The applications of the magnetic field sensors are complex. I summarized the types of sensors that can detect one of the properties of the magnetic field. After the theoretical overview it becomes clear when we measure the magnetic field how can we make it, how this technology can be used. One of the most versatile using is the circuit made of magneto resistor. This type of sensor is made out of a compass, which I also use for implement to an add-on card in a sensor fuse that main task to determine the position. Under the development I met some control and estimation algorithms that noise is used to refine existing data. Such a method of estimating the Kalman filter, which I used to estimate a more accurate position with the help of four sensors. The estimation process that I implemented in Matlab is also suitable for application, for example to short time lost GPS signal to replace.