The principle of operation of the digital compass
In connection with the widespread mobile platform android and gps chips as part of the final products in particular, I became interested in the idea of ​​the digital compass, around which so many questions now arise.
So, the object we are considering is a compass, which is based on the principle of construction on the definition of coordinates, using satellite navigation systems. However, in practice there are cases when the compass incorporates as a receiver a block of magnetoresistors (the principle of resistance change from the position of an object in absolute space) or Hall elements. Hall elements are built on the basis of micromechanical systems that are highly sensitive to a change in the magnetic field. In a particular case, the charge distribution on a silicon wafer is influenced by the Earth’s magnetic field. Instruments on magnetoresistors and Hall elements personify the compass in its classic form as an autonomous measuring instrument, unlike the systems of the “collective” type, the input information for which comes directly as a satellite signal. As a result, systems tied to an external source of information are essentially devices with an indication of a traveling angle in the form of a compass.
Since in practice we deal most often with determining the location and direction by means of navigation systems, an example of this is at least android with its google maps application, then the principle of operation of the algorithm for just such a use case is given:
1. Using satellite signals, we take readings of the coordinates of the satellite navigation system receiver (and, accordingly, the object)
2. We note the point in time at which the determination of coordinates was made.
3. We expect a certain time interval, which is short enough for better results.
4. Re-determine the location of the object.
5. The simplest navigation problem of calculating the velocity vector of motion from the obtained coordinates of two points and the size of the time interval is solved, after which, knowing the vector, we can easily obtain:
a) direction of travel
b) movement speed
6. Go to step 2.
')
As you can see, the operation of the algorithm is provided cyclically and the starting point for the start of the next vector will be the end of the guide vector for the last time interval.
The disadvantages of this method in applying digital compassing are:
if the object is stationary in absolute space, the direction of motion cannot be obtained, the points of fixation of coordinates coincide in this case.
As an exception, rather large objects (for example, large sea vessels), where it is possible to install 2 receivers (for example, on the bow and stern). Thus, the coordinates of two points can be obtained immediately, even if the object is stationary, and go to step 5.
It is also necessary to take into account the accuracy of determining the coordinates of satellite positioning systems and its impact on slow-moving objects, due to the spread of positioning errors.
So, the object we are considering is a compass, which is based on the principle of construction on the definition of coordinates, using satellite navigation systems. However, in practice there are cases when the compass incorporates as a receiver a block of magnetoresistors (the principle of resistance change from the position of an object in absolute space) or Hall elements. Hall elements are built on the basis of micromechanical systems that are highly sensitive to a change in the magnetic field. In a particular case, the charge distribution on a silicon wafer is influenced by the Earth’s magnetic field. Instruments on magnetoresistors and Hall elements personify the compass in its classic form as an autonomous measuring instrument, unlike the systems of the “collective” type, the input information for which comes directly as a satellite signal. As a result, systems tied to an external source of information are essentially devices with an indication of a traveling angle in the form of a compass.
Since in practice we deal most often with determining the location and direction by means of navigation systems, an example of this is at least android with its google maps application, then the principle of operation of the algorithm for just such a use case is given:
1. Using satellite signals, we take readings of the coordinates of the satellite navigation system receiver (and, accordingly, the object)
2. We note the point in time at which the determination of coordinates was made.
3. We expect a certain time interval, which is short enough for better results.
4. Re-determine the location of the object.
5. The simplest navigation problem of calculating the velocity vector of motion from the obtained coordinates of two points and the size of the time interval is solved, after which, knowing the vector, we can easily obtain:
a) direction of travel
b) movement speed
6. Go to step 2.
')
As you can see, the operation of the algorithm is provided cyclically and the starting point for the start of the next vector will be the end of the guide vector for the last time interval.
The disadvantages of this method in applying digital compassing are:
if the object is stationary in absolute space, the direction of motion cannot be obtained, the points of fixation of coordinates coincide in this case.
As an exception, rather large objects (for example, large sea vessels), where it is possible to install 2 receivers (for example, on the bow and stern). Thus, the coordinates of two points can be obtained immediately, even if the object is stationary, and go to step 5.
It is also necessary to take into account the accuracy of determining the coordinates of satellite positioning systems and its impact on slow-moving objects, due to the spread of positioning errors.
Source: https://habr.com/ru/post/128158/
All Articles