共查询到20条相似文献，搜索用时 31 毫秒
1.
Thara Nair Latha James C. V. Rao A. V. V. Prasad B. Gopala Krishna V. K. Dadhwal 《Journal of the Indian Society of Remote Sensing》2017,45(5):873-885
Coral reefs are one of the most diverse of all marine ecosystems and are often referred to as the “rainforests of the sea”. Though they cover less than one per cent of Earth’s surface, they are home to one quarter of all ocean species by providing food and shelter to them. Optical remote sensing has been widely employed for mapping and monitoring coral reefs. But the application of microwave remote sensing has been an alternate domain in this area. This study explores the possibility of utilizing synthetic aperture radar (SAR) data of Radar Imaging Satellite-I, India’s first indigenous microwave satellite to delineate the coral reefs in Andaman and Lakshadweep Islands in the Indian Ocean. The dual polarized data, after reducing the speckle has been classified to delineate the coral reefs in the vicinity of both islands. SAR has a performance comparable with passive optical sensors under favourable conditions of imaging, viz. optimum tidal current and surface winds. The study results are compared with the international coral reef reference map and are found to be highly promising, with an overall accuracy of 98.3% and a Kappa coefficient of 0.944 for fringing reefs in Andaman region. For the atolls in Lakshadweep region, the overall accuracy is found to be 92.99% and the Kappa coefficient is estimated at 0.7377. This study tries to explore a different horizon for microwave remote sensing in coral reef studies. It is seen that, optical and microwave remote sensing can provide a mutually supporting platform in coral reef delineation, in terms of imaging depth as well as climatic conditions. 相似文献
2.
R. Sridhar T. Thangaradjou L. Kannan S. Astalakshmi 《Journal of the Indian Society of Remote Sensing》2010,38(3):565-575
Coastal resources viz., coral reefs, seagrasses, mangroves, and coastal land features viz., sandy beach, mudflats and salt
pan/aquaculture ponds were classified and assessed in the Palk Bay region of the south-east coast of India using IRS LISS
III satellite image (1996, 2000, 2002 and 2004). The study recorded an areal coverage of 286.95 ha of reef area during 2004,
which is 177.54 ha lesser than that of the reef area of 1996. The reef vegetation composed mainly of seaweeds has gained over
29.44 ha during the same period. Likewise, sand over reef area has also increased alarmingly i.e. 120.34 ha between 1996 and
2004. The seagrass beds of Munaikkadu region of the Palk Bay are comparatively protected and have gained over 7.5 ha between
1996 and 2004. It has been found that both the dense (2.99 ha) and sparse (36.45 ha) mangroves have gained their areal coverage
considerably between 1996 and 2004. Whereas in Devipattinam region, many anthropogenic pressures are exerted only on the seagrass
resources which has led to the reduction of over 785.5 ha of dense seagrass beds between 1996 and 2004. The study clearly
indicated that the resources are under the pressures of low to high threats, especially the coral reefs and seagrasses, if
the pressures continue, coastal resources of the Palk Bay may face serious threats of destruction in this part of the Bay
in the years to come. 相似文献
3.
Shoreline and coral reef ecosystem changes in gulf of Mannar, Southeast coast of India 总被引：1，自引：0，他引：1
M. Thanikachalam S. Ramachandran 《Journal of the Indian Society of Remote Sensing》2003,31(3):157-173
Changes in shoreline, coral reef and seafloor have been mapped using remote sensing satellite data of IRS LISS-III (1998),
IRS LISS-II (1988), Survey of India Topographic sheet (1969), Naval Hydrographic Chart (NHO) 1975 and bathymetry data (1999)
with ARC-INFO and ARC-VIEW GIS. The analysis of multi-date shoreline maps showed that 4.34 and 23.49 km2 of the mainland coast
and 4.14 and 3.31 km2 areas of island coast have been eroded and accreted, respectively, in the Gulf of Mannar. The analysis of multi-date coral
reef maps showed that 25.52 km2 of reef area and 2.16 km2 of reef vegetation in Gulf of Mannar have been lost over a period of ten years. The analysis of multi-date bathymetry data
indicates that the depth of seafloor has decreased along the coast and around the islands in the study area. The average reduction
of depth in seafloor has been estimated as 0.51m over a period of twenty four years. The increased suspended sediment concentration
due to coastal and island erosion, and raised reef due to emerging of coast by tectonic movement are responsible for coral
reef degradation in the Gulf of Mannar. Validation by ground truth has confirmed these results. 相似文献
4.
