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101.
Coral reefs are an sensitive-to-environment complex marine ecosystem. The ecosystem of corals is rich in biodiversity. Remote sensing offers a powerful tool for categorizing coral reefs and is the most cost-effective approach for the large-scale reef survey. The Dongsha Atoll, more than 300 km2 with an average depth of 10 m, is located at the northern continental margin of the South China Sea. It has been abused by destructive fishing during recent decades. Three satellite imageries (Quickbird2, ETM and SPOT5) are used to evaluate the capabilities of SPOT5 imagery to provide data that are useful for categorizing the current distribution of coral reefs therein. During the data processing, unsupervised classification functions are adopted for ETM and SPOT5 data, while the supervised classification method is used for Quickbird2. The classes are (or not) merged into coral reef, and then will be operated by vectorization, simplification, and topological analysis. There are 1 331 coral reefs larger than 100 m2 with a detection limit of 3×3 pixels at the multi-band data of Quickbird2, which is taken as the comparison baseline. The results extracted from SPOT5 and ETM images are less in number and area than those from the Quickbird2 image, whereas the results from SPOT5 data are better than those of ETM data at the silty lagoon due to its higher resolution. SPOT5 XS band 2 fails to distinguish the deep substrate inside the atoll compared with ETM data because of its poor penetration capability. Only SPOT XS band 1 cannot be used to differentiate coral reef from sand bottom. Merging the SPOT5 multi-bands data with the spatial resolution of SPOT5 pan-data and referring to ETM imagery are expected to provide an optimal satellite-based approach for mapping of coral reefs. 相似文献
102.
以毛乌素沙地典型地区为例,以CBERS2、Landsat5 TM、SPOT5及 TM与SPOT5融合影像作为基本数据源,使用波谱角分类法对
该区流动沙地、半固定沙地、固定沙地和沙化耕地进行信息提取,探索和比较该方法针对不同传感器遥感影像的沙化信息提取精度
。对本研究区,不同传感器影像的沙化信息提取精度均在80%以上,其中融合影像的沙化信息提取精度最高为90.13%,SPOT5次之,
而CBERS2和TM对不同类型的沙化信息提取各有优势,但CBERS-2信息提取的精度要高于TM。这说明使用波谱角分类法提取的结果精
度与影像空间分辨率有正相关关系,即空间分辨率越高,沙化信息的提取精度也越高。 相似文献
103.
通过利用多种图像融合方法分别对航片数字化影像与SPOT5多光谱影像进行融合试验,经定量化指标评价结果表明,利用Pansharp,HPF和HIS融合方法计算后得出的影像在很大程度上保留了原多光谱影像的光谱特征,清晰度有较大提高,具有更强的解译和量测能力。 相似文献
104.
基于SPOT5 HRS严格成像模型,提出了一种新的严密的反变换算法,介绍了其求解过程,并利用某地区的数据验证了其可行性. 相似文献
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108.
中亚地区与中国西部同属一个完整的内陆地理生态系统,生态环境极其相似,基于丝绸之路经济带的区域间大发展,对中亚地区荒漠化的研究,将更好的服务于我国向中亚开放发展的战略。依据2000—2015年SPOT VEGETATION为数据源,引入像元二分模型法(DPM),得到2000—2015年间中亚地区的植被覆盖度数据,通过计算转换,最终获取4期中亚地区土地荒漠化程度分布图与荒漠化等级数据,并对其进行分析。结果表明:中亚地区荒漠化总体呈“7”字形分布,基本沿东北西南方向对称;中亚地区整体荒漠化情况不容乐观,荒漠化面积比例约占到中亚地区面积的80%;荒漠化有扩张趋势,2000—2010年,约以每年20 km的速度向北部扩张,但从2010—2015年以后增速明显放缓。总体来看,中亚西南部荒漠化程度依然在加剧。研究表明,基于遥感数据对中亚荒漠化问题的研究,可以有效弥补地面数据不足这一劣势,为以后大尺度的遥感制图提供数据支撑。 相似文献
109.
Time series analysis of optical remote sensing data for the mapping of temporary surface water bodies in sub-Saharan western Africa 总被引:2,自引:0,他引:2
A map of temporary small water bodies (TSWB) at 1 km resolution was derived for the arid, semi-arid and dry sub-humid regions of sub-Saharan western Africa where the spatio-temporal distribution of actual surface water occurrence exhibits high inter- and intra-annual variability. Water bodies and humid areas have been mapped and characterized by the analysis of 10 daily small water bodies (SWB) maps based on SPOT VEGETATION (VGT) data spanning the period January 1999–September 2007. Further analysis of the SWB time series provided additional information about the seasonal recurrence of water bodies as well as their hydrological function. A map derived from a continuous time series assures the inclusion of temporary features, a clear advantage compared to other datasets, which are based on several single date observations. The method described in this paper targets at a rapid creation of TSWB maps based on the SWB time series for different time intervals and regions.An accuracy assessment has been carried out with a stratified random sampling approach and a one-stage cluster analysis that relies on high-resolution satellite data to verify the detected water bodies. The overall accuracy, considering only the commission error, is 95.4% for the whole study region, with best results in the arid and semi-arid climate zone. The method to map water bodies delivers satisfactory results, particularly for sparsely vegetated areas as well as flat areas of the study region. In more humid, more vegetated areas and in mountainous areas, the possibility of false detections increases due to surface characteristics. 相似文献
110.
Detecting co-seismic displacements in glaciated regions: An example from the great November 2002 Denali earthquake using SPOT horizontal offsets 总被引:1,自引:0,他引:1
Michael H. Taylor Sebastien Leprince Jean-Philippe Avouac Kerry Sieh 《Earth and Planetary Science Letters》2008,270(3-4):209-220
We use SPOT image pairs to determine horizontal offsets associated with the Mw 7.9 November 2002 Denali earthquake in the vicinity of Slate Creek, AK. Field measurements and aerial photographs are used to further characterize the geometry of the surface rupture. Aerial photographs show that shear localization occurs where the rupture trace is linear, and distributed off-fault deformation is common at fault bends and step-overs, or at geologic contacts between rock, glacial sediments, and ice. The displacement field is generated using a sub-pixel cross correlation technique between SPOT images taken before and after the earthquake. We identify the effects of glacier motion in order to isolate the tectonic displacements associated with the Denali earthquake. The resulting horizontal displacement field shows an along-strike variation in dextral shear, with a maximum of approximately 7.5 m in the east near 144° 52′W, which decreases to about 5 m to the west near 145° 45′W. If the November 2002 earthquake represents the long-term behavior of the Denali fault, it implies a westward decrease in the long-term dextral slip rate. A possible mechanism to accommodate the westward decreasing slip on the Denali fault is to transfer fault slip to adjacent east-trending contractional structures in the western region of the central Alaskan Range. 相似文献