基于街景图像的可解释性城市感知模型研究方法

理解城市环境对人类感知的影响,对城市合理规划及布局具有重要的人文参考价值。城市环境是一个动态变化的复杂系统,具有空间异质性的特点。由于研究方法的限制,在复杂的城市环境中,以往基于街景图像的城市感知研究难以全面精细地分析环境关键要素对人类感知的影响。本研究以武汉市中心为研究区,首先利用全卷积神经网络将街景图像分割为城市地物类型,耦合感知打分数据和随机森林算法建立6类城市感知模型;然后基于沙普利值方法分解在随机森林模型中各类城市地物对人类感知的影响,并识别城市环境关键要素;最后结合分解结果,探究在非线性模型中沙普利值方法的适用性和优势。结果表明：沙普利值方法能够有效考虑环境异质性,精确地定量表示在不同场景中各类地物对人类感知的影响;城市高楼、天空、绿地空间是对人类感知影响最大的3类地物,且地物的体积和分布与其对人类感知的影响有关,图像占比大、分布连续的地物对人类感知的影响比图像占比小、分布离散的地物对人类感知的影响大;受城市环境空间异质性的影响,主要地物类型对各类感知的影响程度和形式有显著不同;高楼与人类感知为非线性关系,且具有明显的单调递增或递减的形式;绿地空间与积极感知呈非线性关系,与...     

Scalar Fluxes from Urban Street Canyons Part II: Model

A practical model is developed for the vertical flux of a scalar, such as heat, from an urban street canyon that accounts for variations of the flow and turbulence with canyon geometry. The model gives the magnitude and geometric dependence of the flux from each facet of the urban street canyon, and is shown to agree well with wind-tunnel measurements described in Part I. The geometric dependence of the flux from an urban street canyon is shown to be determined by two physical processes. Firstly, as the height-to-width ratio of the street canyon increases, so does the roughness length and displacement height of the surface. This increase leads to a reduction in the wind speed in the inertial sublayer above the street canyons. Since the speed of the circulations in the street are proportional to this inertial sublayer wind speed, the flux then reduces with the inertial sublayer wind speed. This process is dominant at low height-to-width ratios. Secondly, the character of the circulations within the street canyon also varies as the height-to-width ratio increases. The flow in the street is partitioned into a recirculation region and a ventilated region. When the street canyon has high height-to-width ratios the recirculation region occupies the whole street canyon and the wind speeds within the street are low. This tendency decreases the flux at high height-to-width ratios. These processes tend to reduce the flux density from the individual facets of the street canyon, when compared to the flux density from a horizontal surface of the same material. But the street canyon has an increased total surface area, which means that the total flux from the street canyon is larger than from a horizontal surface. The variations in scalar flux from an urban street canyon with geometry is over a factor of two, which means that the physical mechanisms responsible should be incorporated into energy balance models for urban areas.     

多平台点云数据的单木参数提取精度分析

以浙江省海宁市4种代表行道树(广玉兰、无患子、悬铃木、香樟树)为研究对象,结合无人机(UAV)影像和三维激光扫描数据,利用ContextCapture、LiDAR360软件完成点云拼接、滤波、降噪和编辑,通过迭代最近点算法实现点云精细匹配,完成多平台点云数据融合,进而得到数字表面模型与数字高程模型,并制作冠层高度模型;采用分水岭分割算法对不同行道树树种的冠层高度模型进行单木分割,并综合局部最大值法实现单木树高、冠幅的参数提取。结果表明,本文方法进行行道树单木分割的精度高,树高、冠幅参数提取值的效果好,满足行道树几何参数调查要求。     

How Many Facets are Needed to Represent the Surface Energy Balance of an Urban Area?

We investigate the question of how many facets are needed to represent the energy balance of an urban area by developing simplified 3-, 2- and 1-facet versions of a 4-facet energy balance model of two-dimensional streets and buildings. The 3-facet model simplifies the 4-facet model by averaging over the canyon orientation, which results in similar net shortwave and longwave balances for both wall facets, but maintains the asymmetry in the heat fluxes within the street canyon. For the 2-facet model, on the assumption that the wall and road temperatures are equal, the road and wall facets can be combined mathematically into a single street-canyon facet with effective values of the heat transfer coefficient, albedo, emissivity and thermodynamic properties, without further approximation. The 1-facet model requires the additional assumption that the roof temperature is also equal to the road and wall temperatures. Idealised simulations show that the geometry and material properties of the walls and road lead to a large heat capacity of the combined street canyon, whereas the roof behaves like a flat surface with low heat capacity. This means that the magnitude of the diurnal temperature variation of the street-canyon facets are broadly similar and much smaller than the diurnal temperature variation of the roof facets. Consequently, the approximation that the street-canyon facets have similar temperatures is sound, and the road and walls can be combined into a single facet. The roof behaves very differently and a separate roof facet is required. Consequently, the 2-facet model performs similarly to the 4-facet model, while the 1-facet model does not. The models are compared with previously published observations collected in Mexico City. Although the 3- and 2-facet models perform better than the 1-facet model, the present models are unable to represent the phase of the sensible heat flux. This result is consistent with previous model comparisons, and we argue that this feature of the data cannot be produced by a single column model. We conclude that a 2-facet model is necessary, and for numerical weather prediction sufficient, to model an urban surface, and that this conclusion is robust and therefore applicable to more general geometries.     

