Key Laboratory of Geoscience Spatial Information Technology
Key Laboratory of Geoscience Spatial Information Technology
Liu H.,Chengdu University of Technology |
Liu H.,Key Laboratory of Geoscience Spatial Information Technology |
He Z.,Chengdu University of Technology |
He Z.,Key Laboratory of Geoscience Spatial Information Technology |
And 4 more authors.
Yaogan Xuebao/Journal of Remote Sensing | Year: 2017
This paper reports on a method to improve the Ratio Of an Exponentially Weighted Averages (ROEWA) edge detector, so that the improved edge detector can accurately determine the positions and directions of edges for Synthetic Aperture Radar (SAR) images. We attempt to build an optimal edge detector for SAR images to obtain better results of edge detection. The edge strength index is redefined as an inverted, signed, and normalized minimum ROEWA (IROEWA), which is utilized to quantitatively describe the phase step of edges. A new method that accurately calculates edge direction is developed based on the edge strength map from IROEWA. We can obtain the possible values of edge directions in this manner, which continuously distributes from 0 degrees to 180 degrees. Therefore, we must improve the Non-Maximum Suppression (NMS) algorithm, so that it can process sub-pixels. Finally, the improved NMS algorithm is also added into the edge detection workflow. This improved edge detection algorithm is called IROEWA & NMS. We conducted two experiments for IROEWA & NMS: one employed nature SAR images, whereas the other adopted a simulation SAR image. Experiment results show that the IROEWA & NMS outperforms the original ROEWA with watershed thresholding. The IROEWA operator is faster than the ROEWA operator under the same conditions. We applied a Receiver Operating Characteristic (ROC) curve to evaluate the IROEWA & NMS and determined that its Area Under the Curve (AUC) is 0.97570; thus, it approximates the ideal optimal detector. The detection rate at the position of the optimal point in the ROC curve of the IROEWA & NMS is as high as 0.95232, whereas the false alarm rate is as low as 0.00214. The IROEWA & NMS exhibits suitable performance on both the detection and false alarm rates. It has significant application value in several fields, such as the segmentation and edge detection for SAR images. © 2017, Science Press. All right reserved.
Wang Q.,Chengdu University of Technology |
Zhang T.B.,Chengdu University of Technology |
Zhang T.B.,Key Laboratory of Geoscience Spatial Information Technology |
Yi G.H.,Chengdu University of Technology |
And 4 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2017
The Hengduan mountain area is acting as the essential ecological barrier for the upper reaches of the Yangtze River, which exerts profound influences to the climate and ecological environment of its surrounding areas as well as the Middle West part of our country. As the core of carbon budget climate changes, NPP functions as the crucial indicator in measuring the health status and sustainable development of the ecological system. Therefore, based on the NPP statistics of MODIS C6, vegetation map (1:1000000), meteorological data as well as topographic data, this paper is intended to utilize trend line analytical method and other related analysis methods to perform study on the spatial pattern, variation rules and the driving factors to NPP in Hengduan mountain area during year 2004—2014. Detailed research results indicate that: ① total NPP for Hengduan mountain area during 2004—2014 falls between 183.768—223.239 TgC with average of annual NPP total value as 208.498 TgC and annual NPP mean value per unit area as 463 gC m-2 a-1. On the whole, overall NPP is showing an increasing trend with distinct local disparity. ② average annual NPP change rate is within -53—97 gC m-2 a-1. And regions with a rising NPP tendency are mainly distributed at the north part, east of middle part as well as east and west of the south part; whereas regions with a decreasing tendency mainly concentrates on Wenchuan-Yingxiu areas which belong to the northwest and middle part. ③ The regions with NPP changes resulted from climate factors take up 8.42% of the total coverage of the Hengduan mountain area. These regions mainly sit at the mountainous areas at Daxue Mountain-Shaluli Mountain. By contrast, those subject to non-climate factors occupy 91.58% of the Hengduan mountain area. And they are mainly located at Aba areas in the north and broad regions in the south part with lower altitude. As far as the significance of this paper is concerned, it will provide instructions to the ecological environment construction and the sustainable growth for Hengduan mountain area. © 2017, Ecological Society of China. All rights reserved.
Yang X.,Chengdu University of Technology |
Yang X.,Sichuan Engineering Research Center for Emergency Mapping & Disaster Reduction |
Yang X.,Key Laboratory of Geoscience Spatial Information Technology |
Xu T.,Chengdu University of Technology |
And 7 more authors.
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2015
To overcome limits of traditional passive remote sensing data distribution methods, personalization is an inevitable trend of spatial information service. User profile is the basic foundation for personalized, active and accurate spatial information dissemination service, which can be used in the definition of users' preferences or interests of remote sensing data. In view of the coverage characteristics of remote sensing data in spatial and spectrum, this paper adopted the interval mathematics method into the representation of user profiles. Based on user profiles, the concepts of the correlation degree and interest degree are introduced. In addition, by the construction of decision matrixes, the solutions of the generations of intelligent services can be converted into the solutions of multiple attribute decision problems. Finally, an instance is given to show the usability of the presented method. © 2015, Surveying and Mapping Press. All right reserved.
