Method for UAV-based 3D topography reconstruction of tidal creeks     

ZHANG Xuhui  LI Huan  GONG Zheng  ZHOU Zeng  DAI Weiqi  WANG Lizhu  Samuel DARAMOLA 《地理学报(英文版)》2021,31(12):1852-1872

It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle(UAV) photogrammetry,but this method is not applicable in tidal creeks.The residual water will lead to inaccurate depth inversion results,and the topography of tidal creeks mainly de-pends on manual survey.The present study took the tidal creek of Chuandong port in Jiangsu Province,China,as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide.It also proposed a Trend Prediction Fitting (TPF) method for the topography of the unexposed part below the water to obtain a complete 3D topography.The topography above the water measured by UAV has the vertical precision of 12 cm.When the TPF method is used,the cross-section should be perpendicular the central axis of the tidal creek.A polynomial function can be adapted to most shape of sections,while a Fourier function obtains better results in asym-metrical sections.Compared with the two-order function,the three-order function lends itself to more complex sections.Generally,the TPF method is more suitable for small,straight tidal creeks with clear texture and no vegetation cover.  相似文献   

生物土壤结皮固沙理论与实践   总被引：3，自引：2，他引：1  

周晓兵  张丙昌  张元明 《中国沙漠》2021,41(1):164-173

生物土壤结皮是由土壤微生物、藻类、地衣和苔藓等孢子植物类群与土壤颗粒形成的有机复合体,在全球干旱区地表广泛分布,是干旱地表生物覆被层的主要构建者。生物土壤结皮是荒漠植物群落演替的先锋类群,能够提高荒漠地表的稳定性,固定碳和氮等营养元素,增加土壤肥力,并在保持土壤水分方面发挥重要作用,因此在干旱区受损地表的生态修复方面具有广阔的应用前景。通过分析组成生物土壤结皮的物种更替与维持其结构的胶结方式转变之间的生态关系,阐释了生物土壤结皮固沙的生物学基础,提出在人工结皮恢复实践中,应选择以本地优势物种（如具鞘微鞘藻、齿肋赤藓和银叶真藓等）为目标种的生态学原则,并通过对目标物种的纯化、培养,完成由实验室至温室的扩繁过程,实现逐级扩大生产,为野外固沙应用提供充足种源。阐述了结皮野外接种恢复的最适物种组成、物理化学方式结合的组合模式,提出应从地表稳定性、土壤养分和结皮物种多样性等方面进行生长状况评估,梳理了中国在结皮人工恢复领域的研究进展和面临的问题与挑战,阐释了利用人工培养生物土壤结皮开展生态修复的应用前景。  相似文献   

广州城区晚全新世环境变迁与人类活动     

李嘉欣  郑卓  谷俊杰  马婷  易西兵  汤永杰 《热带地理》2021,41(1):67-81

对广州市越秀区解放中路考古遗址剖面进行了年代学、岩性、硅藻和软体动物鉴定等研究,发现广州珠江北岸古城区南部在先秦时期为河道及河口湾湿地/洼地;因河流-河涌的淡水注入使河口盐度降低,故而沉积物中未见较高盐度的微体生物,仅发现了河口型咸水-半咸水硅藻;此时堆积的贝壳大多为淡水种,半咸水种少见,表明先秦（东周）时期,广州地区水域盐度与中全新世海湾环境完全不同。东周时期珠江两岸为河流淡水影响为主、与上溯潮水交汇的微咸水或淡水环境;地层中出土的大量淡水-微咸水贝壳,经AMS¹⁴C测年归于早于2500年前的渔猎文化盛行时食用废弃堆积,其后又被挖掘再堆填到后期的文化堆积中（如唐代城市扩张及清挖河涌）。秦至唐代该地逐渐成为人类频繁活动的地点,但仍为河流—潮汐相互影响下的洼地或河涌低地环境,与历史记录的唐代珠江岸线分布基本一致。宋代以后该区域已经暴露地表,并逐渐成为古代广州城区,期间可能受到多次洪水冲积。上述变化主要与全新世海平面变化、河流泥沙输入、土地利用与围垦等多方面影响有关,这些考古记录与广州古城演变吻合,与珠江三角洲地区晚全新世海退,以及平原淤积发展过程密切相关。  相似文献   

