The compilation of a DTM and a new satellite image map for King George Island, Antarctica

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全球虚拟地形环境中Mipmap纹理技术研究

M ipm ap纹理技术是目前解决纹理分辨率与视点距离关系的最有效途径。将M ipm ap纹理引入全球虚拟地形环境的金字塔模型中,在分析现有M ipm ap纹理生成技术不足的基础上,提出了一种新的M ipm ap纹理生成技术,并针对M ipm ap纹理以多级形式存储会使数据量增加的问题,提出了M ipm ap纹理压缩算法,以提高实时渲染中M ipm ap纹理的装载速度和创建速度,并用实验结果验证了算法的可行性。最后给出了全球金字塔模型中M ipm ap压缩纹理的存储结构。     

基于零立体像对立体匹配的配后质量控制

立体匹配的质量控制对数字摄影测量产品的质量起着关键的作用。本文首先分析了现有的各种质量控制策略，然后根据正射影像同ＤＴＭ及匹配点位存在的固有关系，提出了用零立体像对再匹配作为立体匹配的配后质量控制方案，为立体匹配质量控制开辟了崭新的途径。     

ArcToolBox在1∶50000地形数据库动态更新中的应用

在1∶50000地形数据库动态更新的工作中,通过使用ArcGIS提供的ArcToolBox工具箱,进行辅助生产和质量控制,灵活高效地解决生产过程中的实际问题,确保1〖DK〗∶50000地形数据库动态更新项目顺利完成。     

基于1：10000地形数据更新1：50000DEM的研究试验

对1：50000DEM数据库的现状进行了分析,提出了利用1：10000地形数据更新1：50000DEM的主要内容和两种疗法．简要介绍了地形变化检测方法。通过时试验区规则格网DEM成果的精度检查验汪了方法的可行性。客观分析了本次试验的特点和不足,为以后大比例尺地形数据更新小比例尺DEM等相关工作提供了技术参考。     

Regional geoid modeling in the area of subglacial Lake Vostok,Antarctica

We present a geoid model for the area of Lake Vostok, Antarctica, from a combination of local airborne gravity, ice-surface and ice-thickness data and a lake bathymetry model. The topography data are used for residual terrain modeling (RTM) in a remove–restore approach together with GOCE satellite data. The quasigeoid is predicted by least-squares collocation (LSC) and subsequently converted to geoid heights. Special aspects of that method in presence of an ice sheet are discussed.It is well known that a body freely floating in water is in a state of hydrostatic equilibrium (HE). This usually applies, e.g., to ice shelves or sea ice. However, it has been shown that this is valid also for the ice sheet covering the subglacial Lake Vostok. Thus, we demonstrate the use of such a refined regional geoid model for glaciological and geophysical applications by means of the HE surface of that lake. The mean quadratic residual geoid signal (0.56 m) w.r.t. the GOCE background model exceeds the residual variations of the estimated apparent lake level (ALL) (0.26 m) within the central part of the lake. An approach considering the actual geopotential at the ALL has been derived and subsequently applied. In this context, downward continuation of the potential field within the ice sheet as well as the latitudinal tilt of off-geoid equipotential surfaces are discussed. In view of the accuracy of the ice-thickness measurements that dominate the total error budget of the estimated ALL these effects are negligible. Thus, the HE surface of subglacial lakes may safely be described by a constant height bias in small-scale regional applications. However, field continuation is significant with respect to the formal uncertainty of the quasigeoid, which is at the level of 5 cm given that accurate airborne gravity data (±2 mGal) are available.     

Eclogites preserved as pebbles in Jurassic conglomerate, Dabie Mountains, China

Two types of eclogite pebbles were discovered in Middle to Upper Jurassic conglomerates from the Hefei Basin north of the Dabie ultrahigh-pressure (UHP) terrain, China. Type A eclogite pebbles are characterized by idioblastic garnet with well preserved chemical zonation. Si content in phengite is lower than 3.5 per formula unit (pfu). The maximum metamorphic pressure is lower than 2.5 GPa, and the temperature is below 600 °C. Type B eclogite pebbles contain coesite pseudomorphs in xenoblastic garnet. Si content in phengite is higher than 3.5 pfu. The maximum metamorphic pressure is 2.8–4.0 GPa at 700 °C indicating UHP metamorphism.

Types A and B eclogite pebbles are comparable with eclogites occurring in the southern portion of the Dabie UHP terrain. Based on the petrologic similarities and northeastwards directed paleocurrents, we infer that the eclogite pebbles were eroded from the Dabie UHP terrain. Sandstones containing detrital phengite with Si content higher than 3.5 pfu are also derived from UHP rocks. These petrologic and stratigraphic data place time constraints on exhumation and erosion history of the Dabie UHP terrain.     

Evaluation of multisource data for glacier terrain mapping: a neural net approach

Spectrally similar nature of land covers in a glacierized terrain hampers their automated mapping from multispectral satellite data, which may be overcome by using multisource data. In the present study, an artificial neural network (ANN)-based information extraction approach was applied for mapping the Kolahoi glacier and adjoining areas, using Landsat TM (Thematic Mapper) data and several ancillary layers such as image transformations and topographic attributes. Results reveal that ANN (highest overall accuracy (OA): 83.74%) outperforms maximum likelihood classifier (highest OA: 66.90%) and the incorporation of ancillary data into the classification process significantly enhances the mapping accuracy (>9%), particularly the addition of Near Infrared Red/Short Wave Infrared (NIR/SWIR) data to the spectral data. A nine-band combination dataset (spectral data, slope, Red/NIR and decorrelation stretch) was found to be the best multisource dataset. Results of the Z-tests (at 95% confidence level) also corroborate and statistically validate the above findings.