Twenty First Century Aerospace Technology Co.

Twenty, China

Twenty First Century Aerospace Technology Co.

Twenty, China
Time filter
Source Type

Nannan Z.,Twenty First Century Aerospace Technology Co. | Sun W.,Twenty First Century Aerospace Technology Co.
Proceedings of the International Astronautical Congress, IAC | Year: 2016

China is in the rapid development of urbanization. Urbanization brings great convenience to people in many ways. On the other hand, it also brings a series of problems, such as population explosion, environment pollution, farmland occupation, ecological system degradation. All these problems bring great challenges for city management, especially for the mega-city as Beijing, which requires timely spatial data in combination with other data for intelligent management. Traditional methods of information acquisition become the constraints of city managementdue to long period and high cost. Therefore, it is very urgent to use new and intelligent information acquisition technology to carry out real-time monitoring and effective city management. Based on regular satellite imagery acquisition abilities and more than 10 years expertise in image analysis, processing and interpretation, more than 70 features are extracted from Satellite imagery to provide 100 Services for government departments in Beijing. These applications can be grouped into 6 categories: Agriculture, City Operation, Environment Protection, Forestry and City Green Monitoring, Water, Land Resources/Uses. Based on guaranteed high resolution satellite imagery, 21AT provides updated, objective and independent land cover survey, and subsequent change surveillance of interested features and targeted areas. To integrate the changes with other geospatial data provides comprehensive analysis, statics and various government reports, consequently keeping city in order and running smoothly and efficiently. Intelligent City Monitor based on Beijing series small earth observation satellites is an innovative approach for land cover survey and monitoring; and is the enabler for intelligent city management.

Zhao S.,Southwest Jiaotong University | Sun P.,Twenty First Century Aerospace Technology Co.
International Journal of Online Engineering | Year: 2013

In view of the limited rational decision made by decision-makers in reality, multi-objective Lattice Order Decision Making is introduced in the new airport site selection and Lattice Order Decision evaluation index system is constructed. Based on the types of index, processed the index into dimensionless, Integrate decision-makers' subjective judgment and the data dispersion feature to calculate the relative weights of the evaluation index. Combined with Decision-making moment, calculate the value of comprehensive differences of the schemes, and realize the Lattice Ordering of the schemes. Apply this decision-making method to evaluate three sets of alternative airport site selection schemes in Chengdu. The outcome is consistent with the actual situation, which proved that the decision-making method is reasonable.

Chen T.,Twenty First Century Aerospace Technology Co. | Liang S.,Water Resources University | Wen Q.,Twenty First Century Aerospace Technology Co.
Proceedings of the International Astronautical Congress, IAC | Year: 2013

This study investigated the characteristics of spatial and temporal variability of vegetation and evaluated the relative roles of various affecting factors in source region of the Yangtze River by means of Empirical Orthogonal Function (EOF) and wavelet decomposition analysis. The main remote sensing data was Global Inventory Modeling and Mapping Studies (GIMMS) Normalized Difference Vegetation Index (NDVI) that from 1982 to 2001, and the May-September data were used for the EOF analysis that focused on the spring bloom. Three principal modes, which explain about 77% of the total variance, have been identified. The first EOF mode explains 70.51% of the variability and shows that major vegetation coverage change is spatially consentaneous, but the amplitude of southwest region is higher than northeast. At the time series, there is obvious seasonal and interannual cycle time and May reaches the peak value of time coefficient. The second EOF mode (3.72%) indicates that the spatial pattern corresponds with the hydrogeological unit distribution. By wavelet decomposition, the second series have 3-4 years and 22 years cycle, which is correlated with the period time of base flow as the sign of groundwater capacity in source region of the Yangtze River. The third mode (2.33%) which the spatial structure presents north west west- south east east (NWW-SEE) banded and the time coefficient shows more than 40 years long cycle and 3-4 years short cycle is seen to be significantly correlated with precipitation spatial distribution. In conclusion, at the seasonal scales the major variability of coverage in source region of the Yangtze River is controlled by May vegetation germination and growth change, and the long-period evolution of vegetation depends on hydrogeological conditions. Copyright© (2013) by the International Astronautical Federation.

Yan M.,CAS Institute of Remote Sensing | Wang C.,CAS Institute of Remote Sensing | Ma J.,CAS Institute of Remote Sensing | Wang Z.,Twenty First Century Aerospace Technology Co. | Yu B.,Twenty First Century Aerospace Technology Co.
Photogrammetric Engineering and Remote Sensing | Year: 2016

When an optical remote sensing satellite is imaging the Earth in-orbit, the propagation direction of the Line of Sight (LOS) will be changed because of atmospheric refraction. This will result in a geolocation deviation on the collinear rigorous geometric model for direct georeferencing, pushbroom images. To estimate and correct the atmospheric refraction geolocation error, the LOS vector tracking algorithm is introduced and a weighted mean algorithm is used to simplify the ISO standard atmospheric model into a troposphere and stratosphere, i.e., two layers spherical atmosphere. The simulation result shows the atmospheric refraction will introduce about 2 m and 7.5 m geometric displacement when the spacecraft is off-pointed view at 30 and 45 degree angle, respectively. For a state-of-theart high resolution satellite, the atmospheric refraction displacement shall be corrected. The method has been practiced in the DMC3/TripleSat Constellation to remove the atmospheric refraction geolocation error without ground control points. © 2016 American Society for Photogrammetry and Remote Sensing.

