Radiometric calibration of low altitude multispectral remote sensing images

Abstract: The small size and low cost micro-UAV information acquisition technology platforms have been widely applied in agricultural field in recent years. It has become the inevitable trend of development of precision agriculture and has offered a fast and flexible way to acquire data for crop management and monitoring, capable of timely provision of high resolution images. The key technology for remote Sensing information acquisition based on micro UAV in the world, which includes the development of micro UAV remote sensing platforms, information acquisition technology, image processing, and analysis and application of crop management, is reviewed in this paper. Micro UAV mainly has two types: rotor helicopter and fixed-wing aircraft. The rotor helicopter has been used more widely in acquiring information of the field, because it has the ability of taking off and landing vertically, fixed-point hovering, and slow cruising. Japan was the first country that has used the micro-UAV in agricultural production, and is one of the countries that have the best and most mature technologies in using remote UAV in agriculture today. The United States, Netherlands, Israel, and the United Kingdom also have a very good development all over the world. The beginning of research and development of micro UAV in China was much later than the other developed countries, but it has a booming development and grows rapidly. In this paper, parameters and characteristics of different models of the micro UAVs from eight companies in China have been listed for comparison. In remote sensing information acquiring systems, due to the limited load capacity of micro-UAV, digital camera and light-weight multispectral camera are two main instruments that are used on micro UAV for remote sensing information acquiring. How to adjust the posture of airborne remote sensors quickly and accurately so that the detecting target is always in the center of monitoring view, and how to realize remote controlling, image and information capturing, and transmission wirelessly are some of the focuses of UAV remote sensing technology at present. Limited by the stability and load capacity of the micro UAV, the remote sensing image always appears with the defects including a small view, large angle inclination, and serious irregular image overlap. So, solving the problem of correction, matching, mosaicing, fusing, and analyzing of the remote sensing images is one of the most important research work in this field. Nowadays, the main application of micro UAV focuses on the detection of growing nitrogen levels and the generation of fertilization strategy for rice, cotton, and other staple crops. However, the usage of micro UAV is limited due to the following defects: 1) its small size, making it easily influenced by wind, and short battery life; 2) poor accuracy of navigation system and balance control system; 3) serious leakage or reduplication of capturing images caused by the imprecise heading overlapping and routes bending; 4) difficulty of image correcting, matching, mosaicing, fusing, and analyzing for the remote sensing images; 5) the error of UAV equipment and usage is difficult to control. According the review, the further research on key technology focusing on high stability, big load capacity, long life time, and high resolution data for crop management have been proposed. The micro UAV information acquisition platform is a good complement of satellite and aerial remote sensing technologies for monitoring agricultural information and generating prescription maps for precision agriculture.