Positional accuracy improvement: a comparative study in Shanghai,China

With the rapid development of geospatial data capture technologies such as the Global Positioning System, more and higher accuracy data are now readily available to upgrade existing spatial datasets having lower accuracy using positional accuracy improvement (PAI) methods. Such methods may not achieve survey-accurate spatial datasets but can contribute to significant improvements in positional accuracy in a cost-effective manner. This article addresses a comparative study on PAI methods with applications to improve the spatial accuracy of the digital cadastral for Shanghai. Four critical issues are investigated: (1) the choice of improvement model in PAI adjustment; five PAI models are presented, namely the translation, scale and translation, similarity, affine, and second-order polynomial models; (2) the choice of estimation method in PAI adjustment; three estimation methods in PAI adjustment are proposed, namely the classical least squares (LS) adjustment, which assumes that only the observation vector contains error, the general least squares (GLS) adjustment, which regards both the ground and map coordinates of control points as observations with errors, and the total least squares (TLS) adjustment, which takes the errors in both the observation vector and the design matrix into account; (3) the impact of the configuration of ground control points (GCPs) on the result of PAI adjustment; 12 scenarios of GCP configurations are tested, including different numbers and distributions of GCPs; and (4) the deformation of geometric shape by the above-mentioned transformation models is presented in terms of area and perimeter.

The empirical experiment results for six test blocks in Shanghai demonstrated the following. (1) The translation model hardly improves the positional accuracy because it accounts only for the shift error within digital datasets. The other four models (i.e., the scale and translation, similarity, affine, and second-order polynomial models) significantly improve the positional accuracy, which is assessed at checkpoints (CKPs) by calculating the difference between the updated coordinates transformed from the map coordinates and the surveyed coordinates. On the basis of the refined Akaike information criterion, the two best optimal transformation models for PAI are determined as the scale and translation and affine transformation models. (2) The weighted sum of square errors obtained using the GLS and TLS methods are much less than those obtained using the classical least squares method. The result indicates that both the GLS and TLS estimation methods can achieve greater reliability and accuracy in PAI adjustment. (3) The configuration of GCPs has a considerable effect on the result of PAI adjustment. Thus, an optimal configuration scheme of GCPs is determined to obtain the highest positional accuracy in the study area. (4) Compared with the deformations of geometric shapes caused by the transformation models, the scale and translation model is found to be the best model for the study area.     

基于局部相似的地籍宗地图斑匹配方法

地籍管理工作中,不同来源的宗地数据通常存在着诸多差异,识别和匹配不同数据源中的同名宗地图斑是提高数据更新精度与速度的关键,对地籍数据库的集成与信息共享有着非常重要的意义。该文针对地籍数据中宗地图斑的形状及变化特点,提出了一种基于局部相似的简单而有效的匹配方法来提高匹配率,基本原理是通过搜索两个面实体间最优的点对应或特征对应关系判断两个面实体是否匹配,采用形状相似度作为局部相似的判断指标。     

地籍实体的时间变化过程分析

宗地、土地证书和权利人是地籍信息系统中最基本的两个实体,宗地是土地证书的客体,权利人是土地证书的主体。宗地实体的生命周期实际上就是宗地空间形状及空间拓扑关系不发生变化的时间范围,土地证书的生命周期就是指土地证书客体以及土地证书主体都不发生变化的时间范围。在探讨地籍实体变更规律基础上,本文设计和研究了利用地理信息系统技术和数据库技术记录和回溯地籍实体随时间变化的方法。为地籍信息系统解决历史地籍信息管理提供了理论和技术基础     

Lots for greening: Identification of metropolitan vacant land and its potential use for cooling and agriculture in Phoenix,AZ, USA

