Improving the Position Accuracy and Computational Efficiency of UAV Terrain Aided Navigation Using a Two-Stage Hybrid Fuzzy Particle Filtering Method

Terrain Aided Navigation(TAN)technology has become increasingly important due to its effectiveness in environments where Global Positioning System(GPS)is unavailable.In recent years,TAN systems have been extensively researched for both aerial and underwater navigation applications.However,many TAN systems that rely on recursive Unmanned Aerial Vehicle(UAV)position estimation methods,such as Extended Kalman Filters(EKF),often face challenges with divergence and instability,particularly in highly non-linear systems.To address these issues,this paper proposes and investigates a hybrid two-stage TAN positioning system for UAVs that utilizes Particle Filter.To enhance the system’s robustness against uncertainties caused by noise and to estimate additional system states,a Fuzzy Particle Filter(FPF)is employed in the first stage.This approach introduces a novel terrain composite feature that enables a fuzzy expert system to analyze terrain non-linearities and dynamically adjust the number of particles in real-time.This design allows the UAV to be efficiently localized in GPS-denied environments while also reducing the computational complexity of the particle filter in real-time applications.In the second stage,an Error State Kalman Filter(ESKF)is implemented to estimate the UAV’s altitude.The ESKF is chosen over the conventional EKF method because it is more suitable for non-linear systems.Simulation results demonstrate that the proposed fuzzy-based terrain composite method achieves high positional accuracy while reducing computational time and memory usage.

Displacement field reconstruction in landslide physical modeling by using a terrain laser scanner e Part 1:Methodology,error analysis and validation

Laser scanning technology has been widely used in landslide aspects.However,the existing deformation analysis based on terrain laser scanners can only provide limited information,which is insufficient for understanding landslide kinematics and failure mechanisms.To overcome this limitation,this paper proposes an automated method for processing point clouds collected in landslide physical modeling.This method allows the acquisition of quantitative three-dimensional(3D)deformation field information.The results show the organized and spatially related point cloud segmentation in terms of spherical targets.The segmented point clouds can be fitted to determine the locations of all preset targets and their corresponding location changes.The proposed method has been validated based on theoretical analysis and numerical and physical tests,which indicates that it can batch-process massive data sets with high computational efficiency and good noise resistance.Compared to existing methods,this method shows a significant potential for understanding landslide kinematics and failure mechanisms and advancing the application of 3D laser scanning in geotechnical modeling.

Relationships between Terrain Features and Forecasting Errors of Surface Wind Speeds in a Mesoscale Numerical Weather Prediction Model

Numerical weather prediction(NWP)models have always presented large forecasting errors of surface wind speeds over regions with complex terrain.In this study,surface wind forecasts from an operational NWP model,the SMS-WARR(Shanghai Meteorological Service-WRF ADAS Rapid Refresh System),are analyzed to quantitatively reveal the relationships between the forecasted surface wind speed errors and terrain features,with the intent of providing clues to better apply the NWP model to complex terrain regions.The terrain features are described by three parameters:the standard deviation of the model grid-scale orography,terrain height error of the model,and slope angle.The results show that the forecast bias has a unimodal distribution with a change in the standard deviation of orography.The minimum ME(the mean value of bias)is 1.2 m s^(-1) when the standard deviation is between 60 and 70 m.A positive correlation exists between bias and terrain height error,with the ME increasing by 10%−30%for every 200 m increase in terrain height error.The ME decreases by 65.6%when slope angle increases from(0.5°−1.5°)to larger than 3.5°for uphill winds but increases by 35.4%when the absolute value of slope angle increases from(0.5°−1.5°)to(2.5°−3.5°)for downhill winds.Several sensitivity experiments are carried out with a model output statistical(MOS)calibration model for surface wind speeds and ME(RMSE)has been reduced by 90%(30%)by introducing terrain parameters,demonstrating the value of this study.