Eco-Geomorphological zonation of The Bangaram Reef, Lakshadweep 总被引：1，自引：0，他引：1
Benidhar Deshmukh Anjali Bahuguna Shailesh Nayak V. K. Dhargalkar T. G. Jagtap 《Journal of the Indian Society of Remote Sensing》2005,33(1):99-106
Coral reefs, which are known for rich biological diversity and productivity, are being threatened throughout the world by various natural and anthropogenic activities. The present study concentrates on establishing methodology to zone the geo-morphological and ecological zones of the Bangaram reef (of atoll type), Lakshadweep islands, using remotely sensed data and adequately supported by field data. Classification system has been evolved to zone the reefs. Comparative studies have also been carried out using image processing techniques in order to establish the suitable technique for studying the Indian reefs. The IRS LISS III images representing three different tidal conditions of the period 1998-2000 were analyzed. The unsupervised classification of both the raw images as well as principal component images gave similar information. The classified product was subjected to contextual editing. Misclassification among various classes was found to increase with the increase in the depth of the water column present over the reef. The zones identified on the image are central deep lagoon, reef knolls (rising steeply from the central deep lagoon floor), reef edge, reef platform, coralline shelf, broad shallow sandy-bottomed lagoon, beach and two islets. The zonation has helped in getting information on the presence of live corals on the Bangaram reef. This kind of study is a valuable input in assessing the health of the reefs and its diversity. 相似文献
5.
H.B. Chauhan R.M. Dwivedi 《International Journal of Applied Earth Observation and Geoinformation》2008,10(2):181-1
Coastal zone assumes importance due to high productivity of ecosystems, man-made developmental activities, natural hazards and dynamic nature of the coast. As costal ecosystems are unique and fragile, understanding the impact of developmental activities on the sustainability of the coastal zone is very important. Remote sensing, because of repetitive and synoptic nature is an ideal tool for studying this. Time series data analyses for monitoring coastal zone require different type of sensors. Present study deals with atmospheric correction of satellite data, reflectance, selection of coastal features like, mudflat, mangroves, vegetated dune, coastal water, etc. and their inter-comparison using different sensor data of RESOURCESAT sensors. Reflectance values give better separateability for various coastal features in comparison to DN values. LISS IV can be used in place of LISS III or merged (LISS III + PAN) for long-term coastal zone studies. 相似文献
6.
Abstract Coastal Tropism is a worldwide phenomenon. It induces urgent needs for observation inventories and management of coastal environment, mainly in developing countries. High resolution satellite data may solve some aspects of the problems. Three examples based upon the potential use of shrimp aquaculture sites in tropical salt marshes, the biotopes mapping in coral reef environments for biologic stock assessments and the characterization and quantification of evolutive stages of coral platforms, are developed. All three are relative to the same tropical Pacific Island with respect, for the first and second examples, to actual needs for the management of mangroves and coral reefs and for the third, to a scientific approach related to evolutive theory of reefs platforms in lagoons. Methodology and results based upon digital image processing and computer assisted photointerpretation are exposed. New trends in digital processing and associated digital cartography are listed. 相似文献
7.
A global inventory of coral reef stressors based on satellite observed nighttime lights 总被引：1，自引：0，他引：1
In this article, we present a satellite-based approach to gather information about the threat to coral reefs worldwide. Three chosen reef stressors – development, gas flaring and heavily lit fishing boat activity – are analysed using nighttime lights data derived from the Defense Meteorological Satellite Program (DMSP) produced at the National Oceanic & Atmospheric Administration, National Geophysical Data Center (NOAA/NGDC). Nighttime lights represent a direct threat to coral reef ecosystems and are an excellent proxy measure for associated human-caused stressors. A lights proximity index (LPI) is calculated, measuring the distance of coral reef sites to each of the stressors and incorporating the stressor's intensity. Colourized maps visualize the results on a global scale. Area rankings clarify the effects of artificial night lighting on coral reefs on a regional scale. The results should be very useful for reef managers and for state administrations to implement coral reef conservation projects and for the scientific world to conduct further research. 相似文献
8.
