Building segmentation and outline extraction from UAV image-derived point clouds by a line growing algorithm

ABSTRACT

This paper presents an approach to process raw unmanned aircraft vehicle (UAV) image-derived point clouds for automatically detecting, segmenting and regularizing buildings of complex urban landscapes. For regularizing, we mean the extraction of the building footprints with precise position and details. In the first step, vegetation points were extracted using a support vector machine (SVM) classifier based on vegetation indexes calculated from color information, then the traditional hierarchical stripping classification method was applied to classify and segment individual buildings. In the second step, we first determined the building boundary points with a modified convex hull algorithm. Then, we further segmented these points such that each point was assigned to a fitting line using a line growing algorithm. Then, two mutually perpendicular directions of each individual building were determined through a W-k-means clustering algorithm which used the slop information and principal direction constraints. Eventually, the building edges were regularized to form the final building footprints. Qualitative and quantitative measures were used to evaluate the performance of the proposed approach by comparing the digitized results from ortho images.     

Orthopyroxene–cordierite mafic gneiss from the Nomamisaki metamorphic rocks,Southern Kyushu,Japan: Implication for western continuation of the Usuki–Yatsushiro Tectonic Line

We describe an orthopyroxene–cordierite mafic gneiss from the Nomamisaki metamorphic rocks in the Noma Peninsula, southern Kyushu, Japan. The mineral assemblage of the gneiss is orthopyroxene, cordierite, biotite, plagioclase, and ilmenite. Thermometry based on the Fe–Mg exchange reaction between orthopyroxene and biotite yields a peak metamorphic temperature of 680°C. The stability of cordierite relative to garnet, quartz, and sillimanite defines the upper limit of the peak metamorphic pressure as 4.4 kbar. These features indicate that the Nomamisaki metamorphic rocks underwent low‐pressure high‐temperature type metamorphism. Although a chronological problem still remains, the Nomamisaki metamorphic rocks can be regarded as a western continuation of the Higo Belt. The Usuki–Yatsushiro Tectonic Line, which delineates the southern border of the Higo Belt, is therefore located on the east of the Nomamisaki metamorphic rocks in southern Kyushu.     

滇东北一次飑线过程的中尺度结构特征

利用常规观测资料、卫星云图和多普勒天气雷达资料,综合分析了2007年6月14日发生在滇东北的一次飑线过程。结果表明:飑线发生在700 hPa切变线前和冷锋前暖区中,位于高层冷舌和低层暖舌相叠置的地区,高层冷空气侵入和地面中尺度切变线的触发作用是飑线形成和发展的主要动力过程。飑线前沿形成含有5个强单体的带状强回波,成熟阶段的强单体出现了弓形回波特征。飑线前沿出现低层辐合、中层径向辐合和高层辐散的特征,低层β中尺度辐合线随高度增加向飑线后部倾斜。飑线前沿存在前侧低层入流、中高层出流急流以及后侧低层入流急流。飑线上存在深厚的上升气流,两侧为下沉气流,且前方的下沉气流比后方强。低层强垂直风切变有利于飑线的产生和发展。     

新疆一次强飑线过程双多普勒雷达观测的中尺度风场结构分析

利用新疆乌鲁木齐和五家渠的双多普勒雷达同步观测资料与双多普勒雷达风场反演技术,结合多种气象资料(1 min间隔的地面自动站资料、探空资料和NCEP再分析场资料等),综合分析了2005年6月26日新疆乌鲁木齐附近一次强飑线过程。其流场特征是低层存在明显的辐合线,中层辐合,高层辐散。中低层的风场辐合使旧回波右侧(西南侧)一定距离处依次生成新回波并与旧回波合并,对流单体间的辐合线促使其迅速合并,是飑线发展的重要原因。对流单体间的合并是从中层开始的,然后扩展到低层。在低层对流单体合并后,飑线前部有一明显的辐合线,入流区、大的回波强度梯度区和弱回波区非常明显;同时,不同发展阶段的风场配置有明显的不同,上升气流和下沉气流在多单体风暴中同时存在。本次飑线过程中低层是东南风的入流气流,与对流带后部的西北风气流相遇后向上倾斜上升,在中高层形成飑前砧状云,这与国内外中纬度飑线的结构基本一致,但本次飑线过程只有前缘强烈的对流区,没有尾随的层状云降水。自动气象站、多普勒雷达及其反演的风场很好地揭示了该飑线的发生、发展、爆发过程及其回波和风场的空间结构特点。     

Recognition of shear heating on a long‐lived major fault using Raman carbonaceous material thermometry: implications for strength and displacement history of the MTL,SW Japan

The extent to which movement on major faults causes long term shear heating is a contentious issue and an important aspect in the debate about the strength of major faults in the crust. Comparing the results of experimental work on the kinetics of crystallization of carbonaceous material with results of thermal modeling show that the Raman carbonaceous material (CM) geothermometer is well suited to studying shear heating on geological time scales in suitable lithologies exposed around exhumed major fault zones. The Median Tectonic Line (MTL), SW Japan, is the largest on‐land fault in Japan with a length of > 800 km. Application of Raman CM thermometry to pelitic schist adjacent to the fault reveals the presence of a rise in peak temperature of around 60 °C over a distance of around 150 m perpendicular to the MTL fault plane. The spatial association of this thermal anomaly with the fault implies it is due to shear heating. Thermal modeling shows the recorded thermal anomaly and steep temperature gradient is compatible with very high rates of displacement over time scales of a few thousand years. However, the implied displacement rates lie outside those generally observed. An alternative explanation is that an originally broader thermal anomaly that developed during strike slip faulting was shortened due to the effects of normal faulting. Constraints on displacement rate, width of the original anomaly, duration of heating and peak temperature imply a coefficient of friction, μ, greater than 0.4.     

