Accuracy and precision of GNSS in the field

Global Navigation Satellite Systems (GNSSs) have revolutionized the way we locate ourselves on the Earth. We use the technology routinely in our cars and with our smart devices. Modern GNSS receivers are easy to use and relatively cheap and offer researchers from different backgrounds and levels of expertise the opportunity to measure location to unprecedented levels of speed and accuracy. However, those embarking on surveys utilizing this technology need to be aware of the underpinning principles and concepts that these clever devices hide in order to maximize their effectiveness and achieve results that are “fit for purpose.” This chapter therefore defines both accuracy and precision for mapping purposes and considers those factors that can affect the accuracy a survey can achieve, such as instrument selection, environmental factors, coordinate system selection, and, with the aid of some examples, how to set up a survey. We are not concerned with air or sea navigation where safety-of-life applications have led to the development of integrity as a means of describing navigation performance, thus providing a level of confidence in the location information supplied.