The greening of vacant parcels for urban sustainability continues to gain attention from researchers and practitioners, including its use to ameliorate the urban heat island effect and food deserts. Planning for such uses requires accurate inventories of the amount and distribution of vacant parcels, which may prove difficult to produce for large, sprawling urban complexes. This study provides a systematic approach that combines remote sensing and cadastral data to distinguish different forms of vacant land for the Phoenix, Arizona metropolitan area while reducing computation time. The approach identifies vacant parcels for potential greening, focusing on privately owned land lacking buildings and impervious surfaces. The results for the Phoenix area reveal hot spots of these parcels, many of which reside along the fringe of the metropolis awaiting development. A large number of vacant parcels, however, reside within the metropolitan core and are suitable for greening as well, potentially serving to mitigate the urban heat island effect and food deserts in this region. The identification method and parcel results are detailed.     

Positional uncertainty in manually digitized map data

Digital map coordinates represent the locations of real world entities. As such, differences can exist between the ‘tru’ and digital database coordinates of those entities. This paper reports on a statistical characterization of positional error in manually-digitized and map-registered point data, the relative contribution of point type and operator to digitization error, and the effects of map media type on the positional uncertainty associated with registration.

Manually-digitized point data were collected by four operators from mylar and paper maps. Point locations for a number of different feature types were sampled from United States Geological Survey (USGS) 1:24 000 scale maps. Linear models were used to estimate the variance components due to among-operator, map media, point type and registration effects. The statistical distribution of signed distance deviations for manually-digitized data was leptokurtic relative to a random normal variate. Unsigned deviations averaged 0-054 mm. Squared distance deviations were not different from a Chi-square random variate. Variance components indicate that among-operator differences in positional uncertainty were large and statistically significant, while differences among point type were small and non-significant. Signed distance deviations associated with a first-order afhne followed a normal distribution. Unsigned distance deviations associated with a first-order affinc transformation averaged 0068mm, and squared distance deviations were distributed as a Chi-square. Differences in transformation accuracy were not related to type of map media.     

Simulating urban growth under planning policies through parcel-based cellular automata (ParCA) model

In recent decades, the cellular automata model, among the urban development prediction models, has been applied considerably. Studies show that the output of conventional cellular automata models is sensitive to cell size and neighborhood structure, and varies with changes in the size of these parameters. To solve this problem, vector-based cellular automata models have been introduced which have overcome the mentioned limitations and presented better results. The aim of this study was to present a parcel-based cellular automata (ParCA) model for simulating urban growth under planning policies. In this model, undeveloped areas are first subdivided into smaller parcels, based on some geometric parameters; then, neighborhood effect of parcels is defined in a radial structure, based on a weighted function of distance, area, land-use, and service level of irregular cadastral parcels. After that, neighborhood effect is evaluated using three components, including compactness, dependency and compatibility. The presented model was implemented and analyzed using data from municipal region 22 of Tehran. The obtained results indicated the high ability of ParCA model in allocating various land-uses to parcels in the appropriateness of the layout of different land-uses. This model can be used in decision-making and urban land-use planning activities, since it provides the possibility of allocating different urban land-use types and assessing different urban-growth scenarios.     

Seamless multivariate affine error-in-variables transformation and its application to map rectification

Affine transformation that allows the axis-specific rotations and scalars to capture the more transformation details has been extensively applied in a variety of geospatial fields. In tradition, the computation of affine parameters and the transformation of non-common points are individually implemented, in which the coordinate errors only of the target system are taken into account although the coordinates in both target and source systems are inevitably contaminated by random errors. In this article, we propose the seamless affine error-in-variables (EIV) transformation model that computes the affine parameters and transforms the non-common points simultaneously, importantly taking into account the errors of all coordinates in both datum systems. Since the errors in coefficient matrix are involved, the seamless affine EIV model is nonlinear. We then derive its least squares iterative solution based on the Euler–Lagrange minimization method. As a case study, we apply the proposed seamless affine EIV model to the map rectification. The transformation accuracy is improved by up to 40%, compared with the traditional affine method. Naturally, the presented seamless affine EIV model can be applied to any application where the transformation estimation of points fields in the different systems is involved, for instance, the geodetic datum transformation, the remote sensing image matching, and the LiDAR point registration.     

