It is necessary to deploy high-resolution topographic surveys in a typical small target in deep-sea areas (e.g.hydrothermal seep,ridge area) to support the future further studies,after the full-covered topography data acquisition of the large study area using a shipborne mutli-beam system.Here,we select PACMANUS hydrothermal area as target area in the Manus Basin and deploy a near-bottom full-covered survey to obtain topography data basing on "FAXIAN" ROV.Results show that Long Baseline provide a reliable high-precision positioning relying on the ship dynamic positioning system and a differential GPS.The resolution of seabed topography which is near-bottom measured by ROV is tens of times better than that obtained by an onboard multi-beam system.High-resolution terrain clearly shows the detailed characters of the terrain in the PACMANUS hydrothermal field,and some cones are corresponding to the locations of the discovered hydrothermal points and volcanic area.Further analysis show that hydrothermal points mainly developed on the steep slopes whose gradients exceed 30°,and the causes are still unknown and need a further study.It is a reliable mean for obtaining high-resolution topography data by deploying near-bottom measure ments using ROV,which will promote the development of deep-sea scientific research.%针对重点的特殊深海研究区(如热液冷泉、洋中脊区域),在船载多波束数据获得研究区大面积地形资料的基础上,有必要选取典型深海小靶区进行高分辨率地形测量为进一步深入研究提供保障.根据船载多波束实测数据选取PACMANUS热液区作为靶区,基于长基线定位,利用“发现”ROV搭载多波束系统进行近海底全覆盖地形测量.结果表明,依托于船动力定位系统及差分GPS,长基线为ROV提供了可靠的高精度定位,使得近海底测量的地形数据分辨率数倍优于船载多波束测得的地形数据的分辨率.高分辨率地形清晰的显示了PACMANUS热液区锥形丘体等特殊微地形,与已发现的热液点和火山区有很好的对应.进一步分析发现,该区域活动的热液区主要发育于坡度大于30°斜坡上的地形突变区,其成因仍需深入研究.利用ROV搭载多波束近底测量是获取深海小靶区高分辨率地形的可靠途径和方法,有利于提高深海海底研究的针对性,将促进我国深海科学研究的发展.
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