HOG-VGG:VGG Network with HOG Feature Fusion for High-Precision PolSAR Terrain Classification

This article proposes a VGG network with histogram of oriented gradient(HOG) feature fusion(HOG-VGG) for polarization synthetic aperture radar(PolSAR) image terrain classification.VGG-Net has a strong ability of deep feature extraction,which can fully extract the global deep features of different terrains in PolSAR images,so it is widely used in PolSAR terrain classification.However,VGG-Net ignores the local edge & shape features,resulting in incomplete feature representation of the PolSAR terrains,as a consequence,the terrain classification accuracy is not promising.In fact,edge and shape features play an important role in PolSAR terrain classification.To solve this problem,a new VGG network with HOG feature fusion was specifically proposed for high-precision PolSAR terrain classification.HOG-VGG extracts both the global deep semantic features and the local edge & shape features of the PolSAR terrains,so the terrain feature representation completeness is greatly elevated.Moreover,HOG-VGG optimally fuses the global deep features and the local edge & shape features to achieve the best classification results.The superiority of HOG-VGG is verified on the Flevoland,San Francisco and Oberpfaffenhofen datasets.Experiments show that the proposed HOG-VGG achieves much better PolSAR terrain classification performance,with overall accuracies of 97.54%,94.63%,and 96.07%,respectively.

四川复杂地形下雷暴大风客观预报方法研究

地形复杂的四川地区,虽然雷暴大风发生频次较低,但造成的影响重大,现有的客观预报产品较少且时间分辨率低,为进一步提升四川复杂地形下雷暴大风预报准确率,综合考虑地形因子、模式物理量因子和时间因子,根据海拔高度将四川分为高海拔区和低海拔区,利用2018—2021年数据基于随机森林、自适应提升法、极端随机树三种机器学习方法分区构建雷暴大风预报模型,对2022年进行预报,获得逐3 h雷暴大风潜势预报,再利用气候背景将3 h预报时间降尺度到1 h,形成0~12 h逐小时雷暴大风预报,并检验预报效果。结果表明,逐3 h雷暴大风预报以自适应提升法效果最优,长时间检验和个例检验都表明,基于自适应提升法获得的0~12 h逐小时雷暴大风预报产品优于中央气象台产品,TS评分由0.0104提升至0.0595,空报率由0.988下降至0.808,业务应用价值较高。

秦岭山脉南北麓暴雨触发条件对比分析

采用实况气象观测资料、FY-2G卫星云图资料、多普勒雷达资料和ERA50.25°×0.25°逐小时再分析资料,对2021年8月21-22日同时发生在秦岭南北麓的强等级暴雨过程进行对比分析,探讨秦岭南北麓暴雨触发条件的影响机制。结果表明:秦岭北麓流场上,西风带系统在秦岭特殊地形作用下,对流层低层形成中尺度气旋性环流,通过热力作用触发暴雨,对流性降水持续时间短,强度小;湿斜压性增强是秦岭北麓暴雨开始的一个信号,当湿斜压性减弱以及中层比湿减小时,降水结束。对秦岭南麓而言,地形作用下对流层低层流场形成中尺度辐合线触发暴雨;降水释放的凝结潜热加热低层大气,与中低层入侵的冷空气共同构建对流不稳定结构,上升运动增强,降水增强和持续;对流云团在高温高湿的环境下迅速组织化合并发展,形成中尺度对流复合体(MCC),对流强度大,对流层结深厚,小时雨强大;中低层冷空气的入侵和扩散到地面的时间分别与秦岭南麓强降水的开始和结束时间对应。

基于GIM技术的输变电工程三维基础设计场景构建

为提升输变电工程三维基础设计场景构建效率,提出基于GIM技术的输变电工程三维基础设计场景构建。通过无人机扫描目标区域的环境信息,运用Grid建模方法生成三维地形图。以电网信息模型技术为核心,设计三维参数化建模方法,通过调整参数值,快速编辑输变电工程本体结构。经过坐标系转换,将输变电本体结构放置于三维地形场景内,合成输变电工程三维基础设计场景。再通过LOD细节模型,实现可视化三维场景的高效渲染。实验结果显示:应用所提方法构建三维场景模型耗费时间为21.5 min,较其他方法构建耗时最高降低了70.22%,效率得到了很大程度的提高,具有较为优越的应用性能。

Simulation Analysis on A Rainstorm in Guizhou and Numerical Test about the Terrain Impact