A study was conducted in Lakshadweep islands to determine the feasibility of using Indian Remote Sensing (IRS) satellites for detecting changes in the seagrass from other coastal features. IRS ID and IRS P6 LISS III having spatial resolution of 23.5 m with lower cost compared to all other contemporary satellites with the same spatial resolution have not been widely used for monitoring the changes in seagrass cover. In this context, the present study attempted to explore the effectiveness of LISS III data for mapping seagrasses and to inform the international community about the usefulness of these low-cost imageries for coastal resource monitoring. Supervised classification and change detection studies found a significant decrease in seagrass cover of 73.03 ha in the Lakshadweep group of islands. An overall accuracy of 67.5% was obtained for the change maps, and seagrass cover and its changes vary at different islands. 相似文献
9.
E. P. Nobi E. Dilipan K. Sivakumar T. Thangaradjou 《Journal of the Indian Society of Remote Sensing》2012,40(3):467-481
Seagrasses ecosystems are fragile yet highly productive ecosystems of the world showing declining trend throughout the world due to natural and anthropogenic pressures. Effective conservation and management plan is thus required to protect these resources, to aid with conservation need mapping and monitoring of seagrasses using high resolution remote sensing data is very much required. Hence, the present study was made to record the seagrass aerial cover in the Lakshadweep islands using IRS P6 LISS IV satellite data. The suitability of LISS IV sensor for seagrass mapping was tested for the first time with an overall accuracy of 73.16%. The study found an area of 2590.2?ha of seagrasses in Lakshadweep islands with 1310.8?ha and 1279.4?ha dense and sparse seagrass cover respectively. The study recommends the use of LISS IV data for mapping the shallow water seagrasses, as mapping efficiency increases nearly 4 times more than the LISS III data, as the former (LISS IV) picks up the small patches of seagrasses and delineates the coral and reef vegetation patches from seagrass class. 相似文献
10.
珊瑚礁遥感研究进展 总被引：1，自引：0，他引：1
珊瑚礁是生物多样性和初级生产力最高的海洋生态系统之一,对人类社会与海洋生态环境的健康和可持续发展有重要作用,而珊瑚礁又是中国南海主要的国土类型,国家因此越来越重视对南海珊瑚礁的规划、管理、建设与保护。珊瑚礁的调查与探测则是进行珊瑚礁活动的基础与依据,而遥感则在珊瑚礁的大范围探测方面具有很大的潜力,所以国内外已经存在很多利用遥感对珊瑚礁进行调查与探测的研究与应用。本文将按照被动遥感和主动遥感的顺序,客观地阐述国内外珊瑚礁遥感研究与应用的进展,探讨珊瑚礁遥感研究与应用的发展趋势,并尝试总结中国珊瑚礁遥感的机遇和挑战。其中被动遥感包括珊瑚礁地形与水深的遥感、珊瑚礁底质与地貌的遥感、珊瑚礁岸线变化与稳定性的遥感以及珊瑚礁环境的遥感等,而主动遥感则包括珊瑚礁水深的机载激光雷达遥感、珊瑚礁地貌的船载声学遥感和珊瑚礁地形的星载微波遥感等。结果发现,国内珊瑚礁遥感研究与应用的整体水平落后于国外:虽然在部分数据处理方面具有比国外更先进的技术,但相应的应用基础研究仍然达不到国外的广度与深度。因此,国内的珊瑚礁遥感研究仍需要鼓励珊瑚礁学者更多的参与与合作,以便在硬件设备和数据处理等方面加强针对珊瑚礁遥感的研究,进而融合多种手段而实现珊瑚礁遥感的工程化应用。 相似文献
11.
C. J. Thampi 《Journal of the Indian Society of Remote Sensing》1983,11(1):23-29
The paper discusses the use of Remote Sensing techniques for the integrated economic land use planning in Andaman and Nicobar Islands, agricultural land use being the main objective. Broad aspects of physiography, soil, land use etc. have been described. An idea about the soil environment and erosion hazards is given. A land use pattern on the basis of land capability and land suitability classification together with cropping pattern has been evolved and the model has been developed for the Island. 相似文献
12.
Photogeomorphic studies of the Andaman coast reveal several landforms suggestive of coastal emergence and submergence in the recent past. Elevated reefel terrace, planation surfaces and escarpments indicate that the west coast is rising associated with a corresponding tilt of the islands in general to the east. Offshore structures in the west coast shelf and a few exposed structures in the main land are recommended for future exploration. 相似文献
13.