Podolian,Saxonian and baltic plates – Teisseyre–Tornquist Line and the edge of the East European Craton

In the area of the Central Europe three large continental scale tectonic units meet together, namely Precambrian East European Craton (EEC) to the northeast, Variscan West European Platform (WEP) terranes to the southwest, and younger Alpine Carpathian arc in the south. The reference structure of the Central Europe is a sharp edge of the East European Craton. In the area of Poland the south-western margin of the EEC is marked as Teisseyre–Tornquist Zone (TTZ), which continues to the north as Sorgenfrei–Tornquist Zone (STZ). Teisseyre–Tornquist Zone (TTZ) — earlier Teisseyre Line, Tornquist Line or Teisseyre–Tornquist Line (TTL), is a term created in commemoration of Polish geologist Wawrzyniec Teisseyre and German geologist and paleontologist Alexander Tornquist. At the turn of XIX and XX century, they noticed a fundamental difference in the geology of platform cover between the rigid East European Platform and its more mobile southwestern forefield (Teisseyre, 1893, 1903; Tornquist, 1908, 1910). From the very beginning the TTL was conceived as a linear feature (fault or fault zone) marking the southwestern boundary of the EEC. Contrarily, the Trans–European Suture Zone (TESZ) is a term coined by Asger Berthelsen for an assemblage of suspect terranes boarded by the East European Craton and the Variscan orogeny. It is not a linear structure, but a terrane accretion zone, 100–200 km wide. Both terms, TTL and TESZ, should not be mistaken, as is the case on many maps concerning the problem (Dadlez et al., 2005). The edge of the craton is a major lithospheric structure, which appears to be a deep-seated boundary reaching at least down to a depth of about 200 km as shown by tomographic analysis of shear wave velocity structure of the mantle under Europe. Another indication of the deep-seated nature of this zone was obtained from observations of earthquakes and explosions located in Europe. To explain the observed blockage of energy from regional seismic events by TTZ, the structural anomaly between eastern and western Europe must reach at least down to a depth of about 200 km. Continental scale tectonic units of the Central Europe are clearly visible in the crustal structure, Moho depth map, and also gravity, magnetic and heat flow maps.     

太阳大气中矢量磁场信息的推导

一种能从观测到的斯托克斯轮廓中提取太阳表面矢量磁场信息的方法在本文中提出，它利用斯托克斯轮廓非线心的极值点处相应参量对波长的导数为零这一数学事实，假设表面附近磁场矢量及热力学参量的变化梯度足够小以致所考虑的极值点的波长位置不随深度改变或此变化呆忽则使得偏振辐射围方程组得到极大的简化；再应用数值方法从此简化方程组中解出辐射表面附近的磁场矢量参数。通过拟合理论轮廓表明该法确实可以得到表面近似的磁场矢量     

Spectroscopic observations of PU vulpeculae and its binary nature

The peculiar nova-like star PU Vul was observed spectroscopically from 1981 Sept 12 to 1983 Dec 11 at Yunnan Observatory and Beijing Observatory. In 1981 Sept, the star showed an absorption spectrum of the Balmer lines, the H,K and D lines, and some FeII, SrII and TiII lines. H was seen in emission in 1982 Oct and Hβ, in 1983 Sept. Both emissions were enhanced in 1983 Oct. and then dimmed since 1983 Nov. On 1983 Dec 11, Hβ might be absent, but the H was still visible. The spectral type was similar to that of an F giant during this period. This object may be an exceptionally slow nova and a binary consisting of an M giant and a hot companion.     

春季气温异常与影响台州地区台风的关系

引　言台风影响台州地区时 ,往往对社会、经济的发展和人民的生命、财产带来严重的损失 ,当地领导对此十分重视。为此 ,每年临近台风季节 ,我们总是把台风的预报 ,特别是对台风的长期预报作为重中之重来抓。以往我们采用当年 1～ 3月份的降雪对应的韵律关系、回归方程和其它预报因子等工具来制作预报 ,但这些预报往往发生空报、漏报。现采用单站要素结合厄尔尼诺现象来预报有无影响台州地区的台风 ,取得了较好的预测效果。1　异常的春季气温与 8～ 9月份影响台州地区台风的关系1 1　厄尔尼诺 (不跨年度 )年春季气温与台风的关系每年 2月下…     

Les rhyolites hyperalcalines (pantellérites) du lac Tchad. Composition et signification tectonomagmatiqueThe peralkaline rhyolites (pantellerites) of the Lake Chad. Composition and tectonomagmatic significance

Remnants of rhyolite lava-dome and of alkaline microgranite extrusions emerge, as inselbergs, in the alluvial plain, south of Lake Chad. The peralkaline, arfvedsonite- and acmite-bearing rhyolites are determined as pantellerites. They can be related to a tectonomagmatic stage, dated of the Late Cretaceous, of the western central Africa rift system. They may constitute the NNE extension of a N50° to 30° elongated succession of small alkaline complexes, from the Gulf of Guinea to the North-Cameroon, which initiated the magmatic activity of the Cameroon Line. To cite this article: J.-P. Vicat et al., C. R. Geoscience 334 (2002) 885–891.