A rainstorm caused by mesoscale convective system (MCS) in Guizhou Province in June 25-26 in 2005 was simulated with the MM5 model. Based on the good simulated results of the MCS developing and the clouds physics process, and by means of reducing the height of Yunnan-Guizhou Plateau and cutting off the middle-east of the Yunnan-Guizhou Plateau on the simulated tests, the question as how the ladder terrain on the west of Yunnan-Guizhou Plateau impact on the rainstorm of Guizhou was studied. The analysis results showed that the second ladder terrain of Yunnan-Guizhou Plateau only affected the development of convective clouds on its backward position,and hardly affected the rain on its upward. The whole terrain of the Yunnan-Guizhou Plateau had a distinct impact not only on the windward slope rainfall of the west of the plateau, but also on the rainfall distribution, intensity and continuing time of the convective clouds on the middle-east of the plateau.

Application of unscented Kalman filter to novel terrain passive integrated navigation system

To improve the navigation accuracy of an autonomous underwater vehicle （AUV）, a novel terrain passive integrated navigation system （TPINS） is presented. According to the characteristics of the underwater environment and AUV navigation requirements of low cost and high accuracy, a novel TPINS is designed with a configuration of the strapdown inertial navigation system （SINS）, the terrain reference navigation system （TRNS）, the Doppler velocity sonar （DVS）, the magnetic compass and the navigation computer utilizing the unscented Kalman filter （UKF） to fuse the navigation information from various navigation sensors. Linear filter equations for the extended Kalman filter （EKF）, nonlinear filter equations for the UKF and measurement equations of navigation sensors are addressed. It is indicated from the comparable simulation experiments of the EKF and the UKF that AUV navigation precision is improved substantially with the proposed sensors and the UKF when compared to the EKF. The TPINS designed with the proposed sensors and the UKF is effective in reducing AUV navigation position errors and improving the stability and precision of the AUV underwater integrated navigation.

RANDOM TERRAIN MODEL

In order to slove a realistic test problem of TF/TA algorithm, it is necessary to make a discrete terrain model. The model has adjustable roughness parameters so as to test the optimization procedure for different types of terrain. In this paper, an algorithm to generate random terrain data is given.

复杂地形区域一次雹暴过程的观测及模拟研究

为提高中国西南复杂地形区域雹暴预报水平,对该区域内一次典型雹暴过程中的地形作用、微物理过程及成雹机制进行系统分析,并采用全弹性三维对流云模式进行数值模拟。结果表明:(1)雹暴过程为冷空气侵入型,地形对低层暖湿气流的阻拦导致水汽的积累,同时高原槽引导的冷空气触发雹暴。(2)近地面层或500~300 hPa高度层的>8×10^(-5)/s的涡度中心、750 hPa高度存在散度<-8×10^(-5)/s的辐合中心且在500 hPa或以上层次转为辐散、近地面层水汽通量散度<-12×10^(-8)g/(s·cm^(2)·hPa)、假相当位温梯度>4 K/km、0~6 km垂直风切变>15 m/s这几个阈值可以为西南复杂地形区域的雹暴过程提供预警。(3)32.03 m/s的强垂直风切变和旋转速度达19.85 m/s、厚度超3 km的强中气旋是降雹单体的主要维持机制。(4)雹胚主要由雪晶撞冻过冷雨滴产生,低密度霰在沉降过程中凇附云水和过冷雨滴增长成雹是主要的成雹机制。对贵州地区雹暴过程的预报具有一定指导作用。

第五代PSU/NCAR中尺度模式系统(MM5)介绍I:地形及地表分类参数处理(TERRAIN模块)

利用TERRAIN模块的主要功能、结构和原理对模块的安装和操作使用给予了说明。同时 ,为了加深读者对该模块的认识 ,对不同分辨率的地形、地表分类参数的处理进行比较 ,分析结果表明 ,高分辨率地形及地表分类资料的选取能更真实地反映出下垫面的实际特征 ,是今后进行中尺度天气预报和数值模拟的基础之一。

