My last thought is making a vehicle detector in front of the garage based on a magnetic field sensor. I read some materials and made a prototype based on MAG3110. I wonder if I can get better results in terms of detection distance. On the prototype I get a distance of about 60 cm from the front of the vehicle and about 120 cm when the sensor is mounted along the road and looks at the car from the side. The documentation shows that MAG3110 has a measuring range of +/- 10 gauss. I've seen sensors like these that have 16 gauss. I wonder if this parameter is responsible for the "size" of the field in which the sensor sees changes. In other words, will this 16 gauss increase the detection range?
The max field strength figures don't tell you the sensitivity or noise floor. Have a look in the data sheet for that information.
So I have to compare parameter sensitivity and noise floor not full scale range?
MAG3110: Sens μT: 0,1 Noise μT: 0,1 BNO055: Sens μT: 0,3 Noise μT: ? LSM9DS1: Sens μT: 0,014 to 0,058 Noise μT: ? It looks like the sensor LSM9DS1 will be the best for my tasks? Do I think right?
The earth's magnetic field is somewhere in the region of 20-60 μT so that is the range you're interested in. Having a sensor that can measure 1000 μT isn't going to help you detect the small changes due to the presence of a car body.
When comparing sensors you need to know what is smallest change that can be detected. That's the sensitivity spec. You also have to consider noise. If the noise if high then you need to use a low pass filter which makes the sensor slow to respond to changes.
Magnetic effects fall off as the inverse-cube of distance, so don’t expect dramatic increase in range - however you should also be able to detect larger pieces of iron/steel at larger distances than small pieces.