A statistical approach to evaluating distance metrics and analog assignments for pollen records

The modern analog technique typically uses a distance metric to determine the dissimilarity between fossil and modern biological assemblages. Despite this quantitative approach, interpretation of distance metrics is usually qualitative and rules for selection of analogs tend to be ad hoc. We present a statistical tool, the receiver operating characteristic (ROC) curve, which provides a framework for identifying analogs from distance metrics. If modern assemblages are placed into groups (e.g., biomes), this method can (1) evaluate the ability of different distance metrics to distinguish among groups, (2) objectively identify thresholds of the distance metric for determining analogs, and (3) compute a likelihood ratio and a Bayesian probability that a modern group is an analog for an unknown (fossil) assemblage. Applied to a set of 1689 modern pollen assemblages from eastern North America classified into eight biomes, ROC analysis confirmed that the squared-chord distance (SCD) outperforms most other distance metrics. The optimal threshold increased when more dissimilar biomes were compared. The probability of an analog vs no-analog result (a likelihood ratio) increased sharply when SCD decreased below the optimal threshold, indicating a nonlinear relationship between SCD and the probability of analog. Probabilities of analog computed for a postglacial pollen record at Tannersville Bog (Pennsylvania, USA) identified transitions between biomes and periods of no analog.     

JX—3解析测图仪上航测高倍放大成图的试验

介绍试用１：３３０００比例尺航测资料，在ＪＸ－３解析测图仪上高倍放大航测１：１０００比例尺地形图的成图方案和应采取的技术措施，运用 解析法模型绝对定向的原理，在全野布点时采用两种方案对照比较，进行理论和试验精度的分析，并给出试验结果。     

佳木斯市GPS控制网的建立——索佳GSS1A型GPS接收机的应用

介绍利用日本索佳公司ＧＳＳ１Ａ型ＧＰＳ接收机在建立佳木斯市ＧＰＳ控制网中的应用。阐述了ＧＰＳ控制网的布设方案，外地施测方法和数据处理与精度分析，并扼要的总结了建网的经验与体会。     

SLJ型宽频带大动态力平衡三分向加速度计的设计与研制

文中详尽介绍了三分向力平衡加速度计的技术性能、工作原理和理论计算，给出了技术指标鉴定实测结果和获取地震记录的时程曲线。     

Accuracy analysis, dem generation and validation using russian tk-350 stereo-images

TK-350 stereo-scenes of the Zonguldak testfield in the north-west of Turkey have been analysed. The imagery had a base-to-height ratio of 0·52 and covered an area of 200 km × 300 km, with each pixel representing 10 m on the ground. Control points digitised from 1:25 000 scale topographic maps were used in the test. A bundle orientation was executed using the University of Hanover program BLUH and PCI Geomatica OrthoEngine AE software packages. Tests revealed that TK-350 stereo-images can yield 3D geopositioning to an accuracy of about 10 m in planimetry and 17 m in height. A 40 m resolution digital elevation model (DEM) was generated by the PCI system and compared against a reference DEM, which was derived from digitised contour lines provided by 1:25 000 scale topographic maps. This comparison showed that accuracy depends mainly on the surface structure and the slope of the local terrain. Root mean square errors in height were found to be about 27 and 39 m outside and inside forested areas, respectively. The matched DEM demonstrated a systematic shift against the reference DEM visible as an asymmetric shift in the frequency distribution. This is perhaps caused by the presence of vegetation and buildings.     

Methods for Setting up a Three-Dimensional Industrial Surveying System of “Building Blocks Type”

1　Methodsfororientatinginitialdirec tioninindustrialsurveyDifferentfromconventionalengineeringsurvey,thedistancebetweenthetwoangle measurementdevicesinindustrialsurveyisnomorethantenmeters.Theaccu racyforthemeasurementofobjectpointsisrequiredtobebetween± ( 0 .0 2～ 0 .0 5～ 0 .2 0 )mm ,sotheaccu racyfortheorientationoftheinitialdirectionoughttobehigh .Theexistingmethodsfororientatingtheinitialdirectionbetweenthetwoangle measurementdevicesincludemethodofusinginnertarget,collimatormethod,metho…     

无地面控制GPS辅助光束法区域网平差

介绍了在WGS-84坐标系中进行GPS辅助光束法区域网平差的基本原理以及利用大地水准面拟合方法实施大地高与正常高的变换方法。利用新疆库尔勒地区1：25000和1：50000实际航摄资料验证了理论与程序实现的正确性。试验结果表明，无地面控制GPS辅助光束法区域网平差可用于中小比例尺测图的加密，在WGS-84坐标系中可以获得较高的点定位精度，而在国家80坐标系下，利用大地水；隹面拟合前后的GPS摄站坐标进行GPS辅助光束法区域网平差，加密精度没有明显差异。     

导航卫星自主定轨的算法研究及模拟结果

讨论了利用卫星-卫星间的距离观测值建立导航卫星系统自主定轨的数学方法，并用GPS星座模拟星间观测值，采用滤波算法计算卫星的状态参数。模拟结果表明，在空间测距精度一定的情况下，自主定轨精度能高于GPS广播星历，因而能较精确地维持卫星系统的坐标框架。     

Stability and accuracy analysis of the central difference method for real‐time substructure testing

The central difference method (CDM) that is explicit for pseudo‐dynamic testing is also believed to be explicit for real‐time substructure testing (RST). However, to obtain the correct velocity dependent restoring force of the physical substructure being tested, the target velocity is required to be calculated as well as the displacement. The standard CDM provides only explicit target displacement but not explicit target velocity. This paper investigates the required modification of the standard central difference method when applied to RST and analyzes the stability and accuracy of the modified CDM for RST. Copyright © 2005 John Wiley & Sons, Ltd.