Technical note: assessing GPS sensor accuracy using real-time kinematic device for livestock tracking

The technical aspects of global positioning system (GPS) sensors have been improved substantially over the years, making them valuable and popular tools for livestock tracking. Using GPS sensors allows producers and researchers to locate grazing livestock, monitor their behavior and distribution, and gather referencing information about the health status of the animals and pastures. However, interpreting the behavior of grazing livestock, such as cattle, from GPS data can be difficult due to positioning inaccuracies. Without knowing the positioning accuracy range of GPS sensors, achieving high-level confidence in determining grazing densities and identifying abnormal livestock movement patterns is challenging. In this study, the positioning accuracy of 3 different types of commercial GPS sensors was assessed using a survey-grade real-time kinematics (RTK) device. We outlined the procedures and essential equations and compared the recorded locations from the GPS sensors with reference locations collected from the RTK device. The results demonstrated statistically significant differences (P < 0.05) in positioning accuracy between different types of GPS sensors. The circular error probable (CEP) at 95% probability levels (CEP95) of the 3 sensors ranged from 2.46 to 11.06 m. This accuracy varied among individual sensors within the same brand and across different brands, which underscores the importance of evaluating the positioning accuracy of GPS sensors in livestock tracking. This study provides significant insights for animal scientists, ecologists, and livestock producers engaged in GPS sensor-related research and practices. Lay Summary GPS sensors play a pivotal role in modern livestock tracking, enabling producers and researchers to monitor grazing livestock, understand their behavior, and assess health indicators. Despite their widespread use, effectively interpreting the gathered data poses challenges due to positioning inaccuracies. This technical note delves into the methodology of assessing the positioning accuracy of 3 commercial GPS sensor types using a survey-grade real-time kinematics device. Results reveal meter-level precision with variations in accuracy among individual sensors and brands. The study emphasizes the critical need to evaluate GPS sensor positioning accuracy in livestock tracking, offering valuable insights for animal scientists, ecologists, and livestock producers for enhanced research and practices using GPS sensors.