基于Terrain model的三角化运算法则

针对目前出现的大量的物体表面扫描数据的分割与插值方法,本文提出了一个新的适合Terrain model及其相近的三角化运算法则,并给出了部分运算程序代码。该运算法则经检验与运用,具有很好的实用性。

Singularity-free expression of magnetic field of cuboid under undulating terrain

Most of the current computing methods used to determine the magnetic field of a uniformly magnetized cuboid assume that the observation point is located in the upper half space without a source. However, such methods may generate analytical singularities for conditions of undulating terrain. Based on basic geomagnetic field theories, in this study an improved magnetic field expression is derived using an integration method of variable substitution, and all singularity problems for the entire space without a source are discussed and solved. This integration process is simpler than that of previous methods, and final integral results with a more uniform form. AT at all points in the source-flee space can be calculated without requiring coordinate transformation; thus forward modeling is also simplified. Corresponding model tests indicate that the new magnetic field expression is more correct because there is no analytical singularity and can be used with undulating terrain.

近距离大埋深金属管线探测方法及应用

随着工程建设的发展,近距离大埋深地下管线的探测成为当前工程领域的难点。针对近距离大埋深金属管线探测,本文研究了水平电磁剖面法,首次提出了间接充电法信号加载方法,并采用了带地形改正的磁感应强度反演方法。文章结合一个多条近距离敷设埋深大于12m的地下管线探测实例,详细阐述了探测过程中的关键技术及解决方案。探测结果经人工开挖验证,完全符合实际,精度满足要求,可为类似工程提供参考和借鉴。

西藏雅砻河流域生态系统服务价值地形梯度分异及驱动因素

[目的]分析雅砻河流域生态系统服务价值的变化,为流域生态文明建设提供科学依据。[方法]基于高精度土地利用数据,运用地形梯度分级、标准差椭圆和地理探测器,探究了近20年流域生态系统服务价值(Ecosystem service value,ESV)的时空演变和地形梯度分异特征。[结果](1)草地是流域主要的土地利用类型,占比达92.45%。研究期内林地、灌木和草地面积有所减少,其他类型有所增加;(2)流域ESV在研究期间增长了0.13%(0.16亿元),ESV在空间上呈现出东南部高西北部低的特征。随着海拔、坡度和地形起伏度的抬升,ESV呈先增后降的分布规律,坡向梯度呈阴坡高于阳坡的特征。(3)流域ESV的标准差椭圆和重心在研究期内逐渐向西南方向移动,并趋于聚集。ESV的空间分异主要受自然和经济因子的影响,其中年均地温是主导因子(q=0.24),任意因子交互均增强了其分异性。[结论]依据雅砻河流域ESV的时空和地形分布特征,采取因地制宜的生态保护措施,促进流域生态环境的可持续发展。

唐山市植被覆盖度时空演变及地形因子的响应

植被覆盖度在生态环境质量评价、地表过程监测和生态保护决策等方面发挥着重要作用。研究基于GEE平台,采用像元二分法获取唐山市不同时段的植被覆盖度。通过Sen趋势分析和MK检验探讨植被覆盖度的时空演变情况。利用GIS叠加分析研究植被覆盖度与地形因子的关系。结果表明:(1)唐山市植被覆盖度稳定,城市建设区域和南部沿海地区较低,中部和北部低山区较高,中等级及以上占比超过65%。(2)在2001~2021年间,唐山市的植被覆盖度轻微改善,改善面积达到了39.041%。(3)植被覆盖度与高程和坡度显著相关,特别在高程200米以上和坡度15°~32°范围内,中高等级和高等级植被覆盖度较高。探究植被覆盖度演变对该地区的生态环境改善具有重要意义。

