Comparing the terrain reversal effect in satellite images and in shaded relief maps: an examination of the effects of color and texture on 3D shape perception from shading     

Arzu Çöltekin  Julien Biland 《International Journal of Digital Earth》2019,12(4):442-459

Terrain reversal effect (TRE) causes reversed 3D shape perception in satellite images and shaded relief maps (SRMs), and introduces difficulties in identifying landforms such as valleys and ridges. With this paper, in a controlled laboratory experiment, we compare how well 27 participants could identify valleys and ridges over 33 locations using SRMs, color satellite images and grayscale satellite images. The main depth cue is shadow both in vertical-view images and SRMs. However, the presence of texture and color in images also affect 3D shape perception. All our participants experience the illusion strongly: with the SRMs, it is very severe (2% accuracy), with grayscale images low but considerably better than SRMs (17.6% accuracy), and slightly worse with color imagery (15.3% accuracy). These differences between SRMs and imagery suggest that the participants who are able to bypass the illusion consciously or subconsciously interpret the photographic information. We support this observation further with a cue-strength analysis. Furthermore, we provide exploratory analyses of the effects of expertise, global convexity bias, and bistable perception. Our original empirical observations serve towards a better understanding of this visual illusion, and contribute towards nuanced and appropriate solutions to correcting for TRE differently for satellite images and SRMs.  相似文献   

陀螺经纬仪定向系统误差研究   总被引：2，自引：1，他引：1  

王庆林 《测绘科学》2010,35(5):56-57

通过对不同观测者用逆转点法进行的陀螺经纬仪定向实验数据分析,确认不同观测者在用逆转点法进行陀螺经纬仪定向时存在着显著的系统误差,而且这种系统误差的大小还随所使用的仪器不同而不同。研究结果对制定陀螺经纬仪定向操作程序和提高定向精度有一定的指导意义。  相似文献   

企鹅珍珠贝生殖细胞的发生     

徐宗芹  王梅芳  梁飞龙  余祥勇 《广东海洋大学学报》2009,29(6):32-35

对不同发育阶段的企鹅珍珠贝[Ptedapenguin(Rding)]的性腺结构、生殖细胞结构与分布进行组织学观察,描述精/卵子发生过程中各级精/卵细胞的特征。结果表明:根据雌性生殖细胞形态和卵黄的变化特点,卵子发生经历卵原细胞、无卵黄初级卵母细胞、卵黄形成期卵母细胞及成熟卵子阶段;依据雄性生殖细胞大小和细胞核形态变化,精子发生经历精原细胞、初级精母细胞、次级精母细胞、精子细胞和精子阶段,其中精原细胞存在形态上有差异的A型和B型两种类型。此外还观察到企鹅珍珠贝的性别转化现象。  相似文献   

新疆吐鲁番桃树园二叠-三叠系古地磁初步研究     

李永安  李锦玲  程政武  孙东江  刘俊  郑洁 《新疆地质》2004,22(2):136-142

通过对吐鲁番桃树园二叠—三叠系古地磁特征初步研究,建立了二叠—三叠系界线磁性层柱,将其界线置于锅底坑组中下部,即37—36层(采点66～65).对二叠、三叠系古地磁研究表明,其古纬度为北纬26°～35°,属热带—北温带古气候环境,与古生物资料和沉积相相一致,推断古生物灭绝与新生,可能与地磁的转化密切相关。  相似文献   

青藏高原末次快速隆升与“亚澳”陨击事件   总被引：11，自引：3，他引：11       下载免费PDF全文

葛肖虹  任收麦  刘永江  吴光大  袁四化 《第四纪研究》2004,24(1):67-73

黄土、山前磨拉石年代学最新研究成果表明青藏高原及其相邻山脉最晚一期,也是最强烈的隆升事件发生在早更新世晚期(0.9～0.8MaB.P.)。这是一次由于印度板块脉冲式陆内俯冲(A型)引起的“挤压隆升”,而不是重力均衡引起的“伸展隆升”。它对中亚及我国西部广袤区域盆-岭地貌的形成、盆地中-新生界构造变形和大范围的干旱与沙漠化起了决定性的影响。0.9～0.8MaB.P.期间发生在印度洋洋中脊三联点附近(67°E,20°S)的“亚澳”陨击事件,很可能是引起印度洋快速扩张、导致印度板块在锡瓦利克带强烈俯冲(A型),并引起了青藏高原0.9～0.8MaB.P.快速隆升的大陆动力学背景。其影响不止于印度洋周边,而且还涉及西南太平洋。0.9MaB.P.前后引起全球气候变化的“中更新世革命”(MPR)、“西太平洋暖池”的形成以及0.78MaB.P.布容期与松山期地磁极性倒转(BM界限)的发生都可能与此有关。  相似文献   

Numerical modelling of flow structures over idealized transverse aeolian dunes of varying geometry   总被引：2，自引：0，他引：2  

Daniel R. Parsons  Ian J. Walker  Giles F. S. Wiggs 《Geomorphology》2004,59(1-4):149

