无人机倾斜摄影及自动三维建模技术在地质灾害应急测绘中的应用——以三明市妙元山为例

利用无人机获取多视角的倾斜影像,结合自动三维建模技术,模拟地质灾害受灾情况,可以对受灾程度进行定性、定量分析管理,能够快速准确地评估受灾情况,为救灾工作提供决策支持。     

无人机技术在日常地籍测绘中的应用

随着经济的发展,不动产权变更的工作也日益增多。因地区发展差异,赤峰地区在2006年以前地籍数据并未纳入国家坐标系,为此,加重了日常地籍测绘工作。城区的观测条件,如高层楼房与电力设施等不利因素给测量带来巨大不便,而无人机测绘技术在实际应用中体现了巨大的优势与可能性,其精度也保证了测绘质量需求。     

浅谈测绘监理在第三次国土调查中的运用 ——以益阳市第三次国土调查监理为例

从1988年建设部颁布《关于开展建设监理工作的通知》算起,在我国工程建设领域推行工程监理制度已有三十多年历史.工程监理在工程建设过程中发挥了重要作用,我国目前在工程领域建立了完善的监理法规及标准体系,形成了较为完整的工程监理机制.但在测绘领域,全面推行测绘监理仍尚需时日,有待健全.湖南省各市州第三次国土调查项目引入了监...     

稳定风浪场谱特征量间的关系

风浪宏观特征量是描述风浪场特征的重要物理量。作者基于风浪有停留在混乱运动状态的趋势的性质对风浪场特征量间的关系进行了研究。主频波频率附近的波动自风摄取能量,风浪吸收的能量通过非线性相互作用在谱中重新分配。谱中能量的重新分配产生多尺度波动,这导致风浪波面的混乱运动(风浪处于混乱运动状态)。在稳定状态,风浪运动最为混乱。当风浪状态偏离最混乱运动状态,谱中非线性相互作用引起的能量重新分配将使风浪回到该状态。基于线性海浪理论导出风浪场特征量间的关系。导出的关系与观测结果进行了对比,发现理论结果与观测结果很好地符合。风浪场宏观特征量间存在固有关系。尽管目前风浪场特征量关系的观测结果存在差异,但本文中证明,所导出的理论关系与实验结果很好地符合。     

Ekman drift and vortical structures

In this article, the authors study the influence of a constant wind on the displacement of a vortex. The well known Ekman current develops in the surface layer and is responsible for a transport perpendicular to the wind: the Ekman drift.An additional process is, however, evidenced, whose importance is as strong as the Ekman drift. There indeed exists a curl of the wind-driven acceleration along isopycnic surfaces when they are spatially variable (they enter and leave the depth where the wind stress acts), which generates potential vorticity anomalies. This diabatic effect is shown to generate potential vorticity anomalies which acts on the propagation of vortical waves and non linear vortices.It is shown that this effect drastically reduces the effect of the Ekman drift for linear waves and surface intensified vortices, while extending its effect to subsurface vortices. It also generates along wind propagation, whose sign depends on the vortex characteristics.     

Coupling winds to ocean surface currents over the global ocean

A Wind stress–Current Coupled System (WCCS) consisting of the HYbrid Coordinate Ocean Model (HYCOM) and an improved wind stress algorithm based on Donelan et al. [Donelan, W.M., Drennan, Katsaros, K.B., 1997. The air–sea momentum flux in mixed wind sea and swell conditions. J. Phys. Oceanogr. 27, 2087–2099] is developed by using the Earth System Modeling Framework (ESMF). The WCCS is applied to the global ocean to study the interactions between the wind stress and the ocean surface currents. In this study, the ocean surface current velocity is taken into consideration in the wind stress calculation and air–sea heat flux calculation. The wind stress that contains the effect of ocean surface current velocity will be used to force the HYCOM. The results indicate that the ocean surface velocity exerts an important influence on the wind stress, which, in turn, significantly affects the global ocean surface currents, air–sea heat fluxes, and the thickness of ocean surface boundary layer. Comparison with the TOGA TAO buoy data, the sea surface temperature from the wind–current coupled simulation showed noticeable improvement over the stand-alone HYCOM simulation.     