地铁对服务业集聚的影响——以广州市为例     

朱洪平  朱文涛  郑荣宝 《热带地理》2021,41(1):114-123

以广州市为例,基于POI数据,运用SAR模型识别城市地铁开通对服务业集聚的影响。研究发现：服务业集聚具有显著的空间依赖性特征,本地服务业集聚会受到周边地区服务业集聚的影响;开通地铁对广州市服务业空间集聚产生显著的正向影响,可提高城区的服务业集聚水平,但这种集聚效应因行业不同而有所差异;地铁开通对批发与零售业、住宿与餐饮业等生活性服务业的影响要高于其他服务业行业,但对科学研究和技术服务业集聚的影响并不显著;开通地铁对服务业集聚的影响还受到所在区域经济发展水平的影响,经济发展水平较高的区域,地铁对服务业集聚的提升作用较明显;而地铁换乘站对服务业集聚的影响要高于非换乘站。最后,建议完善城市地铁网络,加强地铁站点的基础设施配套,提高地铁网络密度和地铁站点间的空间距离以进一步发挥地铁对服务业集聚作用。  相似文献   

Gametogenesis and reproductive traits of the cold-seep mussel Gigantidas platifrons in the South China Sea     

Zhong  Zhaoshan  Wang  Minxiao  Chen  Hao  Zheng  Ping  Li  Chaolun 《中国海洋湖沼学报》2020,38(4):1304-1318

Gigantidas platifrons(Bivalvia,Mytilidae),the dominant species at the Formosa cold seep,relies on methanotrophic symbionts dwelling in its gills for nutrition.The reproductive patterns of G.platifrons provide fundamental information for understanding the population recruitment of this species.However,we know very little about important processes in reproduction,such as gametogenesis and symbiotic bacteria transmission.To this end,we described the developmental patterns of the gonads from nine surveys and juvenile length-distribution from one-year larval traps and detected bacteria in gonad from G.platifrons samples.Our results show that G.platifrons is a functionally dioecious species.The reproduction of G.platifrons is discontinuous,with spawning maturity peak around the fourth quarter of the year.The seasonal reproduction of G.platifrons was further supported by the unimodal shell length distribution of the trapped juvenile mussels.Given the small oocyte size(48.99-70.14 μm),which was comparable to that of coastal mussels,we proposed that G.platifrons developed via a free-living,planktotrophic larval stage before settlement.The blooms at the water surface can also supply the development of the planktonic larvae of G.platifrons.Meanwhile,no bacteria were observed in gonads,suggesting a horizontal symbiont transfer mode in this mussel.Collectively,these results provide fundamental biological information for an improved understanding of the early life history of G.platifrons in the Formosa cold seep.  相似文献   

Diffusion Characteristics of Swells in the North Indian Ocean     

Zheng  Chongwei  Liang  Bingchen  Chen  Xuan  Wu  Guoxiang  Sun  Xiaofang  Yao  Jinglong 《中国海洋大学学报(英文版)》2020,19(3):479-488

Research on the diffusion characteristics of swells contributes positively to wave energy forecasting, swell monitoring, and early warning. In this work, the South Indian Ocean westerly index(SIWI) and Indian Ocean swell diffusion effect index(IOSDEI) are defined on the basis of the 45-year(September 1957–August 2002) ERA-40 wave reanalysis data from the European Centre for Medium-Range Weather Forecasts(ECMWF) to analyze the impact of the South Indian Ocean westerlies on the propagation of swell acreage. The following results were obtained: 1) The South Indian Ocean swell mainly propagates from southwest to northeast. The swell also spreads to the Arabian Sea upon reaching low-latitude waters. The 2.0-meter contour of the swell can reach northward to Sri Lankan waters. 2) The size of the IOSDEI is determined by the SIWI strength. The IOSDEI requires approximately 2–3.5 days to fully respond to the SIWI. The correlations between SIWI and IOSDEI show obvious seasonal differences, with the highest correlations found in December–January–February(DJF) and the lowest correlations observed in June–July–August(JJA). 3) The SIWI and IOSDEI have a common period of approximately 1 week in JJA and DJF. The SIWI leads by approximately 2–3 days in this common period.  相似文献   

