模糊神经网络在GPS高程转换中的应用   总被引：1，自引：1，他引：0  

方毅  雒卫民 《地理空间信息》2009,7(4):108-110

介绍了T-S模糊神经网络的基本原理以及如何确定GPS高程转换的模糊神经网络模型，并采用该模型对实测数据进行了计算分析。结果表明，模糊神经网络能够对小区域GPS高程做出比较准确定的拟合，从而能够为GPS高程转换提供一种较好的方法，能够满足实际工程需要。  相似文献   

GPS高程拟合技术在兵团新建58团1/1万航测外业中的应用     

高永甲  孙加强 《北京测绘》2009,(1)

介绍了用GPS定位技术在兵团农三师新建58团1/1万航测地形图测绘外业像控点高程拟合精度,经实地用水准仪采用几何测量检查GPS拟合点的高程,证明GPS高程拟合精度与已如点的数量、精度和位置有关,其中已知点的分布对其影响最大,对于一定面积的小比例尺的航外像控测量,当已知点均匀分布于整个测区时,GPS拟合的高程可满足像控点精度要求。  相似文献   

2D Wave setup behind submerged breakwaters     

M. Calabrese  D. Vicinanza  M. Buccino   《Ocean Engineering》2008,35(10):1015-1028

In addition to reducing the incoming wave energy, submerged breakwaters also cause a setup of the sea level in the protected area, which is relevant to the whole shadow zone circulation, including alongshore currents and seaward flows through the gaps. This study examines such a leading hydraulic parameter under the simplified hypothesis of 2D motion and presents a prediction model that has been validated by a wide ensemble of experimental data. Starting from an approach originally proposed by Dalrymple and Dean [(1971). Piling-up behind low and submerged permeable breakwaters. Discussion note on Diskin et al. (1970). Journal of Waterways and Harbors Division WW2, 423–427], the model splits the rise of the mean water level into two contributions: one is due to the momentum flux release forced by wave breaking on the structure, and the other is associated with the mass transport process. For the first time, the case of random wave trains has been explicitly considered.  相似文献   

Radar cross section analysis of marine targets using a combining method of physical optics/geometric optics and a Monte-Carlo simulation     

Kookhyun Kim  Jin-Hyeong Kim 《Ocean Engineering》2009,36(11):821-830

In this paper, the radar cross section of flat plates on ocean surfaces is statistically investigated. A combining method of physical optics and geometric optics is applied to establish an effective backscattering analysis procedure. This method is a high-frequency analysis method originally derived from a simplified Stratton-Chu integral equation, assuming that the radar is far away from the target so that Kirchhoff approximation is valid. A Monte-Carlo simulation method is adopted to statistically analyze the effects of undulated ocean surfaces. The ocean surfaces are randomly generated by Pierson-Moskowitz ocean wave spectrum and a directional distribution function. Numerical investigations are carried out for flat plates, with the same height and width but with different inclined angles, on ocean surfaces of various significant wave heights.  相似文献   

Onshore sandbar migration at Tairua Beach (New Zealand): Numerical simulations and field measurements   总被引：1，自引：0，他引：1  

B. van Maanen  P.J. de Ruiter  Giovanni Coco  K.R. Bryan  B.G. Ruessink 《Marine Geology》2008,253(3-4):99-106

We observed the onshore migration (3.5 m/day) of a nearshore sandbar at Tairua Beach, New Zealand during 4 days of low-energy wave conditions. The morphological observations, together with concurrent measurements of waves and suspended sediment concentrations, were used to test a coupled, wave-averaged, cross-shore model. Because of the coarse bed material and the relatively low-energy conditions, the contribution of the suspended transport to the total transport was predicted and observed to be negligible. The model predicted the bar to move onshore because of the feedback between near-bed wave skewness, bedload, and the sandbar under weakly to non-breaking conditions at high tide. The predicted bathymetric evolution contrasts, however, with the observations that the bar migrated onshore predominantly at low tide. Also, the model flattened the bar, while in the observations the sandbar retained its steep landward-facing flank. A comparison between available observations and numerical simulations suggests that onshore propagating surf zone bores in very shallow water (< 0.25 m) may have been responsible for most of the observed bar behaviour. These processes are missing from the applied model and, given that the observed conditions can be considered typical of very shallow sandbars, highlight a priority for further field study and model development. The possibility that the excess water transported by the bores across the bar was channelled alongshore to near-by rip-channels further implies that traditional cross-shore measures to judge the applicability of a cross-shore morphodynamic model may be misleading.  相似文献   