地理数据线性回归中的稳健估计方法

在线性回归中，常用最小二乘估计求线性方程的回归系数。但最小二乘估计受异常值影响较大，当样本数据存在异常值时，估计出的回归系数会产生较大偏差。稳健估计是最小二乘估计的改进，能在不排除异常数据的情况下，达到减弱异常数据对结果的影响。利用稳健估计提出黄土地区沟谷密度与侵蚀量的回归方程，并和最小二乘估计得到的回归方程比较，前者具有更回归效果。     

Relationships of Louisiana Colonial Land Claims with Potential Natural Vegetation and Historic Standing Structures: A GIS Approach*

Louisiana's French, Spanish, and British colonial administrations left a vivid imprint on the landscape in the form of unique cadastral survey systems. The collective distribution of these colonial land claims presents a picture of the colonial occupation of the state. Settlement shows up clearly along the waterways of the bayou state. Equally significant are the areas devoid of land claims. This paper discusses the compilation of the colonial Louisiana land claims map and demonstrates its utility to GIS-based historical geography and historic preservation. By merging this map with other digitized datasets such as potential natural vegetation and historic structures, the seemingly chaotic 18th century occupance of an extremely heterogeneous physical environment becomes patterned, and prior assumptions about the colonial settlement process may be tested with greater precision.     

Bias in the estimate of seismic moment tensor by the linear inversion method

Summary. We investigate the effects of various sources of error on the estimation of the seismic moment tensor using a linear least squares inversion on surface wave complex spectra. A series of numerical experiments involving synthetic data subjected to controlled error contamination are used to demonstrate the effects. Random errors are seen to enter additively or multiplicitively into the complex spectra. We show that random additive errors due to background recording noise do not pose difficulties for recovering reliable estimates of the moment tensor. On the other hand, multiplicative errors from a variety of sources, such as focusing, multipathing, or epicentre mislocation, may lead to significant overestimation or underestimation of the tensor elements and in general cause the estimates to be less reliable.     

1∶35万《库姆塔格沙漠地貌图》的编制

沙漠地貌图是认识和研究沙漠的基础图件,编制《库姆塔格沙漠地貌图》是国家科技基础性工作专项“库姆塔格沙漠综合科学考察”内容之一。本文全面总结了《库姆塔格沙漠地貌图》编制的思路和技术。考虑到库姆塔格沙漠地貌类型、分布规律及其形成和演变的需要,以及印刷纸张规格的限定,《库姆塔格沙漠地貌图》比例尺确定为1∶35万。选用的地理基础底图为20世纪70年代的1∶25万地形图,并以1∶10万地形图上作等高线和其他重要地理内容的补充。专题内容以2000—2007年的TM卫星数据为主,部分细节内容以Google Earth影像资料作补充。地貌图专题内容包含地貌类型、高度以及活动性等3层信息。地貌类型包括风成地貌、流水地貌、干燥剥蚀地貌、冰川冰缘地貌以及其他地貌等5大类,其中风成地貌是《库姆塔格沙漠地貌图》重点展示的内容。风沙地貌共分为13种类型,以符号表示,沙丘高度通过分层设色表示,用箭头符号表示沙丘移动方向。为了真实反映沙丘类型及其排列规律,本图对主要沙丘（高度一般大于10 m）都是准确定位描绘,而由于制图比例尺的限制,对一些次要沙丘（高度一般小于10 m）未作定位描绘,仅作示意。由于库姆塔格沙漠发育于阿尔金山北麓的倾斜洪积平原上,所以,洪积扇和干河道也是本图重点反映的内容。《库姆塔格沙漠地貌图》尽量应用现代计算机制图和数字化技术,对可以数字化的信息全部数字化。本图为研究库姆塔格沙漠提供了丰富信息。     