Mapping of aggregated floodplain plant communities using image fusion of CASI and LiDAR data

Combined optical and laser altimeter data offer the potential to map and monitor plant communities based on their spectral and structural characteristics. A problem unresolved is, however, that narrowly defined plant communities, i.e. plant communities at a low hierarchical level of classification in the Braun-Blanquet system, often cannot be linked directly to remote sensing data for vegetation mapping. We studied whether and how a floristic dataset can be aggregated into a few major discrete, mappable classes without substantial loss of ecological meaning. Multi-source airborne data (CASI and LiDAR) and floristic field data were collected for a floodplain along the river Waal in the Netherlands. Mapping results based on floristic similarity alone did not achieve highest levels of accuracy. Ordination of floristic data showed that terrain elevation and soil moisture were the main underlying environmental drivers shaping the floodplain vegetation, but grouping of plant communities based on their position in the ordination space is not always obvious. Combined ordination-based grouping with floristic similarity clustering led to syntaxonomically relevant aggregated plant assemblages and yielded highest mapping accuracies.     

RTK配合全站仪在数字化测图中的应用

本文主要叙述了RTK配合全站仪进行数字化测图的可行性,介绍了RTK的系统组成、工作原理,并对RTK配合全站仪联合测图的作业流程进行了一系列论述;指出了RTK与全站仪联合进行数字化测图是一种高速度、高效率的新方法.     

Vision-based tracking with projective mapping for parameter identification of remotely operated vehicles

Parameter identification of a remotely operated vehicle (ROV) is often based on the dynamic responses collected by its onboard sensors. However, for commercial ROVs, the required data for identification may not be available due to the absence of suitable sensors or limitations in accessing onboard sensor data. Therefore, this study proposes a vision-based tracking system to measure the dynamic response of an ROV. The tracking system is independent of the ROV, and is able to localize an ROV to a high degree of precision by means of projective mapping. The validity of the proposed tracking system is demonstrated through identification of a commercial ROV. A simplified nonlinear ROV dynamic model with six degrees of freedom (DOF) is used for identification. Uncoupled motions, including surge, sway, and yaw, are obtained from the ROV dynamic model, and the corresponding experiments are carried out for each DOF. Hydrodynamic parameters are then estimated with numerical optimizations by comparing the measured ROV responses with the output of the mathematical model. The experimental results show that the vision-based tracking system can accurately measure the transient and steady-state responses of an ROV. Additionally, the simulations of the ROV dynamic model, with the optimal parameter estimates, give results in agreement with the measured data.     

Use of SPOT 5 and IKONOS imagery for mapping biocenoses in a Tunisian Coastal Lagoon (Mediterranean Sea)

Mapping marine biocenoses is an efficient method for providing useful data for the management and conservation of Mediterranean lagoons. Fused images from two satellites, SPOT 5 and IKONOS, were tested as management tools for identifying specific ecosystems in the El Bibane lagoon, situated in southern Tunisia near the Libyan border. The objectives of this study were to provide a precise map of the entire El Bibane lagoon using fused images from SPOT 5 and to compare fused images from SPOT 5 and IKONOS over a test-area. After applying a supervised classification, pixels are automatically classified in four classes: low seagrass cover, high seagrass cover, superficial mobile sediments and deep mobile sediments. The maps of the lagoon revealed and confirmed an extremely wide distribution of seagrass meadows within the lagoon (essentially Cymodocea nodosa; 19 546 ha) and a large area of mobile sediments more or less parallel to the shore (3 697 ha). A direct comparison of overall accuracy between SPOT 5 over the entire area, SPOT 5 over the test-area and IKONOS over the test-area revealed that these tools provided accurate mapping of the lagoon environment (83.25%, 85.91% and 73.41% accuracy, respectively). The SPOT 5 images provided greater overall accuracy than the IKONOS image, but did not take into account the heterogeneous spatial structure of the seagrasses and sediments present in the lagoon environment. Although IKONOS imagery provided lower overall accuracy than SPOT 5, it proved a very useful tool for the mapping of heterogeneous structures as it enabled the patchiness of formations to be better taken into account. The use of SPOT 5 and IKONOS fused images appears to be very promising for completing the mapping of lagoons in other regions and countries of the Mediterranean Sea.