GPS-Aided Land-Based Navigation and Precision Farming Applications: Improving GPS Solutions by Means of MEMS-IMU and Low-Cost Sensors

The land-based navigation, paying attention to precision farming, is the research topic: the final purpose is the design and development of a guidance-aided system focusing on a lew-cost GPS receiver able to provide a pseudorange-based solution only. Specific tests have been carried out to perform the particular trajectories followed by the vehicle in agricultural applications, whose accuracy target is typically 1 m. Results show that the low-cost receiver is affected by a drift in time which is mainly detected while turning and causing a deviation from the optimal reference solution. Thus, the goal is to correct this behaviour because the deviation accumulates during time and causes a not optimal treatment of the field (waste of material and money). Paying attention to the cost of the system, a new idea was proposed: the integration between the low-cost GPS with a magnetometer/digital compass. A dedicated algorithm was also implemented, taking the heading provided by the magnetometer and using it to correct the deviation in rums. Unluckily a magnetometer is deeply influenced by ferrous materials and the sensor is supposed to be installed on the vehicle, which is mainly made by metal. As a consequence, the sensed measurements are affected by a deviation from the actual magnetic field. Those disturbances need to be properly reduced by an autocalibration procedure. First of all, this paper deeply analyzes the performances of those particular low-cost GPS receivers; furthermore a solution is presented by means of the integration with a magnetometer. Results will be shown with great attention to future developments and improvements of the low-cost system suggested for supporting the guidance in precision farming applications.