西沙湾工程波浪推算及波浪场数值模拟          下载免费PDF全文

林毅辉  郑艺妃  潘伟然  肖征  姬厚德 《应用海洋学学报》2020,39(1):80-86

本研究根据崇武水文站1976—2007年共31 a的波浪观测资料,使用皮尔逊Ⅲ型频率曲线进行拟合分析,推算出崇武在不同重现期条件下的特征波浪要素,再将其作为外海波浪要素输入,通过基于椭圆型缓坡方程的CGWAVE近岸波浪数值模型,模拟西沙湾的重现期波浪场,得到其设计波浪要素,得到较为合理的计算结果。西沙湾的海底地形强烈地影响近岸波浪,导致了波高和波向的不均匀分布特征,岛屿和礁石都是天然屏障,东侧水域受龟屿及闽台码头的掩护,波浪反射、绕射明显,对避风坞起到了有效的保护作用。此外,对于不同地质的边界,反射系数不同使得近岸波高分布有较大差异。  相似文献   

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李玉江  陈连旺  李红  叶际阳 《大地测量与地球动力学》2009,29(4):26-29

???????????????????????????鹹???????????????????????о?????????????????????GPS?????????????????????????,?????????????????????????????????????????????????????6??????????????????????????????????????????????????????????????????????????????н???????, ??????????????3????????Σ??????  相似文献   

Wave Height Estimation from SAR Imagery     

杨劲松黄韦艮  周成虎肖清梅 《中国海洋湖沼学报》2004,22(2):157-161

This paper presents a method developed for estimating wave height from synthetic aperture radar (SAR) imagery without prior assumption of noise distribution. It is based on two-dimenslonal ocean wave spectra retrieved from fully calibrated SAR images. Wen‘s spectrum was used as first-guess wave spectrum in the retrieval process. Comparison of the estimated wave height obtained by this method from two ERS-1 SAR subimages dated 23 July 1994 with in-situ measurements showed that the method works well.  相似文献   

全站仪三角高程测量的精度分析和计算自动化     

曾庆伟 《北京测绘》2009,(4):43-45

全站仪三角高程测量具有效率高，实施灵活等优点，经研究并通过实践验证，在对观测结果进行相关改正的条件下，全站仪三角高程测量完全能达到三、四等水准测量的精度要求，同时可借助Excel所具备的强大数据处理能力，使观测数据的处理更为方便快捷。  相似文献   

Predicting tsunami arrivals: Estimates and policy implications     

Dao Hua Zhang  Tsz Leung Yip  Chiu-On Ng 《Marine Policy》2009

Tsunami is one of a few kinds of natural disasters that leave people some time for escape. This escape time, which is essentially the time for the giant wave to propagate from the epicentre to a coast, has to be estimated without delay upon the occurrence of the incident. With the advancement of water wave theories, much work has been done to model the propagation of tsunamis from deep oceans to shallow water. The authors argue that while much emphasis has been put on the expansion of the high-tech early warning system and the development of complicated tsunami models, a simple-to-use yet accurate predictive model is still wanting. This paper presents a handy linear wave model, which is capable of estimating the arrival time of a tsunami with very good accuracy, as has been verified by comparison with past incidents. With the availability of such a simple model, even local communities without access to a high-tech warning system can readily estimate the time left for emergency evacuation.  相似文献