A UAV equipped with a digital camera
estimated and measured data . Therefore , it can be used to assess the performance of land levelling in paddy fields .
WATER MANAGEMENT
Currently , the largest amount of water consumed in the world is in the irrigation of crops [ 8 ]. Rice seeding under flooding requires a large amount of water ( 15,000 – 20,000 m 3 / ha ) [ 9 ]. The availability of water for irrigation is becoming scarce due to climate change and competition with the other sectors . Therefore , it is essential to use irrigation water more efficiently and effectively [ 10 ].
Previous studies demonstrated that precision irrigation techniques can improve the efficiency of water use by proper monitoring of the water body distribution in the field . UAV-based remote sensing data can be used for a fast and reliable identification of the water body extent at a local scale with an average kappa coefficient of the water body identification above 0.9 [ 11 ]. This information can be processed into multi-temporal
high-resolution water movement pattern maps highlighting the status of the flooded areas by image processing techniques . These maps provide essential information to help irrigation managers enhance decision-making in the management and operation of the irrigation system .
PLANT POPULATION DENSITY MONITORING
Rice tiller numbers are a key indicator in plant population density monitoring . They provide information on the status of the crop as well as potential yield . This information can be used to calculate the amount of fertiliser and pesticide to be applied in the field [ 12 ].
Ground-based sampling methods have been used to count the tiller numbers for determining plant populations in rice fields [ 13,14 ]. The sampling method is performed by randomly choosing several different locations within a plot to perform tiller counting in a 25 cm x 25 cm square frame . However , this method is usually
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