A topology-preserving polygon rasterization algorithm

Conventional algorithms for polygon rasterization are typically designed to maintain non-topological characteristics. Consequently, topological relationships, such as the adjacency between polygons, may also be lost or altered, creating topological errors. This paper proposes a topology-preserving polygon rasterization algorithm to avoid topological errors. Four types of topological error may occur during polygon rasterization. The algorithm starts from an initial polygon rasterization and uses a set of preserving strategies to increase topological accuracy. The count of the four types of error measures the topological errors of the conversion. Topological accuracy is summarized as 1 minus the ratio of actual topological errors to the total number of possible error cases. When applied to a land-use dataset with a data volume of 128 MB, 127,836 polygons, and extending 1352 km², the algorithm achieves a topological accuracy of more than 99% when raster cell size is 30 m or smaller (100% for 5 and 10 m). The effects of cell size, polygon shape, and number of iterations on topological accuracy are also examined.     

精密补偿器水准仪磁致误差及其测试方法

分析了精密补偿器水准仪磁致误差的成因，介绍了研制的一套磁致误差检测设备以及完整的检测方法。通过大量的检测数据与数理统计，表明４测回的标准差为０．００８″。该设备已为全国一等水准网复测，地震形变测量和精密工程测量等检测磁致误差１００多台次。     

����ƽ��ϵͳģ�����İ������������

????????????У????????????д???????????????????????????????????????????????????????????????????e??????????С????????????????????????????????R??????????????????????????????????????????????????????????????????С??????????????б?????????????????????????Ч??????????????д?????????????н?????????????     

顾及模型误差的卡尔曼滤波相位解缠

本文提出一种顾及模型误差的卡尔曼滤波相位解缠算法,该算法在卡尔曼滤波的状态空间模型中引入一与误差因素有关的控制变量,对相位误差进行补偿,通过在解缠过程中将卡尔曼滤波增益限制在一定范围内,把误差阻遏在相当小的区域,最后对解缠相位进行卡尔曼滤波平滑操作,减少了误差的传播.分别采用仿真数据和真实InSAR数据进行实验,并与原卡尔曼滤波相位解缠结果进行对比分析,验证了本文方法的有效性.     

PCA和KLE在高采样率GPS定位中的应用

为抑制多路径误差和随机噪声以提高定位精度,引入主成分分析（PCA）和KLE变换方法对定位坐标序列随机噪声水平进行评价、提取和消除多天坐标序列中的多路径误差。对比分析结果表明,主成分系数比值能有效地反映出强随机噪声对某天定位坐标序列的影响,PCA方法能有效地提取和消除多天定位坐标序列中的多路径误差,显著提高定位精度。KLE变换对随机噪声污染不敏感,对多路径误差的滤波能力较PCA略弱,但其对随机噪声以及局部异常具有较好的抑制作用。     

Characterizing errors in digital elevation models and estimating the financial costs of accuracy

Digital topographic models are the foundation of more advanced modeling applications and ultimately inform planning and decision making in many fields. Despite this, the error associated with these models and derived attributes is commonly overlooked. Little attention has been given in the scientific literature to the benefits gained from having less error in a model or to the corresponding cost associated with reducing model error by choosing one product over another. To address these gaps in knowledge we evaluated the error associated with five digital elevation models (DEMs) and derived attributes of slope and aspect relative to the same attributes derived from LiDAR data. We also estimated the acquisition and processing costs per square kilometer of the five test models and the LiDAR models. We used three measures to characterize model error: (1) root mean square error, (2) mean error (and standard deviation), and (3) area of significant elevation error. We applied these measures to DEM products that are used extensively across a range of applications for planning and managing natural resources. We depicted the relationship between model accuracy (the inverse of error) and cost in two ways. One was accuracy/cost ratio for each model. The other used separate data on accuracy and cost to better guide potential users in choosing between models or deciding on necessary expenditure on models. The main conclusion of our work was that accounting for error in DEMs can inform choice of models and the need for financial outlays.     

对海上高分辨率二维地震作业的认识

1994－1996年,广州海洋地质调查局承担了南海西部石油公司在北部湾的部分高分辨率二维地震调查工程,调查船使用设备为1993年从美国引进的OYO地震仪（型号为DAS－1）,施工过程前期进行了参数选择试验。本文介绍了高分辨地震调查参数选择依据、高分辨率二维采集中的一些注意事项、高分辨率二维采集中的一些注意事项、高分辨率地震资料的采集方法以及一些参数设定的原因。     

AR模型中AO类异常值探测及其在GPS卫星钟差预报中的应用

基于EM算法,提出一种AR模型中AO类异常值(additive outlier)探测的算法。该算法可同时进行AR模型拟合与AO类异常值探测,并可有效地解决成片AO类异常值探测时所产生的掩盖和淹没问题。最后,将本文算法应用于GPS卫星钟差预报之中。本文算法可以准确探测出钟差历史观测序列中的AO类异常值,并可对卫星钟差进行精确预报。     

不同实验条件下GPS伪距定位精度分析

研究概括了在不同的实验条件下利用GPS伪距获得较高精度定位结果的方法。实验结果的精度表明,这些方法的定位结果都能比常规的GPS伪距定位法的结果精度高,而且定位效果稳定。同时该方法也可为后续高精度定位及定轨等研究工作打好基础。     

高速铁路CPⅢ控制网测量误差来源及外业操作注意事项

简述了高速铁路控制测量相关的概念、CPⅢ控制网测量技术方案和CPⅢ控制网测量的误差来源,并结合在沪宁线几个月的作业实践经验,阐述了CPⅢ控制网测量时实际作业的注意事项。