magnetic-declination.com/

Conclusion

In conclusion, a few tips for navigating with a magnetometer.

1. Calibration should be carried out exactly under the conditions in which the drone will make a real flight.
2. It is better to take out the magnetometer from the body of the robot on the rod. So it will be affected by less noise.
3. To calculate the direction, it is better to use a bunch of compass + gyroscope. At the same time, their readings are mixed according to a certain rule (data fusion).
4. If we are talking about an aircraft with a high heading speed, it is recommended to use a combination of compass + gyroscope + GPS.