Snow Depth Inversion Using the Localized HUT Model Based on FY-3B MWRI Data in the Farmland of Heilongjiang Province,China     

Lili Wu  Xiaofeng Li  Kai Zhao  Xingming Zheng 《Journal of the Indian Society of Remote Sensing》2017,45(1):89-100

Snow depth parameter inversion in the farmland using passive microwave remote sensing is of great significance to the agricultural production in Northeast China. Firstly, the Helsinki University of Technology (HUT) snow emission model was validated in the farmland based on microwave radiation imager (MWRI) onboard FengYun-3B satellite (FY-3B). The results showed that there was a big difference between the brightness temperature of HUT model simulation and MWRI for 18.7 GHz horizontal polarization (18.7 H) and 36.5 GHz horizontal polarization (36.5 H). To improve HUT model, the empirical parameter in the model was localized. Then the localized HUT (LHUT) model was built, where the extinction coefficient was calculated by the new extinction coefficient formula. Next, LHUT model was validated based on MWRI data and compared with HUT model. The results showed that LHUT underestimates slightly the brightness temperature with 0.91 and 4.19 K for 18.7 and 36.5 H respectively, and LHUT is superior to HUT model. Finally, the genetic algorithm (GA) was used to invert snow depth based on LHUT. The results showed that snow depth was underestimated with 6.79 cm based on LHUT. The inverted snow depth based on LHUT model is in better agreement with the measured snow depth.  相似文献   

Description of Salient Features Combined with Local Self-Similarity for SAR Image Registration     

Lijuan Yang  Zheng Tian  Wei Zhao  Weidong Yan  Jinhuan Wen 《Journal of the Indian Society of Remote Sensing》2017,45(1):131-138

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自适应窗口的SAR立体影像匹配方法     

王亚超  杨书成  赵争  卢丽君 《测绘科学》2017,42(2)

针对SAR立体影像间几何畸变对影像匹配的影响,该文提出一种自适应窗口的SAR立体影像匹配方法。首先引入外部粗分辨率DEM,根据影像参数和DEM高程精度约束匹配搜索范围。然后采用归一化互相关和测度进行辅影像匹配窗口自适应扩展匹配,以保证主辅影像匹配窗口内的灰度信息一致;归一化互相关和值最大时的辅影像匹配窗口为最佳匹配窗口,最佳匹配窗口的中心点为获取的匹配点。最后利用双向一致性约束剔除误匹配点。试验结果表明,本文方法在山地区域能有效地增加正确匹配点数量,提高匹配正确率。  相似文献   

小比例尺道路网眼约束下的多尺度道路网自动匹配     

裴洪星  翟仁健  武芳  李靖涵  巩现勇  吴铮 《测绘学报》2017,46(6):760-769

针对道路网多尺度匹配的问题,提出了一种在小比例尺数据道路网眼约束下的多尺度道路匹配方法。首先,构建两幅不同比例尺数据的道路网眼;其次,在小比例尺道路网眼的约束下,提取出大比例尺道路中由若干道路网眼构成的复合网眼,并完成与小比例尺道路网眼具有多对一和一对一关系的网眼匹配;然后,实现不同比例尺道路网眼的多对多匹配;最后,由复合网眼与小比例尺道路网眼的匹配关系转化为多比例尺道路网眼边界道路之间的匹配和内部道路之间的匹配,完成整个道路网的匹配。试验结果证明,本方法能较好地实现多尺度道路网的匹配。  相似文献