I’ve been asked in private messages. Why do I dislike magnetic compasses and what are their disadvantages?
In short, I can answer this way - I certainly like magnetic compasses, especially when the device is very small and should fit in a pocket. For example, a GPS navigator or a smartphone or other devices that do not require very high accuracy in determining the course. Sometimes, technically, nothing can be used except a magnetic compass.
Now about the various problematic issues:
- Magnetic compasses must be calibrated every time the installation location is changed.Or they removed it and reinstalled it.
- The magnetic lines of the planet earth at different latitudes have different angles relative to the earth’s surface. The further away you are from the equator, the more the accuracy of the magnetometer readings depends on the Z axis.
- Even a slight tilt of the magnetometer relative to the earth’s plane causes strong changes in readings (and this property increases with distance from the equator in latitude). Therefore, magnetometers are supplemented with accelerometers and gyroscopes to compensate for these inclinations.
- Accelerometers and gyroscopes may incorrectly compensate for the tilt of the magnetometer during severe rocking or shaking. For example, a ship on shallow and frequent waves or a car on a road with coarse gravel. In this case, special algorithms are used to integrate and filter data from the magnetometer and accelerometer and gyroscope.
- Even if you have taken into account everything that is written above, you need to accurately take into account the magnetic declination of your region.
- Even if you have taken into account everything that is written above, magnetic anomalies may occur while driving, both of a geological nature and from massive metal structures that you are passing by in a car.
- Under ideal conditions, it is possible to achieve high accuracy in indicating the course, but in real life so many factors affect the accuracy of the magnetic compass course that unpredictable errors in indicating the course of 5 or 10, and sometimes 30 degrees can be expected.This is acceptable when you’re walking through the woods. The electronic compass shows you the arrow with an accuracy of sometimes 10 degrees, sometimes 5 degrees. You’ll come where you need to anyway.But if you are doing radio direction finding, an error in measuring the course, taking into account the distance to the radiation source, can give a significant error. So why use a heading guidance system with so many features and weaknesses in a radio direction finding system? Of course, a magnetic pointer is much better than not having one. But the DATHFK-type course pointer has high accuracy, is predictable, and does not have all the disadvantages described above. It only requires more space to install.
Short conclusion: a magnetic pointer is fine, but there is no high accuracy, there are many dependencies, calibration is required during reinstallation, requires little space for installation. DATHFK- requires more space for installation. High accuracy and predictability.
P.S. I wrote it quickly without any preliminary preparation. Maybe I forgot something…