Trends of tropical deforestation in Southeast Mexico

We assessed deforestation in Southeast Mexico (a surface area of 29 000 km² in seven states) through the comparison of land use/land cover maps at a scale of 1:250 000. This facilitated mapping of the land use/land cover change (LULCC) processes and calculation of the rates of change and the change matrix for the period 1978–2000. An original method was used to assess the accuracy of the LULCC map. The verification sites were selected through a stratified random sampling and were corroborated with aerial photographs for 1978 and 2000. Error matrices were elaborated using both hard and fuzzy set approaches in order to take into account the errors related to generalization of the map in fragmented landscapes. The results showed an average annual deforestation rate of 1.1 per cent which represents an average annual loss of 190 000 ha of forest, or an estimated total reduction of 4.2 million ha over 22 years. Furthermore, deforestation processes are concentrated in some areas such as Yucatan and Chiapas states, which registered major forest conversions to grassland and slash‐burning. The overall accuracy of the LULCC map, assessed with hard and fuzzy set approaches, was 72 per cent and 88 per cent respectively.     

On the accuracy of TIGER-type geocoded address data in relation to cadastral and census areal units

In many applications of Geographical Information Systems (GIS) a common task is the conversion of addresses into grid coordinates. In many countries this is usually accomplished using address range TIGER-type files in conjunction with geocoding packages within a GIS. Improvements in GIS functionality and the storage capacity of large databases mean that the spatial investigation of data at the individual address level is now commonly performed. This process relies on the accuracy of the geocoding mechanism and this paper examines this accuracy in relation to cadastral records and census tracts. Results from a study of over 20 000 addresses in Sydney, Australia, using a TIGER-type geocoding process suggest that 5-7.5% (depending on geocoding method) of addresses may be misallocated to census tracts, and more than 50% may be given coordinates within the land parcel of a different property.     

地籍信息系统中动态地块存储的实现

该文归纳了地籍信息系统中地块动态变化的基本类型 ,提出了存储动态变化信息的两种解决方案 ,分别称之为基于多边形的数据结构和基于弧段的数据结构 ,讨论了它们具体的实现 ,并比较其优缺点     

北京市居住用地出让价格的空间格局及影响因素

以2004-2015年北京市六环内居住用地的交易样本为基本数据,借助ArcGIS、GS+、Surfer和Geoda软件,采用空间趋势面分析、最近邻指数（NNI）、探索性空间分析（ESDA）探讨居住用地出让和居住地价的空间格局特征,并对比OLS和空间回归模型（SLM和SEM）进一步探讨居住地价的影响因素。结果表明：① 北京市居住用地出让数量和出让面积不均衡,五六环间出让的居住用地最多。② 出让地块沿主要道路（如京石高速、京开高速、京沪高速及京藏高速）、地铁线（如地铁1号线、5号线、6号线、15号线、房山线、大兴线及亦庄线）呈轴线扩散,其中远郊区域这一特征更加明显。③ 居住地价从中心向外围总体表现“倒U型”趋势,且呈多中心圈层递减结构。④ 呈集聚分布模式,存在空间自相关,低值集聚区和高值集聚区明显。⑤ 模型对比方面,SLM>SEM>OLS,说明北京市居住地价存在实质性的空间依赖,而非干扰性的空间依赖。周边居住地块的价格、公交站、地铁站、重点小学、占地面积、容积率和出让方式对居住地价有显著影响。     