A Computational Fluid Dynamics (CFD) model (PHOENICS™ 3.5) previously validated for wind tunnel measurements is used to simulate the streamwise and vertical velocity flow fields over idealized transverse dunes of varying height (h) and stoss slope basal length (L). The model accurately reproduced patterns of: flow deceleration at the dune toe; stoss flow acceleration; vertical lift in the crest region; lee-side flow separation, re-attachment and reversal; and flow recovery distance. Results indicate that the flow field over transverse dunes is particularly sensitive to changes in dune height, with an increase in height resulting in flow deceleration at the toe, streamwise acceleration and vertical lift at the crest, and an increase in the extent of, and strength of reversed flows within, the lee-side separation cell. In general, the length of the separation zone varied from 3 to 15 h from the crest and increased over taller, steeper dunes. Similarly, the flow recovery distance ranged from 45 to >75 h and was more sensitive to changes in dune height. For the range of dune shapes investigated in this study, the differing effects of height and stoss slope length raise questions regarding the applicability of dune aspect ratio as a parameter for explaining airflow over transverse dunes. Evidence is also provided to support existing research on: streamline curvature and the maintenance of sand transport in the toe region; vertical lift in the crest region and its effect on grainfall delivery; relations between the turbulent shear layer and downward forcing of flow re-attachment; and extended flow recovery distances beyond the separation cell. Field validation is required to test these findings in natural settings. Future applications of the model will characterize turbulence and shear stress fields, examine the effects of more complex isolated dune forms and investigate flow over multiple dunes.  相似文献   

Trends in Cretaceous and Tertiary geomagnetic reversals     

R.A. Reyment 《Cretaceous Research》1980,1(1):27-48

The statistical theory of modulated renewal processes is used to analyze the polarity reversal scales of Larson & Hilde (1975) and LaBreque, Kent & Cande (1977). The results suggest that the trending effect in these data may be modelled by a rate parameter with an exponential quadratic trend. Short times in one polarity state tend to be followed by short times in the other state. The graphical analysis points to the possibility of an undulating pattern in reversal rates. The empirical distributions of the normal and reversed polarities show slight differences in comparison with each other in most of the statistical tests, but a moving-window analysis indicates possible serial effects for the normal times. As a rough approximation, a statistical two-state model for reversals might be realistic, for example, an alternating renewal process under relaxed assumptions. There has been a gradual stepping-up of the minimum reversal rate from the Oligocene to the present, but little change in the observed range of the reversal rates. With the long quiet (Mercanton) interval removed from the data, the average time spent in the reversed polarity state is slightly greater than for the normal state. A change in statistical properties for the entire set of data considered as a single sample occurs around the Eocene-Oligocene transition (Middle Eocene on earlier time scales). The analyses of the statistical second-order properties of the entire sequence of 271 observations, and the subsets of normal and reversed between-times, reject a renewal hypothesis if theoretical statistical considerations are strictly applied to the results (although this hypothesis is not rejected for the Oligocene to Recent observations); this result is at variance with some geophysical models. A short appendix on the theory of point processes is provided to aid the general reader in following the arguments used in this paper.  相似文献   

Dynamic instability of clays: an energy approach   总被引：1，自引：0，他引：1  

Eugene A. Voznesensky  Steinar Nordal 《Soil Dynamics and Earthquake Engineering》1999,18(2):601

The dynamic instability of any soil is based on the ability to accumulate from cycle to cycle a part of the energy to be dissipated. Using the general thermodynamic approach in combination with high resolution experiments it is possible to analyze the transformations of energy in soil under dynamic loading. Undisturbed specimens of two Norwegian clays, sufficiently different in their engineering properties, were used in a number of undrained cyclic triaxial tests to study the influence of confining stress, coefficient of earth pressure at rest (K₀), dynamic stress amplitude and frequency of loading in the development of instability in the clays. This paper discusses the unit dissipated energy and the unit activation energy as possible energy criteria for evaluation of dynamic instability in soils.  相似文献   

中生代地球系统与核—幔边界动力学研究进展   总被引：3，自引：1，他引：2  

邵济安  韩庆军 《地质论评》1998,44(4):382-388

本文介绍了９０年以来地球物理学在地球磁场方面的研究成果,揭示了２００－１００Ｍａ全球低的地球磁场古强度;１２４－８３Ｍａ低的极性反转频率以及１７０－１１０Ｍａ近乎停滞的真极移。  相似文献   

人工诱导巨石斑鱼性逆转的研究     

杨家驹  黄增岳  肖耀兴  李庆欣 《热带海洋学报》1996,(4)

采用雄性激素埋植法诱导巨石斑鱼Ｅｐｉｎｅｐｈｅｌｕｓｔａｕｖｉｎａ（Ｆｏｒｓｋａｌ）提早性逆转，使３－７龄成熟雌鱼在大约５０—９０ｄ内转变为功能性雄鱼，并成功地进行了人工授精繁殖，获得正常健壮仔鱼８万多尾。文中并就性逆转期间性腺、性细胞的发育和变化过程以及雄性激素的作用问题进行了讨论。  相似文献