Li X.,CAS Institute of Remote Sensing | Wang H.,CAS Institute of Remote Sensing | Zhou S.,Twenty First Century Aerospace Technology Co. | Sun B.,Chinese Academy of Forestry | Gao Z.,Twenty First Century Aerospace Technology Co.
Chinese Geographical Science | Year: 2016

Aiming for the restoration of degraded ecosystems, many ecological engineering projects have been implemented around the world. This study investigates the ecological engineering project effectiveness on vegetation restoration in the Beijing-Tianjin Sand Source Region (BTSSR) from 2000 to 2010 based on the rain use efficiency (RUE) trend in relation to the land cover. More than half of the BTSSR experienced a vegetation productivity increase from 2000 to 2010, with the increasing intensity being sensitive to the indicators chosen. A clear tendency towards smaller increasing areas was shown when using the net primary productivity (NPP, 51.30%) instead of the accumulated normalized difference vegetation index (59.30%). The short-term variation in the precipitation and intra-seasonal precipitation distribution had a great impact on the remote sensing-based vegetation productivity. However, the residual trends method (RESTREND) effectively eliminated this correlation, while incorporating the variance and skewness of the precipitation distribution increased the models′ ability to explain the vegetation productivity variation. The RUE combined with land cover dynamics was valid for the effectiveness assessment of the ecological engineering projects on vegetation restoration. Particularly, the result based on growing season accumulated normalized difference vegetation index (ΣNDVI) residuals was the most effective, showing that 47.39% of the BTSSR experienced vegetation restoration from 2000 to 2010. The effectiveness of the ecological engineering projects differed for each subarea and was proportional to the strength of ecological engineering. The water erosion region dominated by woodland showed the best restoration, followed by the wind-water erosion crisscross regions, while the wind erosion regions dominated by grassland showed the worst effect. Seriously degraded regions still cover more area in the BTSSR than restored regions. Therefore, more future effort should be put in restoring degraded land. © 2016, Science Press, Northeast Institute of Geography and Agricultural Ecology, CAS and Springer-Verlag Berlin Heidelberg.

Liu F.,CAS Institute of Remote Sensing Applications | Wang Z.,Twenty First Century Aerospace Technology Co.
ICETC 2010 - 2010 2nd International Conference on Education Technology and Computer | Year: 2010

Directed Acyclic Graph (DAG) has been widely used in Grid workflow modeling, since it deals with the mass data with a specific user-defined Grid Wordflow job scheduling. However, DAG has limit modeling power, for a DAG model cannot express process state information. DAG-extended model provides solutions to "glue" multiple algorithm attributes, scalable algorithm run-time environments, various matchmaking agents, parallel data features and operational attributes together. Currently, it is still a pending issue for the existing Grid workflow based on the DAG-extended scheduling to express complex relationships among various tight-coupling remote sensing algorithms with a series of definition toolkit,such as deletion algorithm, for it can only describe the logical feature of remote sensing processing algorithms but can not show the parallel feature of algorithms. Aiming at this problem, this paper proposes a DAG -extended deletion algorithm in Graphical Abstract Grid Workflow Model for remote sensing quantitative retrieval application. In this paper, we mainly: (1) discuss the limits of current Grid workflow models applied in the remote sensing field, and (2) modify the traditional DAG Grid Workflow model to the DAG-extended Grid Workflow model, especially describing the logical feature of remote sensing algorithms. Besides, (3) based on the new defined tool - DAG-Extended deletion algorithm in graphical Grid workflow model, we give the concrete implementation example to present the dynamic modification achievement of this composition tool and illustrate its benifits over algorithms based on the traditional DAG Graphic-oriented Abstract Grid Workflow model. © 2010 IEEE.

