A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were u...A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.展开更多
Based on the Nansha coral islets and reef's time-space attributes,and the intension and extension of the remote sensing information, the concept model and concept system of coral islets and reef are proposed.Then ...Based on the Nansha coral islets and reef's time-space attributes,and the intension and extension of the remote sensing information, the concept model and concept system of coral islets and reef are proposed.Then twin-tree remote sensing information model for different kinds of reef is constructed by using abstracted islets and reef's primitive, and the structure recognition system for coral islets and reef type is developed.展开更多
Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the N...Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.展开更多
The results of paleogeomagnetics and geo-chemistry of the coral reef in well Nanyong 2 of Nansha Is-lands showed that the bottom of the black sedimentary in-terlayer corresponds to the conversion boundary line be-twee...The results of paleogeomagnetics and geo-chemistry of the coral reef in well Nanyong 2 of Nansha Is-lands showed that the bottom of the black sedimentary in-terlayer corresponds to the conversion boundary line be-tween Brunhes Postive Polarity and Matuyama Reversed Polarity (B/M) and the cold/warm (19/20) climatic conver-sion bounds on ()18O curve, 0.78 Ma ago; and the red sedi-mentary interlayer corresponds to the Reunion I polarity excursion (reversion) of the geomagnetic field, 2.01-2.04 Ma ago. Comparing with the normal light-coloured coral reef rock, the magnetic susceptibility (x), residual magnetization intensity (Mr) and the content of MnO and Fe2O3 of the black sedimentary layer appeared obviously positive ab-normity. The magnetic susceptibility (x), residual magnetiza-tion intensity (Mr) and the content of Fe2O3 of the red sedi-mentary layer also appeared positive abnormity. Combining with the analyzing results of paleontology, we hold that this pair of special and typical sedimentary展开更多
基金The National High Technology Research and Development Program of China(863 Program)under contract No.2012AA12A406the National Natural Science Foundation of China under contract Nos 41471068,41171325,and J1103408+1 种基金the Program for New Century Excellent Talents in University under contract No.NCET-12-0264the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘A detailed survey of the reefs in the Nansha Islands＇ sea that are of strategic importance is conducive to their future development. In this study, a total of 50 Landsat 8 operational land imager（OLI） images were used to analyze the geological features and spectral characteristics of the Nansha reefs. The exposed islands/sandbanks,reef flats and sub-tidal reefs were identified with the near-infrared band, the red and green bands, and the blue band, respectively. Based on the relationships among various characteristics and bands illustrated in the OLI images, the maximum between-cluster variance threshold algorithm（OTSU method） and the mathematical morphology were employed to extract characteristic parameters of the spatial geometry of the reefs from top to bottom, which were subsequently operated by a series of post-processing methods such as vectorization,simplification and topological analysis. Among the 132 standalone reefs and 16 atolls that are identified in the study, four reefs have yet to be named in the Standard Names of Various Islands in the South China Sea and the website Nansha Islands Online（http：//www.nansha.org/）. Another 24 ones are exposed to the atmosphere even during high tides. Taiping Island with an area of 0.57 km^2 represents the largest exposed geological feature. This study demonstrated the applicability of medium-resolution satellite images to derive the coral reef information effectively and thus provided information for the related departments that are responsible to manage the coast.An improved resolution of multispectral bands with the panchromatic band in higher spatial resolution（15 m for OLI image） is expected to provide an optimum satellite based approach to map marine habitats.
文摘Based on the Nansha coral islets and reef's time-space attributes,and the intension and extension of the remote sensing information, the concept model and concept system of coral islets and reef are proposed.Then twin-tree remote sensing information model for different kinds of reef is constructed by using abstracted islets and reef's primitive, and the structure recognition system for coral islets and reef type is developed.
文摘Based on the remote sensing information feature of Nansha coral islets and reefs that controlled by the Nansha Islands local area's goological structure and growth law, by means of mathematical model and PC, the Nansha Islands coral islets and reefs' top geological data' spatial distribution and local change trend are simulated by using the trend surface system on the remote sensing composite information, and an scientific interpretation and local comparison of Nansha coral islands and islets' spatial distribution feature are made.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 49806002) the Key Project of the Chinese Academy of Sciences (Grant No. KZ951-B1-406-04) the Test Foundation of Guangzhou Branch of the Chinese Academy of Science
文摘The results of paleogeomagnetics and geo-chemistry of the coral reef in well Nanyong 2 of Nansha Is-lands showed that the bottom of the black sedimentary in-terlayer corresponds to the conversion boundary line be-tween Brunhes Postive Polarity and Matuyama Reversed Polarity (B/M) and the cold/warm (19/20) climatic conver-sion bounds on ()18O curve, 0.78 Ma ago; and the red sedi-mentary interlayer corresponds to the Reunion I polarity excursion (reversion) of the geomagnetic field, 2.01-2.04 Ma ago. Comparing with the normal light-coloured coral reef rock, the magnetic susceptibility (x), residual magnetization intensity (Mr) and the content of MnO and Fe2O3 of the black sedimentary layer appeared obviously positive ab-normity. The magnetic susceptibility (x), residual magnetiza-tion intensity (Mr) and the content of Fe2O3 of the red sedi-mentary layer also appeared positive abnormity. Combining with the analyzing results of paleontology, we hold that this pair of special and typical sedimentary
