Foto del docente

Maurizio Canavari

Full Professor

Department of Agricultural and Food Sciences

Academic discipline: AGR/01 Agricultural Economics and Rural Appraisal

Useful contents

GNSS (Global Navigation Satellite System)

The "Global Navigation Satellite System" or GNSS is a system that, in agriculture, is extremely useful for customized land management, allowing the mapping of production and variable rate distribution. In addition, in navigation, it helps to maintain parallel passes avoiding overlapping or non-treatment zones. This technology allows to increase the quantity and quality of outputs, together with profitability. As a result, energy costs and waste produced are also reduced. The end result is greater safety for operators and the environment.

GNSS satellite systems are structures that use satellite constellations to learn positioning and allow navigation to any point on the earth's surface, using radio signals emitted by satellites. The most widely used system is NAVSTAR GPS, but there are also several others, such as GLONASS (Russian system) and the European GALILEO system, designed for civil purposes only.

Thanks to these constellations, in orbit along the earth's surface, and to control stations, the ground receiver (user) is able to know its more or less precise position depending on the number of visible satellites, their configuration, measurement modes, type and number of receivers. Depending on these characteristics, it is possible to obtain coarse determinations, with positioning errors that can be evaluated in meters, up to reach accuracies of agricultural interest of the order of a centimetre and (under certain conditions) even a millimetre.

The three categories of positioning are: the absolute positioning, obtained with a single receiver and with errors up to 15 meters, the code differential positioning (DGPS), obtained with two receivers called MASTER and ROVER and with errors around the meter and the phase differential positioning (RTK) that reaches accuracies below the centimeter.

The main navigation systems are:

  • Guide bar, which involves an on-board computer connected to a GNSS. The trajectory is managed by the operator who, however, thanks to LEDs is able to maintain the right trajectory to follow in the field;
  • Assisted driving, which can be characterised by a pinion adherent to the steering wheel rim or by an electric motor acting on the steering column. Through assisted driving, the operator only has to make headland turns manually. It works in the case of straight trajectories.
  • Semi-automatic steering, featuring a control and data management unit, a display, a steering sensor and an actuator for electro-hydraulic control of the steering system. In this case the steering control is total and no operator intervention is required even at the headland;

These systems increase actual working capacity and width, increase actual working hours and reduce operator fatigue.

As far as production mapping is concerned, on the other hand, sensors are used, together with a GPS antenna and a CPU for data processing:

  • Material flow sensors;
  • Feed rate sensors;
  • Effective working width sensors.

Mapping is fundamental for:

  • planning transport logistics and storage operations;
  • carry out an analysis of field yields and maximize them;
  • track production.