Land water, one of the important components of land cover, is the indispensable and important basic information for climate change studies, ecological environment assessment, macro-control analysis, etc. This article ...Land water, one of the important components of land cover, is the indispensable and important basic information for climate change studies, ecological environment assessment, macro-control analysis, etc. This article describes the overall study on land water in the program of global land cover remote sensing mapping. Through collection and processing of Landsat TM/ETM+, China's HJ-1 satellite image, etc., the program achieves an effective overlay of global multi-spectral image of 30 m resolution for two base years, namely, 2000 and 2010, with the image rectification accuracy meeting the requirements of 1:200000 mapping and the error in registration of images for the two periods being controlled within 1 pixel. The indexes were designed and selected reasonably based on spectral features and geometric shapes of water on the scale of 30 m resolution, the water information was extracted in an elaborate way by combining a simple and easy operation through pixel-based classification method with a comprehensive utilization of various rules and knowledge through the object-oriented classification method, and finally the classification results were further optimized and improved by the human-computer interaction, thus realizing high-resolution remote sensing mapping of global water. The completed global land water data results, including Global Land 30-water 2000 and Global Land 30-water 2010, are the classification results featuring the highest resolution on a global scale, and the overall accuracy of self-assessment is 96%. These data are the important basic data for developing relevant studies, such as analyzing spatial distribution pattern of global land water, revealing regional difference, studying space-time fluctuation law, and diagnosing health of ecological environment.展开更多
Land surface water(LSW) is one of the most important resources for human survival and development, and it is also a main component of global water recycling. A full understanding of the spatial distribution of land su...Land surface water(LSW) is one of the most important resources for human survival and development, and it is also a main component of global water recycling. A full understanding of the spatial distribution of land surface water and a continuous measuring of its dynamics can support to diagnose the global ecosystem and environment. Based on the Global Land 30-water 2000 and Global Land 30-water 2010 products, this research analyzed the spatial distribution pattern and temporal fluctuation of land surface water under scale-levels of global, latitude and longitude, continents, and climate zones. The Global Land 30-water products were corrected the temporal inconsistency of original remotely sensed data using MODIS time-series data, and then calculated the indices such as water area, water ration and coefficient of spatial variation for further analysis. Results show that total water area of land surface is about 3.68 million km2(2010), and occupies 2.73% of land area. The spatial distribution of land surface water is extremely uneven and is gathered mainly in mid- to high-latitude area of the Northern Hemisphere and tropic area. The comparison of water ratio between 2000 and 2010 indicates the overall fluctuation is small but spatially differentiated. The Global Land 30-water products and the statistics provided the fundamental information for analyzing the spatial distribution pattern and temporal fluctuation of land surface water and diagnosing the global ecosystem and environment.展开更多
Assuring the quality of land-cover data is one of the major challenges for large- area mapping projects. Although the use of geospatial knowledge and ancillary data in improving land-cover classification has been stud...Assuring the quality of land-cover data is one of the major challenges for large- area mapping projects. Although the use of geospatial knowledge and ancillary data in improving land-cover classification has been studied since the early 1980 s, mature methods and efficient supporting tools are still lacking. This paper presents a geospatial knowledge-based verification and improvement approach for global land cover(GLC) mapping at 30-m resolution. A set of verification rules is derived from three types of land cover and its change knowledge(natural, cultural and temporal constraints). A group of web-based supporting tools is developed to facilitate the integration of and access to large amounts of ancillary data and to support online data manipulation and analysis as well as collaborative verification workflows. With this approach, two 30-m GLC datasets(Globe Land-2000 and Globe Land-2010) were verified and modified. The results indicate that the data quality of Globe Land30 has been largely improved.展开更多
Listed by UNESCO in 1987 as a World Heritage site,the world-famous Ming Great Wall stretches several thousands of kilometers across northern China,and served as a massive military defensive system which in recent time...Listed by UNESCO in 1987 as a World Heritage site,the world-famous Ming Great Wall stretches several thousands of kilometers across northern China,and served as a massive military defensive system which in recent times has a unique historical,artistic and scientific value.Due to historical reasons and lack of advanced technologies,construction resources and conservation status of Ming Great Wall have not been investigated in any systematic manner;indeed,the extent of the Great Wall has not even been measured.This has resulted in a shortage of reliable first-hand scientific information on actual size,spatially resource distribution and preservation status of this World Heritage site.Driven by the urgent need to establish protection,research,renovation and management of Ming Great Wall,a comprehensive investigation and spatial mapping was jointly organized and completed by the State Bureau of Survey and Mapping and State Administration of Culture Heritage.High resolution digital stereo models at 1:10000 map scale covering the whole length of the Ming Great Wall have been created by photogrammetric reconstruction using nearly ten thousand aerial images.Spatial distribution and attributes of the wall sections,trenches and various subsidiary facilities in the surroundings of the Great Wall were measured with the help of digital photogrammetry workstations and results from field studies.Reliable and precise information about the Ming Great Wall has now been obtained and documented,including surface lengths,resource distribution,and preservation status.For example,the total length of Ming Great Wall is 8851.8 km,of which 6259.6 km is of actual wall,2232.5 km of natural terrain,and 359.7 km of trenches.In category lengths,1828.8 km is constructed of stone,3411.3 km of earth,249.6 km in brick,197.5 km of cliff wall and the rest 572.4 km of other means.Such information provides the scientific basis and strong platform in helping to delineate areas needing protection,in planning conservation and renovation programs,as well as digital archiving for posterity and web-based applications for modern promotions of one of the world's great attractions,the Ming Great Wall.展开更多
基金supported by the National High-Tech R&D Program of China(Grant Nos.2009AA122003 and 2009AA122001)
文摘Land water, one of the important components of land cover, is the indispensable and important basic information for climate change studies, ecological environment assessment, macro-control analysis, etc. This article describes the overall study on land water in the program of global land cover remote sensing mapping. Through collection and processing of Landsat TM/ETM+, China's HJ-1 satellite image, etc., the program achieves an effective overlay of global multi-spectral image of 30 m resolution for two base years, namely, 2000 and 2010, with the image rectification accuracy meeting the requirements of 1:200000 mapping and the error in registration of images for the two periods being controlled within 1 pixel. The indexes were designed and selected reasonably based on spectral features and geometric shapes of water on the scale of 30 m resolution, the water information was extracted in an elaborate way by combining a simple and easy operation through pixel-based classification method with a comprehensive utilization of various rules and knowledge through the object-oriented classification method, and finally the classification results were further optimized and improved by the human-computer interaction, thus realizing high-resolution remote sensing mapping of global water. The completed global land water data results, including Global Land 30-water 2000 and Global Land 30-water 2010, are the classification results featuring the highest resolution on a global scale, and the overall accuracy of self-assessment is 96%. These data are the important basic data for developing relevant studies, such as analyzing spatial distribution pattern of global land water, revealing regional difference, studying space-time fluctuation law, and diagnosing health of ecological environment.