Yi G.-H.,Geomathematics Key Laboratory of Sichuan Province |
Yi G.-H.,CAS Chengdu Institute of Mountain Hazards and Environment |
Ni S.J.,Chengdu University of Technology |
Zhang T.-B.,Geomathematics Key Laboratory of Sichuan Province |
And 3 more authors.
Journal of Chengdu University of Technology (Science and Technology Edition) | Year: 2015
This paper discusses the improvement of the system core theory used in the evaluation of geochemical anomalies. Three parameters of the system network graph are provided, including connectivity, connectivity coefficient and stability coefficient, to judge the overall stability of the system network graph and improve the stability evaluation method for the theory of system core. The method is used to analyzes the geochemical anomaly results of the Wulonggou gold deposit zone in Qinghai Province. In 29 combination anomalies (bands) of the region, 25 combination anomalies (bands) with gold prospecting potential have been screened. Among them, in 17 combination anomalies (bands), there are known gold deposits, and the coincident rate reaches 68%.
Shao H.,Chengdu University of Technology |
Shao H.,Key Laboratory of Geoscience Spatial Information Technology |
Liu M.,Chengdu University of Technology |
Liu M.,Key Laboratory of Geoscience Spatial Information Technology |
And 9 more authors.
Environmental Earth Sciences | Year: 2014
The Anning River Basin is located in the transitional zone of the Qinghai-Tibet Plateau, Yunnan-Kweichow Plateau and Sichuan Basin. This transitional zone is an important ecological barrier of the upper reaches of the Yangtze River and plays a significant role in the ecological security and ecological construction of Sichuan Province. However, the innate vulnerability of the eco-environment combined with the unreasonable development and use of minerals, hydropower, agriculture and animal husbandry resources contribute to prominent eco-environmental problems. In support of remote sensing and geographical information system, this study uses the spatial principal component analysis (SPCA) method to build the evaluation model for the vulnerability evaluation and analysis of the eco-environment in the Anning River Basin. The following indicators are selected for the SPCA: elevation, slope, vegetation index, land use, soil type, soil erosion, precipitation, temperature, and population density. Thereafter, the first four principal components are selected and their corresponding weights are determined. The eco-environmental vulnerability comprehensive index of the Anning River Basin is calculated by using these data. According to the calculated results, the eco-environmental vulnerability of the Anning River Basin is divided into five levels, namely, potential vulnerability, slight vulnerability, light vulnerability, moderate vulnerability, and high vulnerability. Eco-environmental changes for the past 20 years (from 1990 to 2010) are discussed and analyzed as well as the driving forces. The analysis shows that the eco-environmental vulnerability of the Anning River Basin is at the moderate level, and exhibits obvious vertical distribution characteristics. The main reasons that cause eco-environmental changes are mainly human factors, socioeconomic factors, and environmental protection policies like "Natural Forests Protection" and "Grain-for-Green". Based on the vulnerability classification results, the Anning River Basin is divided into three partitions for different degrees of eco-environmental reconstruction and protection, which provides foundation for the local eco-environmental reconstruction so as to reconstruct in order of the importance and urgency. © 2014 Springer-Verlag Berlin Heidelberg.
Xian W.,Chengdu University of Information Technology |
Xiang Z.,Key Laboratory of Geoscience Spatial Information Technology |
Liu L.,Key Laboratory of Geoscience Spatial Information Technology |
Shao H.,Key Laboratory of Geoscience Spatial Information Technology
Environmental and Engineering Geoscience | Year: 2015
Zoige County, China, represents a fragile sub-alpine rangeland eco-environment with a severe land desertification problem. This paper aims at detecting land desertification change in Zoige County over 15 years with quantitative remote-sensing techniques using multi-spectral imagery. Landsat images acquired in 1994 and 2009 were analyzed using the following methodology: (1) image pre-processing; (2) spectral mixture analysis (SMA) to obtain precise sub-pixel classification results of land cover; and (3) change vector analysis (CVA) to conduct a multi-temporal comparison process. Change detection results depict the land desertification conditions and vegetation re-growth conditions. In this way, we characterized the spatialtemporal change pattern of land desertification in Zoige County between 1994 and 2009. After categorizing ecological regions based on change detection results, we analyzed the driving factors of both land desertification conditions and vegetation re-growth conditions, finding out that grasslands under intense grazing pressure tend to suffer severe desertification, while topographic relief has an obvious influence on vegetation re-growth. Specific suggestions for each ecological region are proposed, which can assist the development of environmental restoration measures and environmental protection measures in Zoige County in an effective way. Furthermore, this methodology for monitoring land desertification could be carried out across neighboring counties or in other regions with similar sub-alpine rangeland and land desertification problems.
