No abstract

The ZiYuan‐3 surveying satellite (ZY‐3), launched on 9th January 2012, is China's first civilian high‐resolution stereo mapping satellite. To ensure the mapping accuracy of ZY‐3, considerable research has been conducted since its launch on the calibration and validation of its three‐line array charge‐coupled device (CCD) sensors (TLC sensors). Its dynamic exterior systematic errors (such as camera installation errors) and static interior distortion were eliminated using 1:2000 digital orthophotomaps and digital elevation models (DEMs) of the Dengfeng (Henan) and Tianjin areas of China as control data. Various CCD alignment calibration models were compared, on the basis of their geometric accuracy after calibration, to determine the optimal model. Finally, validation experiments were performed using ZY‐3 TLC images and ground control points (GCPs) collected over Anping in Hebei Province, Zhaodong in Heilongjiang Province and the Taihang Mountain area in China. The positioning accuracy attained its theoretical value over the Anping and Zhaodong areas. Using GCPs whose image coordinates were obtained manually, the plan and height accuracy were found to be better than 3 m and 2 m, respectively.

Background Mental fatigue is usually caused by long-term cognitive activities, mainly manifested as drowsiness, difficulty in concentrating, decreased alertness, disordered thinking, slow reaction, lethargy, reduced work efficiency, error-prone and so on. Mental fatigue has become a widespread sub-health condition, and has a serious impact on the cognitive function of the brain. However, seldom studies investigate the differences of mental fatigue on electrophysiological activity both in resting state and task state at the same time. Here, twenty healthy male participants were recruited to do a consecutive mental arithmetic tasks for mental fatigue induction, and electroencephalogram (EEG) data were collected before and after each tasks. The power and relative power of five EEG rhythms both in resting state and task state were analyzed statistically. Results The results of brain topographies and statistical analysis indicated that mental arithmetic task can successfully induce mental fatigue in the enrolled subjects. The relative power index was more sensitive than the power index in response to mental fatigue, and the relative power for assessing mental fatigue was better in resting state than in task state. Furthermore, we found that it is of great physiological significance to divide alpha frequency band into alpha1 band and alpha2 band in fatigue related studies, and at the same time improve the statistical differences of sub-bands. Conclusions Our current results suggested that the brain activity in mental fatigue state has great differences in resting state and task state, and it is imperative to select the appropriate state in EEG data acquisition and divide alpha band into alpha1 and alpha2 bands in mental fatigue related researches.