河套地区边界层辐合线形成及其对流触发作用

利用加密小球探空、野外地面加密观测站、ERA5再分析资料、临河新一代天气雷达等资料,对2022年7—8月内蒙古黄河河套地区由河套灌区与库布奇沙漠地表差异形成的边界层辐合线(BLCL)及其在对流触发中的作用进行了详细分析。结果表明:河套BLCL是由地表差异、边界层大气环流、复杂地形共同影响所形成,主要发生在河套灌区东南部的库布奇沙漠地区,长度在100~200 km,为浅薄系统,垂直厚度约为1000~1100 m。BLCL日变化明显,在12:00—17:00为高发时段,占80%。7—8月BLCL形成概率高达60%,且有39%的BLCL会触发对流。BLCL形成的预报指标为:河套灌区杭锦后旗较库布奇沙漠哈百来更的2 m气温低2.5℃以上、露点温度高6℃以上、相对湿度高20%以上;河套套内库布奇沙漠和毛乌素沙地区域为持续强劲的偏南风,地面10 m风速大值中心大于4 m·s-1;海平面气压场西低东高,黄河“几”字弯为等压线密集带,气压梯度达3~4 hPa·100 km-1。BLCL的形成对对流触发具有重要意义,表现为对流触发、加强、组织等作用,在不同的环境条件和天气系统叠加配置下会触发局地对流、有组织强对流,导致河套地区暴雨等天气。河套BLCL在这一特定地区的生成和对流触发作用,与河套地区降水自西向东急剧增多的分布特征关系密切。

Field Relationships,Geochemistry,Zircon Ages and Evolution of a Late Archaean to Palaeoproterozoic Lower Crustal Section in the Hengshan Terrain of Northern China

The Hengshan complex forms part of the central zone of the North China Craton and consists predominantly of ductilely-deformed late Archaean to Palaeoproterozoic high-grade, partly migmatitic, granitoid orthogneisses, intruded by mafic dykes of gabbroic composition. Many highly strained rocks were previously misinterpreted as supracrustal sequences and represent mylonitized granitoids and sheared dykes. Our single zircon dating documents magmatic granitoid emplacement ages between 2.52 Ga and 2.48 Ga, with rare occurrences of 2.7 Ga gneisses, possibly reflecting an older basement. A few granitic gneisses have emplacement ages between 2.35 and 2.1 Ga and show the same structural features as the older rocks, indicating that the main deformation occurred after -2.1 Ga. Intrusion of gabbroic dykes occurred at -1920 Ma, and all Hengshan rocks underwent granulite-facies metamorphism at 1.88-1.85 Ga, followed by retrogression, sheafing and uplift. We interpret the Hengshan and adjacent Fuping granitoid gneisses as the lower, plutonic, part of a late Archaean to early Palaeoproterozoic Japan-type magmatic arc, with the upper, volcanic part represented by the nearby Wutai complex. Components of this arc may have evolved at a continental margin as indicated by the 2.7 Ga zircons. Major deformation and HP metamorphism occurred in the late Palaeoproterozoic during the Luliang orogeny when the Eastern and Western blocks of the North China Craton collided to form the Trans-North China orogen. Shear zones in the Hengshan are interpreted as major lower crustal discontinuities post-dating the peak of HP metamorphism, and we suggest that they formed during orogenic collapse and uplift of the Hengshan complex in the late Palaeoproterozoic （〈1.85 Ga）.

Positive and negative terrains on northern Shaanxi Loess Plateau

The Loess positive and negative terrains （P-N terrains）, which are widely distributed on the Loess Plateau, are discussed for the first time by introducing its characteristic, demarcation as well as extraction method from high-resolution Digital Elevation Models. Using 5 m-resolution DEMs as original test data, P-N terrains of 48 geomorphological units in different parts of Shaanxi Loess Plateau are extracted accurately. Then six indicators for depicting the geomorphologic landscape and spatial configuration characteristic of P-N terrains are proposed. The spatial distribution rules of these indicators and the relationship between the P-N terrains and Loess relief are discussed for further understanding of Loess landforms. Finally, with the integration of P-N terrains and traditional terrain indices, a series of un-supervised classification methods are applied to make a proper landform classification in northern Shaanxi. Results show that P-N terrains are an effect clue to reveal energy and substance distribution rules on the Loess Plateau. A continuous change of P-N terrains from south to north in Shaanxi Loess Plateau shows an obvious spatial difference of Loess land-forms and the positive terrain area only accounted for 60.5% in this region. The P-N terrains participant landform classification method increases validity of the result, especially in the Loess tableland, Loess tableland-ridge and the Loess low-hill area. This research is significant on the study of Loess landforms with the Digital Terrains Analysis methods.