基于“城—村—地”三维视角的农村居民点整理策略——以江苏省新沂市为例

农村居民点作为当前国土资源利用效率提升的重要潜力空间,对其进行调控研究是促进可持续乡村建设的重要内容。城镇作为区域社会经济文化中心,村城关系在一定程度上影响着农村居民点发展的空间潜力;土地作为农村居民点发展的支撑条件和空间载体,村地关系在一定程度上体现了农村居民点布局的适宜性及资源利用的协调性。在扎实推进新农村建设、统筹城乡发展、促进土地集约节约利用的背景下,将“城—村—地”纳入统一分析框架,有利于统筹不同空间尺度要素对居民点整理的影响。本研究立足农村行为主体的空间关联性,综合“城—村—地”三级空间对象,提出农村居民点整理策略分析框架;基于对农村居民点地域系统要素构成和结构层次的分析,从城镇发展辐射性、村域布局适宜性、土地利用协调性等三方面构建了农村居民点整理潜力评价体系,进而探讨了相应的农村居民点整理途径。最后选取江苏省新沂市进行实证分析,将其划分为优先整理区、重点整理区、适度挖潜区、优化调整区及特殊整理区等居民点用地整理类型,提出相应的整理模式及优化路径,以期为农村居民点的整理优化提供有益借鉴,助推可持续的城乡空间重构。     

On the a priori estimation of collocation error covariance functions: a feasibility study

Error covariance estimates are necessary information for the combination of solutions resulting from different kinds of data or methods, or for the assimilation of new results in already existing solutions. Such a combination or assimilation process demands proper weighting of the data, in order for the combination to be optimal and the error estimates of the results realistic. One flexible method for the gravity field approximation is least-squares collocation leading to optimal solutions for the predicted quantities and their error covariance estimates. The drawback of this method is related to the current ability of computers in handling very large systems of linear equations produced by an equally large amount of available input data. This problem becomes more serious when error covariance estimates have to be simultaneously computed. Using numerical experiments aiming at revealing dependencies between error covariance estimates and given features of the input data we investigate the possibility of a straightforward estimation of error covariance functions exploiting known characteristics of the observations. The experiments using gravity anomalies for the computation of geoid heights and the associated error covariance functions were conducted in the Arctic region north of 64° latitude. The correlation between the known features of the data and the parameters variance and correlation length of the computed error covariance functions was estimated using multiple regression analysis. The results showed that a satisfactory a priori estimation of these parameters was not possible, at least in the area considered.     

建立省级数字高程模型(DEM)的关键技术——以江苏省为例

文章以江苏省的DEM制作为例,介绍利用ARCINFO、ARCVIEW软件生成DEM的全过程中的关键技术。应用结果表明,可以快速查找出采编地形图信息过程中的错误,建立的DEM精度较高,更适合于水土流失的定量监测,显示了该技术方法的可行性。     

Ecological compensation for winter wheat abandonment in groundwater over-exploited areas in the North China Plain

The land fallow policy was adopted by central and local governments to encourage the abandonment of water-intensive crops, such as winter wheat, in groundwater over-exploited areas. At the same time, since the 1990s, many households in the North China Plain (NCP) have chosen to replace the winter wheat and summer maize double-cropping system with the spring maize single-cropping system. Therefore, it is crucial to identify target land parcels for winter wheat abandonment and to design reasonable and proper standards for ecological compensation prior to the implementation of the land fallow policy in the NCP. In this study, multi-level logit models were used with household survey data in order to detect determinants across land parcel, household and village levels on household cropping system decisions; the opportunity costs for winter wheat abandonment were also calculated using cost–benefit analysis. The results show that: (1) land quality and irrigation condition at parcel level are two essential elements influencing household cropping system decisions. Nearly 70% of the total area of poor land and more than 90% of the total area of unirrigated land has suffered winter wheat abandonment. Target land parcels for the land fallow policy should be those that are irrigated and of high quality. (2) There were no significant differences between net profits from spring maize and summer maize under similar farming conditions, and the opportunity cost for winter wheat abandonment should be equal to the net profit of winter wheat. (3) The primary purpose of the land fallow policy is to induce groundwater recovery and restoration as a preliminary stage. A higher level of 350 yuan/mu is recommended as subsidy for ecological compensation at this stage. Later, the primary purpose of the policy should be a transition to a balance between exploitation and supplementation of water resources, and a lower level of 280 yuan/mu is recommended as a subsidy at this stage.