Li G.,Sichuan Third Surveying and Mapping Engineering Institute |
Ying G.,Sichuan Third Surveying and Mapping Engineering Institute |
Wen X.,Sichuan Third Surveying and Mapping Engineering Institute |
Chen J.,Sichuan Third Surveying and Mapping Engineering Institute |
And 2 more authors.
International Conference on Geoinformatics | Year: 2013
WorldView-2 image data is an important data source for general survey project of geographic national conditions in China. In this research, eight methods, namely Brovey, Ehlers, HPF, HIS, PCA, Wavelet, Pan-Sharpen and Gram-Schimdt were adopted to fuse panchromatic and multi-spectral images of WorldView-2. Qualitative analysis from the aspects of clarity, texture and tone, and quantitative evaluation from the aspects of standard deviation, information entropy, average gradient, deviation index, correlation coefficients, and spectral distortion degree had been done. The results show that the image distortion degree based on the transformation method of Pan-Sharpen is smaller, and meanwhile, the fused image can largely keep the spatial texture details of high-resolution panchromatic band, so it is a suitable method for fusion of WorldView-2 images. © 2013 IEEE.
Yi G.,CAS Chengdu Institute of Mountain Hazards and Environment |
Yi G.,Chengdu University of Technology |
Zhang T.,Chengdu University of Technology |
Zhang T.,Key Laboratory of Geoscience Spatial Information Technology
International Journal of Environmental Research and Public Health | Year: 2015
The Tibetan Plateau is a key area for research on global environmental changes. During the past 50 years, the climate in the Siling Co lake area has become continuously warmer and wetter, which may have further caused the increase in Siling Co lake area. Based on the Siling Co lake area (2003 to 2013) and climate data acquired from the Xainza and Baingoin meteorological stations (covering 1966 to 2013), we analyzed the delayed responses of lake area changes to climate changes through grey relational analysis. The following results were obtained: (1) The Siling Co lake area exhibited a rapid expansion trend from 2003 to 2013. The lake area increased to 2318 km2, with a growth ratio of 14.6% and an annual growth rate of 26.84 km2·year−1; (2) The rate of air temperature increase was different in the different seasons. The rate in the cold season was about 0.41 °C per ten years and 0.32 °C in hot season. Precipitation evidently increased, with a change rate of 17.70 mm per ten years in the hot season and a slight increase with a change rate of 2.36 mm per ten years in the cold season. Pan evaporation exhibited evidently decreasing trends in both the hot and cold seasons, with rates of −33.35 and −14.84 mm per ten years, respectively; (3) An evident delayed response of lake area change to climate change is observed, with a delay time of approximately one to two years. © 2015 by the authors; licensee MDPI, Basel, Switzerland.
Yi G.-H.,CAS Chengdu Institute of Mountain Hazards and Environment |
Yi G.-H.,Chengdu University of Technology |
Deng W.,CAS Chengdu Institute of Mountain Hazards and Environment |
Li A.-N.,CAS Chengdu Institute of Mountain Hazards and Environment |
And 2 more authors.
Journal of Mountain Science | Year: 2015
Changes in the lake areas of Xainza basin in the past 33 years (1976 to 2008) were studied using Landsat data from Multispectral Scanners (1973–1977), Thematic Mapper (1989–1992, 2007–2009), and Enhanced Thematic Mapper Plus (1999–2002). The results indicated that lakes in the study area evidently expanded from 1976 to 2008, with total expansion of 1512.64 km2. The mean annual air temperature presented an upward trend with certain fluctuations from 1966 to 2008. The air temperature rise rates in the cold season (0.31°C/10a) were higher than those in the hot season (0.24°C/10a), in the Xainza station example. Precipitation exhibited evident seasonal differences. Mean annual precipitation in hot season is 281.48 mm and cold season is 32.66 mm from 1966 to 2008 in study area. Precipitation in the hot season was the major contributor to the increase in annual precipitation. Grey relational analysis (GRA) was used to study the response of lake areas to climatic factors. The mean air temperature and precipitation were selected as compared series, and the lake areas were regarded as the reference series. The grey relational grade (GRG) between compared series and reference series were calculated through GRA. The results indicated that changes in lake areas were mainly affected by climatic factors in the hot season. Lakes in this region were classified into three grades, namely, Grades I, II, and III according to the recharge source and elevation. The GRGs of each series varied for different grade lakes: the area of Grade III lakes were the most relevant to the hot season factors, the GRGs of precipitation and air temperature were 0.7570 and 0.6606; followed by the Grade II lakes; Grade I lakes were more sensitive to the air temperature. © 2015, Science Press, Institute of Mountain Hazards and Environment, CAS and Springer-Verlag Berlin Heidelberg.