Nowadays, fully automated solutions are being considered for precision agriculture. One such solution is the use of Unmanned Aerial Vehicle (UAV). UAVs use a combination of multiple technologies and programming such as Smart Sensors, Digital Electronics, Internet of Things, Satellite Technology, etc. which makes them an efficient technique to a fully automated farming solution. Precision agriculture or smart agriculture include field mapping with multiple onboard sensors to map terrain and detect soil health or vegetation. This paper reviews on the UAVs in precision agriculture and their ability to evaluate the best paths for field mapping.