Ji W.,Twenty First Century Aerospace Technology Co. | Wang Z.,Beijing Landview Mapping Information Technology Co. | Wen Q.,Twenty First Century Aerospace Technology Co.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

Urban grass is the interference object of vegetable species recognition. Therefore choose an instance of urban grass to retrieve the spectrum curve of interference vegetation. The spectrum retrieval of vegetation species includes three steps, 1) the Hyperspectral image preprocessing, 2) the high fidelity image fusion, and 3) the purity endmember extraction. Firstly, the Hyperspectral image is preprocessed including the removal of bad bands, the radiance calibration, and the FLAASH atmospheric correction. Secondly, the Gram-Schmidt fusion method which has an advantage of spectral high fidelity was employed to fuse the Hyperspectral image and the high spatial panchromatic image. Thirdly, the grass reference vectors was applied in masking the fusion image and then the minimum noise fraction was used to forward and inverse transform the masking image. The pixel purity index of image was calculated after de-noising and then the threshold range was determined to obtain the region of interest that has high purity. The principal component analysis was adopted to forward transform the visible, near infrared, shortwave infrared channels respectively and then the first and second bands of each channel were selected. The optimum index factor was used to acquire the eigenvalues of optimum bands combination and then the N-dimensional visualization was applied in extracting study area endmember of grass species. Finally the spectrum curve of urban grass was retrieved from the average endmember spectral of original fusion image. © 2014 SPIE.

Liu F.,CAS Institute of Remote Sensing Applications | Wang Z.,Twenty First Century Aerospace Technology Co.
2010 18th International Conference on Geoinformatics, Geoinformatics 2010 | Year: 2010

Emergency Response Mechanism (ERM) for remote sensed image sequential deficiency is extremely crucial and the concerned researches are in urgent need. STARFM (Spatial and Temporal Adaptive Reflectance Fusion Model, STARFM) is such a fusion method for image sequences prediction, which is a sound theoretical and valid applicable approach. Gao et al. have successfully produced synthetic Landsat imagery with the corresponding approach, and Hiker et al. have applied it in coniferous study. However, STARFM algorithm has limit modeling power, for it has not fully considered disturbance events occurring within the observation process, meanwhile this paper does not supply an accuracy of synthetic images with variance indicators. Currently, it is still a pending issue addressing the stated estimation and uncertainty existence of sensor measurement values. In this paper, it is assumed that multiple sources data cross-use could minimize the observation error by effective blending technology. Under this assumption, we propose to modify the existing STARFM model, to optimize the predicted imagery through data assimilation theory, and the resulting synthesis image after iterations will be close to the true image. This paper proposes a practical approach of dynamic assimilated STARFM algorithm (DASTARFM), and supplies an application of crop yield estimation by remote sensing technology. In this paper, we mainly: (1)discuss the limits of the current concerned image synthetic researches; and (2) give a description of the practical approach which is featured as adaptive to the dynamic optimization, namely the dynamic optimized STARFM. Besides, (3) based on the new model-DASTARFM, we give the concrete implementation example to present the optimal estimated achievement of this model and illustrate its benefits over the typical algorithm according to the prior and post variances.

Ji W.,Twenty First Century Aerospace Technology Co. | Wang Z.,Twenty First Century Aerospace Technology Co.
34th Asian Conference on Remote Sensing 2013, ACRS 2013 | Year: 2013

The cloud platform firstly parses the requirements of the virtual constellation to determine service mode and then decomposes corresponding service process to determine interface location. Further, based on loosely coupled principle between interface and function, an input interface, operations and an output interface are split. As an instance of observation plan service, an UML sequence diagram is used to describe the application scenes, the request and response parameters, the communication performance, the parameters source of each service-side interface and the timing constraint between interfaces. On this basis, this paper defines the XML schema for every interface parameters. An UML static structure is used to analyze interface type to form interface methods tree. In conclusion, this study promotes the change of service mode from single satellite programming to multi-satellites collaborative observation and to some extent improves products quality of service.

Sun W.,Twenty First Century Aerospace Technology Co.
Proceedings of the International Astronautical Congress, IAC | Year: 2015

Beijing series Earth Observation satellites are operated by a Beijing based high-tech enterprise, Twenty First Century Aerospace Technology Co. Ltd (21AT). The company is the first and only commercial EO satellite operator in China. Its first generation satellite, Beijing-1 small satellite developed in cooperation with SSTL, was launched in 2005 and had successfully provided data and service for wide range of EO applications in China, which includes land resources management, disaster response, forestry and agriculture monitoring, water monitoring for safety and protection, urban planning and development. Especially, it provided operational comprehensive intelligent management service for Beijing municipal government based on key element and its consequent change detection, which derived from guaranteed quarterly Beijing-1 satellite images. Also, Beijing-1 has provided disaster responses through International Charter and data to international customers through the international Disaster Monitoring Constellation (DMC). 21AT through the success of Beijing-1 satellite demonstrates that guaranteed timely data is the enabler for operational services that made the commercialization of EO satellites possible. Following the success of Beijing-1, a new high resolution <1m TripleSat Constellation have been launched on 10 July 2015 to provide sustainable data source for Beijing Intelligent Management System and bring the unique optical satellite data source to the world. The constellation consists of three identical satellites, will be able to provide daily targeting capability anywhere on the Earth and provide dependable timely data and associated operational services for worldwide customers.

Loading Twenty First Century Aerospace Technology Co. collaborators
Loading Twenty First Century Aerospace Technology Co. collaborators