The rapid development of small unmanned aerial systems (UASs) in recent years has triggered considerable interest in their application for precision agriculture. The decreasing cost, the ultra-high spatial resolution and the increased flexibility of image acquisition have made UAS remote sensing an ideal technique for identifying, at close-to-real-time, field patterns. This chapter provides an overview of UAS platforms and sensors, and flight planning and imagery acquisition, before moving on to consider stitching and ortho-rectification in UAS image processing. The chapter reviews the applications of UAS imagery and methods of image analysis and incorporates a detailed case study. Finally, the chapter looks ahead to future research trends in this area.