VORTEX MOTIONS IN THE ATMOSPHERIC CONVECTIVE BOUNDARY LAYER

Large vortices with scales ranging from hundreds meters to tens of kilometers are generallyfound in the atmospheric convective boundary layer(CBL).These vortices play important roles in the vertical transport of momentum,heat,water vaporand other tracers in the boundary layer.On the basis of the view of interaction between theconvection in CBL and the gravity waves in the upper stable layer the authors developed aconvection-wave theory on the formation of large vortices.According to the theory thewavenumber spectrum of the large vortices mainly depends on the atmospheric conditions in bothof the upper and lower layers,such as wind speed,wind direction shear,stratification as well astemperature jump.In the present paper satellite image and weather data in a case of cold air outbreak over warmocean are analyzed to study every stage of the convective processes,such as cloud street,convective cell as well as their transformation.According to the theory the wavenumbercompositions for cloud street and convective cell are calculated,respectively,on the basis of theatmospheric conditions at every stage.The distributions of vertical motions,convergent band anddisturbed interface are obtained and compared with the cloud patterns in the convective processes.Thus the study seems to offer a likely explanation for the origin of large vortices in CBL.     

Flow and Transport in the Obstacle Layer: First Results of the Micro-Scale Model MITRAS

A new atmospheric micro-scale chemistry, transport and stream model, MITRAS, has been developed within the Tropospheric Research Program (TFS). MITRAS is an obstacle resolving model solving simultaneously the governing equations for chemistry, pollutant transport including soot as well as for the flow and temperature field. The chemical reaction module is based on a simplified RACM mechanism. MITRAS has been tested against quality ensured wind tunnel data. The model results on soot and ozone concentrations as well as on the spatial representativeness of measurement sites underline the necessity for high-resolution flow simulations for case studies on close-to-source chemistry and pollutant transport within the urban canopy layer.     

二维街谷地面加热引起的流场特征的水槽实验研究

利用拖曳式水槽,采用激光粒子成像速度场测量系统(PIV),模拟了街谷存在地面加热时流场特征;讨论了环境风场对其的影响。我们发现在静风条件下,街谷中环流完全由热力驱动,对流活动可伸展至街谷上方;在建筑物层顶以上,也可发现水平和垂直方向的运动。这些对流活动有助于基本风场为零时,街谷内外动量和物质的交换。当街谷较宽时,对流形成的涡旋可能为两个以上,形态较为复杂并随时间变化,当街谷变窄时,涡旋蜕化成只有一个。当有弱环境风场存在时,街谷中的对流呈现为一个主涡旋,随着风速增加,涡旋形状更加规则,其中心并向下风向移动。     

城市专业化商业街空间分布特征及形成机理研究——以西安市为例

城市专业化商业街作为城市商业空间结构的组成部分,深刻影响着城市居民的生活空间.总结出专业化商业街的3种组织形式,并以西安市为例,分析了其空间形态及分布特征,指出其具有"一个核心,半条环线,线型形态,扇形对称,五大组团"的空间分布特征.进而,从交通、地价、历史沿革与大型结点四大物理要素出发,利用ArcGis软件,探讨了城市专业化商业街空间分布机理,得出:专业化商业街与城市次级交通峰值地带具有耦合特性,不同商业类型对租赁价格与商铺售价具有不同程度的依赖性,历史积淀及大型结点对城市商业街的形成也起着十分重要的作用.     

街景影像——基于人工智能的方法与应用

街景影像是感知城市物质环境的一种新型地理大数据.这种数据以人的视角详尽描绘了城市的可视环境,同时也隐性地表达了可视环境背后有关城市功能、社会经济和人类活动的信息.然而,传统的数字图像处理技术对街景影像的处理能力有限,不能高效地理解其中的语义信息.近年来,随着人工智能领域的不断发展,图像分析和机器学习方法取得了突破性的进...     

省级国土资源数据中心数据库命名规则研究

在对省级国土资源数据的多业务、多时相,多领域,海量性等特征分析的基础上,依据国家的相关标准与规范,对省级国土资源数据中心数据库分类体系进行了研究,将信息分类编码方法应用于国土资源数据中心数据库的分类编码工作,制订了适用于省级国土资源数据中心的数据库命名编码规则。