数字高程模型精度评定的基本理论

在剖析随机误差与逼近误差区别的基础上 ,指出数字高程模型 (DEM)内插误差属于逼近误差 ,精度评价方法不应继续延用“中误差”概念 ,而应采用“逼近误差”,给出了常用 DEM内插方法的误差评定模型 ,分析了等高线间距对 DEM内插精度影响的作用机制 ,最后解释了 DEM精度分析中用“中误差”概念无法解释的几个问题。     

人造卫星目视跟踪打印经纬仪的改造

对云南天文台人造卫星目视跟踪打印经纬仪进行了改造。在望远镜的两轴上加装了高分辨率的园感应同步器，数显表，实现了数字显示。经过改造后的望远镜测角精度由原来±３０角秒提高到±１角秒；分划板刻线由原来２角分改进为１５角秒；静态定位精度优于２０角秒，比改造前的仪器提高了一个数量级。     

应用GPS/重力数据确定(似)大地水准面

作为GPS/重力边值问题理论及方法的应用,本文在对GPS/重力方法确定（似）大地水准面的原理进行简要介绍与分析的基础上,利用收集到的N区的702个GPS重力数据以及52个高精度的GPS水准数据,计算出该区域的似大地水准面. 通过拟合法和系统差直接改正法进行的精度分析表明,应用GPS/水准方法确定的该地区似大地水准面的精度达到厘米级.     

基于卫星高度计的全球大洋潮汐模式的准确度评估

依据152个深海验潮站与大洋岛屿地面验潮站观测得到的8个主要分潮(M2、S2、K1、O1、N2、K2、P1及Q1)调和常数,对现有7个全球大洋潮汐模式的准确度进行了检验,结果显示各模式在深海大洋区域均达到了比较高的准确度:M2分潮的潮高均方根偏差在1.0～1.3cm之间;8个分潮的和方根偏差在2.1～2.3cm之间,与早期的模式相比,准确度又有了进一步提高。还依据中国近海18个岛屿的调和常数对其中的5个大洋潮汐模式的准确度进行了检验,结果表明,M2分潮均方根偏差在4.4～10cm,明显高于大洋的均方根偏差。其中日本国家天文台的潮汐模式NAO99在中国近海的结果相对较准确。     

全站仪对边测量原理及精度分析

对边测量是全站仪的一种专项测量功能,它可用来间接测量两个不可通视点之间的水平距离。该方法设站灵活,操作简单,但其测量精度没有标注,需要通过计算求得。本文根据全站仪对边测量的基本原理,推导出对边测量的精度计算公式,通过实例计算,对其精度进行了分析,讨论了对边测量在测站改变时其精度变化的规律,提出了提高对边测量精度的方法。     

The comparison index: A tool for assessing the accuracy of image segmentation

Segmentation algorithms applied to remote sensing data provide valuable information about the size, distribution and context of landscape objects at a range of scales. However, there is a need for well-defined and robust validation tools to assessing the reliability of segmentation results. Such tools are required to assess whether image segments are based on ‘real’ objects, such as field boundaries, or on artefacts of the image segmentation algorithm. These tools can be used to improve the reliability of any land-use/land-cover classifications or landscape analyses that is based on the image segments.The validation algorithm developed in this paper aims to: (a) localize and quantify segmentation inaccuracies; and (b) allow the assessment of segmentation results on the whole. The first aim is achieved using object metrics that enable the quantification of topological and geometric object differences. The second aim is achieved by combining these object metrics into a ‘Comparison Index’, which allows a relative comparison of different segmentation results. The approach demonstrates how the Comparison Index CI can be used to guide trial-and-error techniques, enabling the identification of a segmentation scale H that is close to optimal. Once this scale has been identified a more detailed examination of the CI–H- diagrams can be used to identify precisely what H value and associated parameter settings will yield the most accurate image segmentation results.The procedure is applied to segmented Landsat scenes in an agricultural area in Saxony-Anhalt, Germany. The segmentations were generated using the ‘Fractal Net Evolution Approach’, which is implemented in the eCognition software.     

What is the difference between two maps? A remote senser’s view

In remote sensing, thematic map comparison is often undertaken on a per-pixel basis and based upon measures of classification agreement. Here, the degree of agreement between two thematic maps, and so the difference between the pair, was evaluated through visual and quantitative analyses for two scenarios. Quantitative assessments were based on basic site-specific measures of agreement that are used widely in accuracy assessment (e.g. the overall percentage of pixels with the same class label in each of the two maps and the kappa coefficient of agreement) as well as an information theory based approach that allows the degree of mutual or shared information to be assessed even if different classification schemes have been used to produce the maps. The results indicated that in the first map comparison scenario, focused on labelling, there was a fair degree of correspondence between the maps but with an overall difference in information content of ∼42%. In the second comparison scenario, focused on change in time, considerable change had occurred with a change in class label for ∼42% of the pixels. It was also apparent that global assessments masked local scale changes.     

单频GPS接收机在国土资源调查应用中的误差分析

单频GPS接收机在国土资源调查中的应用越来越普及，而它在定位中受到误差源的影响。文中介绍了GPS接收机的主要误差来源，分析了各种误差对准确定的影响程度，为实际工作中避免和削弱这些影响提供了可以借鉴的方法。     

GPS动态定位的初步研究

基于我们的车载 DGPS试验成果和 DDKIN动态载波相位测量数据处理软件,本文主要论述了 GPS 动态定位的下列技术问题:依据 GPS卫星给用户提供的 User Range Accuracy值,选择定位星座;顾及运动载体的特点,选用 GPS信号接收天线及其在载体上的安设位置;用 Trimvec Plus和DDKIN 软件,精细处理一秒数据率的动态载波相位测量数据。     

论铀矿地质与测量精度关系中的几个问题

本文从地质勘查与测量工作的关系方面,讨论了地形图比例尺的确定,剖面、钻孔测量及其储量计算对测量精度的要求。