船载水陆一体化综合测量系统研究进展 总被引：3，自引：1，他引：2
海岛、海岸带等水陆结合部一直是开展海洋测绘的困难区域。近年出现的机载激光测深技术尽管可应用于海岸带、海岛礁等区域的测量，但由于受限因素较多，未能实现我国大部分水陆地形的无缝拼接工作。船载水陆一体化综合测量技术通过多进程网络技术集成三维激光测距、多波束测深、定位定姿等技术，弥补了传统测量方式低效率、高成本、获取水陆高密度的三维空间地理信息困难等不足，作为新兴的海洋空间探测技术优势明显。本文概述了目前国内外船载水陆一体化综合测量系统的最新研究进展，并对系统组成及原理进行了介绍，同时总结了系统的数据采集、处理流程中的关键环节及存在的问题，最后展望了其未来的发展趋势。 相似文献
14.
M. Sambasiva Rao 《Journal of the Indian Society of Remote Sensing》1982,10(3):23-30
An area of about 7500 km2 covering Cauvery delta has been studied from airphotos (1:60,000), Landsats (1:250,000) and survey of India topographic sheets (1:50,000) with a view to delineate various landforms, soils, land use, hydromorphic units, drainage, and flood intensity of the delta. The delta is composed of mainly ancient channels, delta p ains, fossil islands, levees, beach ridges, mangroves marshes and coastal dunes. The various soil types are clayey soils, silty soils, silty loams, sandy loams, coastal sands and alkaline clays. Paddy and sugarcane are dominant crops. The old channels are found to be zones of high ground water potential. The growth of delta seems to be from south to north with twelve abandoned meander lobes and three delta fronts with gradual influx of material into Bay of Bengal. The old rivet courses lying parallel to the present active Coleroon river in third stage of the growth of the delta seem to be severely affected by floods. Moderate to low growth is noticeable in the second stage of the of the delta. The oldest river course which debouched into Bay of Bengal near Adirama-patnam is less affected by floods. The delta plains, fossil islands, disturbed ridges and beach ridges are unaffected. Basing on landforms, soils, land use, hydrogeomorphology and flood intensity the land capability of the delta has been evaluated. About seven classes of land are interpreted. 相似文献
15.
The world’s largest mangrove ecosystem, the Sunderbans is experiencing multidimensional threats of degradation. The present study was aimed to understand these problems and search for proper remedies by applying suitable remote sensing technologies. South-western parts of Indian Sunderbans Biosphere Reserve had been chosen for assessment of land use/land cover changes in between 1975 and 2006 by using multitemporal Landsat data. Results indicated considerable reduction of open mangrove stands and associated biodiversity mainly in the forest-habitation interference zones of Sunderbans. On the contrary, increase in the coverage of dense mangroves in the reserved forests had been observed indicating the existence of proper centralized management regimes. Overall, a cumulative loss of approximately 0.42% of its original mangrove cover in between 1975 and 2006 had been estimated for this part of the Sunderbans which was at parity with the findings of other studies in the Sunderbans or similar mangrove ecosystems of the tropics. Expansion of non agricultural lands in the last two decades was found to be related with the growth of new settlements, tourism infrastructure, and facilities. This transformation was attributed to the shifting of local peoples’ interest from traditional forestry and subsistence farming towards alternative occupations like shrimp culture, coastal tourism, and commercial fishing although environmentally hazardous livelihood activities like collection of prawn seeds along the riverbanks were still persistent. 相似文献
16.
海岸带潮汐模型支持下的光束法区域网空中三角测量 总被引：1，自引：0，他引：1
针对海岸带和海岛(礁)稀少控制区域的摄影测量定位问题,结合海道测量学理论,提出了一种潮汐模型支持下的光束法区域网空中三角测量方法。该方法首先根据摄影时间利用精密潮汐模型计算摄影瞬间水边线上各点的高程值,然后引入水边线上这些高程已知的点,和其他控制点以及连接点一起参加平差,精确确定摄影时影像的空间方位。实验表明,该方法能够提高海岸带和海岛(礁)稀少控制区域岛(礁)、滩涂等要素的几何定位精度。 相似文献
17.
M. G. Shaikh Shailesh Nayak P. N. Shah B. B. Jambusaria 《Journal of the Indian Society of Remote Sensing》1989,17(1):41-48
Landsat TM data was utilised for coastal geomorphic mapping around the Gulf of Khambhat. Various landforms like shoreline, estuaries, mudflats, islands, mangroves, relict aluvium, cliffs, dunes, flood plains, paleochannel, paleomeanders, oxbow lake, etc. were delineated. The estuaries were divided into salt-wedge estuary, fully mixed estuary and partially mixed estuary based on amount of freshwater discharge and nature of tidal currents. The mudflats were classified into high tide flats, intertidal slopes and subtidal zones. These classes were further classified based on their composition. It was concluded that TM data has broughtout many new features and improved the classification of coastal landforms. The presence of coastal features like drowned river valleys, paleomudflats, relict alluvium, dunes, paleomeanders, oxbow lake and terraces clearly indicate the sea-level changes of the Quarternary period. 相似文献
18.
