Drones can detect and map Japanese knotweed, so the problem areas can be located, quantified, managed and neutralised. Because the knotweed is mapped from above, the risk of spreading is eliminated unlike surveying knotweed from the ground. A 250-acre site that we recently surveyed with a UAV in Co Kerry had very serious issues with knotweed infestation, which only came to our attention after surveying the site. From our aerial ortho-rectified imagery, we could detect and create polygons in CAD (computer-aided design), which outlined each cluster of knotweed. As the client accepted our proposal to map the knotweed, these polygons were then converted for use in Google Earth so anyone could use the mapped outline of knotweed on their smartphones to view the location and extent of each individual bush of knotweed. Each polygon was numbered and was given an area in metres squared and were outputted. Had we carried out this survey on the ground using either GPS or total station, there would have been a large risk of making the problem worse by spreading it. The information showing the location and extent of each knotweed bush provides landowners with the ability to manage a campaign of knotweed eradication, by being able to view the polygons within Google Earth means that each knotweed eradication team can be assigned different areas. Our next job with this client is to re-survey the same site using our 'Egret' drone to quantify the reduction in knotweed infestation and to produce updated knotweed polygons to reflect what knotweed is currently on site. Paudie Barry is a land surveyor/UAV operator and managing director with Baseline Surveys Ltd.