基金supported by the National High-Tech Research Program of China(Grant Nos.2009AA122001 and 2009AA122004)
文摘Land surface water(LSW) is one of the most important resources for human survival and development, and it is also a main component of global water recycling. A full understanding of the spatial distribution of land surface water and a continuous measuring of its dynamics can support to diagnose the global ecosystem and environment. Based on the Global Land 30-water 2000 and Global Land 30-water 2010 products, this research analyzed the spatial distribution pattern and temporal fluctuation of land surface water under scale-levels of global, latitude and longitude, continents, and climate zones. The Global Land 30-water products were corrected the temporal inconsistency of original remotely sensed data using MODIS time-series data, and then calculated the indices such as water area, water ration and coefficient of spatial variation for further analysis. Results show that total water area of land surface is about 3.68 million km2(2010), and occupies 2.73% of land area. The spatial distribution of land surface water is extremely uneven and is gathered mainly in mid- to high-latitude area of the Northern Hemisphere and tropic area. The comparison of water ratio between 2000 and 2010 indicates the overall fluctuation is small but spatially differentiated. The Global Land 30-water products and the statistics provided the fundamental information for analyzing the spatial distribution pattern and temporal fluctuation of land surface water and diagnosing the global ecosystem and environment.
基金funded by the National Natural Science Foundation of China (Grant No. 41231172)the Special Fund for Surveying, Mapping and Geoinformation Scientific Research in the Public Welfare (Grant No. 201512028)National High-Tech R&D Program of China (Grant No. 2013AA122802)
文摘Assuring the quality of land-cover data is one of the major challenges for large- area mapping projects. Although the use of geospatial knowledge and ancillary data in improving land-cover classification has been studied since the early 1980 s, mature methods and efficient supporting tools are still lacking. This paper presents a geospatial knowledge-based verification and improvement approach for global land cover(GLC) mapping at 30-m resolution. A set of verification rules is derived from three types of land cover and its change knowledge(natural, cultural and temporal constraints). A group of web-based supporting tools is developed to facilitate the integration of and access to large amounts of ancillary data and to support online data manipulation and analysis as well as collaborative verification workflows. With this approach, two 30-m GLC datasets(Globe Land-2000 and Globe Land-2010) were verified and modified. The results indicate that the data quality of Globe Land30 has been largely improved.
文摘Listed by UNESCO in 1987 as a World Heritage site,the world-famous Ming Great Wall stretches several thousands of kilometers across northern China,and served as a massive military defensive system which in recent times has a unique historical,artistic and scientific value.Due to historical reasons and lack of advanced technologies,construction resources and conservation status of Ming Great Wall have not been investigated in any systematic manner;indeed,the extent of the Great Wall has not even been measured.This has resulted in a shortage of reliable first-hand scientific information on actual size,spatially resource distribution and preservation status of this World Heritage site.Driven by the urgent need to establish protection,research,renovation and management of Ming Great Wall,a comprehensive investigation and spatial mapping was jointly organized and completed by the State Bureau of Survey and Mapping and State Administration of Culture Heritage.High resolution digital stereo models at 1:10000 map scale covering the whole length of the Ming Great Wall have been created by photogrammetric reconstruction using nearly ten thousand aerial images.Spatial distribution and attributes of the wall sections,trenches and various subsidiary facilities in the surroundings of the Great Wall were measured with the help of digital photogrammetry workstations and results from field studies.Reliable and precise information about the Ming Great Wall has now been obtained and documented,including surface lengths,resource distribution,and preservation status.For example,the total length of Ming Great Wall is 8851.8 km,of which 6259.6 km is of actual wall,2232.5 km of natural terrain,and 359.7 km of trenches.In category lengths,1828.8 km is constructed of stone,3411.3 km of earth,249.6 km in brick,197.5 km of cliff wall and the rest 572.4 km of other means.Such information provides the scientific basis and strong platform in helping to delineate areas needing protection,in planning conservation and renovation programs,as well as digital archiving for posterity and web-based applications for modern promotions of one of the world's great attractions,the Ming Great Wall.