科学准确地监测红树林是保护海陆过渡性生态系统的基础和前提,但红树林分布于潮间带,难以进行大规模人工监测。遥感技术能够对红树林进行长时间、大面积监测,但已有研究尚存不足。一方面,红树林分布于热带、亚热带区域,受到天气条件限制难以获得长时间覆盖的有效光学遥感数据;另一方面,红树林极易与其他陆生植被混淆,仅利用多波段数据的光谱信息难以精确识别。本文以恒河三角洲孙德尔本斯地区为例,基于谷歌地球引擎GEE（Google Earth Engine）获取2016年全年的Landsat 8 OLI和Sentinel-2 MSI数据,利用物候信息进行红树林提取研究。首先,基于最小二乘回归构建两个传感器在相同指数之间的关系,重建时间序列数据,之后根据可分性判据选取增强型植被指数EVI（Enhanced Vegetation Index）和陆地表面水分指数LSWI（Land Surface Water Index）。其次,对两个指数的时间序列数据进行Savitzky-Golay滤波处理,并分别提取生长期始期等13种物候信息。最后,将两个指数的物候信息进行特征级联,采用随机森林RF（Random Forest）方法进行分类,提取研究区红树林范围。实验结果表明：Landsat 8 OLI和Sentinel-2 MSI数据融合可有效提升时间序列质量,与基于单一传感器数据的分类结果相比,总体精度提高1.58%;物候信息可以显著增强红树林与其他植被的可分性,与直接使用时间序列数据的分类结果相比,总体精度提高1.92%;同时考虑EVI和LSWI指数可极大地提升分类效果,与采用单一指数相比,总体精度分别提高14.11%和9.69%。因此,本文通过数据融合、物候信息提取和指数特征级联可以更好地提取红树林,总体精度达到91.02%,Kappa系数为0.892。研究验证了物候信息在红树林遥感监测中的应用潜力,提出的方法对科学准确地监测全球或区域红树林具有一定参考价值。 相似文献
19.
Kumar Arun Prasad Vaithilingam Selvam Ramasamy Ramasubramanian Chandra Sekar Kar 《国际地球制图》2015,30(5):580-599
Development of a spectral library is a prerequisite for the higher order classification of satellite data and hyperspectral image analysis to map any ecosystem with rich diversity. In this study, sampling methodology, collection of field and laboratory spectral signatures and post-processing methodologies were investigated for developing an exclusive spectral library of mangrove species using hyperspectral spectroscopic techniques. Canopy level field spectra and leaf level laboratory spectra were collected for 34 species (25 true and 9 associated mangroves) from two different mangrove ecosystems of the Indian east coast. Post-processing steps such as removal of water vapour absorption bands, correction of drifts which occur due to the thermal properties of the instrument during data collection and smoothing of spectra for its further utilisation were applied on collected spectra. The processed spectra were then compiled as spectral library. 相似文献
20.
Anup Kumar Das Saumitra Mukherjee 《Journal of the Indian Society of Remote Sensing》2002,30(3):149-156
In the present study an attempt has been made in order to evaluate the weathering and erosional status of a part of the Konkan coast stretching between Mumbai and Rajpuri, using IRS-IB, LISS-II data supported by spectral reflectance and thin section study of the rock samples collected from the coastal plains. The study revealed that extensive erosion has been taking place in few pockets along the Konkan Coastal plain, which is evidenced by the presence of more weathered rocks in the coastal plains as compared to that of the hinterland, siltation of the coastal wetlands due to the deposition of eroded materials and high-suspended sediments in the coastal water. The thin section study of the basaltic rock samples collected from the coast also shows evidence of physical and chemical weathering. The lineaments of the coastal tract are found to exist in clusters mostly trending towards NNE—SSW and a few N—S trending, this supports the presence of a N-S trending fault parallel to the Konkan coast along the Western Ghats. It has also been found that remote sensing, in association with other conventional techniques is ideal for such type of studies. 相似文献