A map‐algebra‐based method for automatic change detection and spatial data updating across multiple scales

The availability of geospatial data has increased significantly over recent decades. As a result, the question of how to update spatial data across different scales has become an attractive topic. One promising strategy is to use an updated larger‐scale dataset as a reference for detecting and updating changed objects represented in a to‐be‐updated smaller‐scale dataset. For such an update method, an understanding of the different types of changes that can occur is crucial. Using polygonal building data as an example, this study examines the various possible changes from different perspectives, such as the reasons for their occurrence, the forms in which they manifest, and their effects on output. Then, we apply map algebra theory to establish a cartographic model for updating polygonal building data. Supported by concepts of map algebra, an update procedure involving change detection, filtering, and fusion is implemented through a series of set operations. In addition to traditional polygon overlay functions, the constrained Delaunay triangulation model and knowledge of map generalization procedures are employed to construct set operations. The proposed method has been validated through tests using real‐world data. The experimental results show that our method is effective for updating 1:10k map data using 1:2k map data.     

涡轮钻井技术在梨树断陷区块的应用

梨树断陷区块登娄库组、营城组、沙河子组、火石岭组地层可钻性差、岩性较致密、局部含砾严重,并且沙河子组局部层位岩石硬度达到7级,采用常规钻井技术,存在牙轮钻头效率低、寿命短等问题;各种型号PDC钻头试用后效果不理想。通过采用涡轮钻井技术,平均机械钻速提高了4倍,钻井周期缩短,钻井综合成本大大降低。实践证明,高速涡轮钻具＋孕镶金刚石钻井技术是高研磨性、高抗挤强度、高温地层深井钻进提速的有效技术。     

2021国际地理教育研究动态评议

2021年国际地理联合会地理教育委员会年会于2021年8月10日至13日在捷克首都布拉格成功举办,全球百余名地理教育研究者参与其中。此次会议由主题报告、分会场专题小组讨论会、研究海报展览和实地考察四个部分组成。主题报告和专题小组讨论等均围绕会议主题"建立联系:地理教育的合作与网络"展开,研究的热点议题聚焦地理知识的价值与意义、地理教师教育与培训和地理教育跨领域的合作。     

青藏高原地震活动及其构造背景

青藏高原是大陆范围内地质作用最活跃的地区。十分强烈的地震活动，清楚显示了以大区域构造为背景的整体性活动特征。在青藏高原的大地构造格局中来研究地震活动和震源性质的变化规律，是认识高原构造活动状态、规律、起因的重要部分。为此，本文综述了近些年该地区地震活动、震源性质、速度结构、地质构造及高原隆起机理的研究。     

Factors affecting runoff and sediment yield on the semiarid loess area in Northern Shaanxi Province,China

The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion in China. The Chinese government initiated the project “Grain-for-Green” for soil erosion control in 1999, with significant effect. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; therefore, the aim of this research was to investigate the effects of these four factors on runoff and soil loss at the runoff-plot scale over five years and use the Gray relational analysis methods to compare the impacts of these factors. Five runoff-measuring sites were established in five different vegetation types. The results show that the relative impacts of the four factors on runoff were: rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation. We also analyzed the weights of these four factors on runoff and sediment yield during the wettest year alone. For that year, the relative weights of the factors on runoff were topography > rainfall > soil > vegetation, and the relative weights of the factors on sediment yield were runoff > soil > rainfall > topography > vegetation.     

Broad area mapping of monthly soil erosion risk using fuzzy decision tree approach: integration of multi-source data within GIS

Soil erosion poses a serious problem for sustainable agriculture and the environment. There is a need to develop a simple and practical approach for broad area mapping of soil erosion risk that uses the uncertain but available information as input data within the constraints of reasonable cost and time. In this work, a predictive approach for conducting analytical erosion risk assessment across broad areas is developed, which combines a fuzzy decision tree (FDT), remote sensing and Geographic Information System (GIS). This approach is applicable to situations with a limited amount of input data and can easily adjust assessment factors according to actual need. In this study, four dominating factors affecting soil erosion were considered: soil, topography, land cover and climate. GIS thematic layers of these factors were constructed followed by fuzzified analysis through trapezoidal shaped membership functions. Based on subdivided erosion response units (ERUs), an optimal FDT was determined to classify monthly soil erosion risk into five levels. High-risk and very high-risk soil erosion in the study area is mainly concentrated from June to August, with July and August showing the highest risk covering more than 80% of the study area. November to March is dominated by low risk over more than 90% of the study area, while medium risk is dominant in April, May, September and October. Compared with field survey data, the fuzzy decision erosion risk assessment approach was shown to be applicable and economical for rapidly identifying and locating soil erosion risk with limited input data by means of remote sensing and GIS.     

Simulation of spatial population dynamics based on labor economics and multi-agent systems: a case study on a rapidly developing manufacturing metropolis

Spatial population dynamics affects resource allocation in urban planning. Simulation of population dynamics can provide useful information to urban planning for rapidly developing manufacturing metropolises. In such a metropolis with a concentration of immigrant labor forces, individual employment choices could have a significant effect on their residential decisions. There remains a need for an efficient method, which can simulate spatial population dynamics by considering the interactions between employment and residential choices. This article proposes an agent-based model for simulation of spatial population dynamics by addressing the influence of labor market on individual residential decisions. Labor economics theory is incorporated into a multi-agent system in this model. The long-term equilibrium process of labor market is established to define the interactions between labor supply and labor demand. An agent-based approach is adopted to simulate the economic behaviors and residential decisions of population individuals. The residential decisions of individuals would eventually have consequences on spatial population dynamics. The proposed model has been verified by the spatial dynamics simulation (2007 to 2010) of Dongguan, an emerging and renowned manufacturing metropolis in the Pearl River Delta, China. The results indicate that the simulated population size and spatial distribution of each town in Dongguan are close to those obtained from census data. The proposed model is also applied to predict spatial population dynamics based on two economic planning scenarios in Dongguan from 2010 to2015. The predicted results provide insights into the population dynamics of this fast-growing region.     

A vector field model to handle the displacement of multiple conflicts in building generalization

In map generalization, the displacement operation attempts to resolve proximity conflicts to guarantee map legibility. Owing to the limited representation space, conflicts may occur between both the same and different features under different contexts. A successful displacement should settle multiple conflicts, suppress the generation of secondary conflicts after moving some objects, and preserve the distribution patterns. The effect of displacement can be understood as a force that pushes related objects away with properties of propagation and distance decay. This study borrows the idea of vector fields from physics discipline and establishes a vector field model to handle the displacement of multiple conflicts in building generalization. A scalar field is first constructed based on a Delaunay triangulation skeleton to partition the buildings being examined (e.g., a street block). Then, we build a vector field to conduct displacement measurements through the detection of conflicts from multiple sources. The direction and magnitude of the displacement force are computed based on an iso-line model of vector field. The experiment shows that this global method can settle multiple conflicts and preserve the spatial relations and important building patterns.     

基于 GIS 的天津市突发性地质灾害预警预报系统设计与实现

基于地质灾害的多样性及其变化的随机性和非稳定性特点,本文综合利用数学算法和GIS技术,设计了地质灾害预警模型,分析了诱发地质灾害的地形、地貌、气象、水文等几方面的因素,应用地质灾害显式统计预警的基本原理,并通过确定性系数模型(CF)综合分析了天津市地质灾害分布与地质环境基础因素的关系,更好的修订了我市地质灾害预警预报模型.实践证明,应用基于GIS 的地质灾害预警预报系统已在我市近几年的地质灾害气象预警预报中不断完善,预警预报精度得到提高,防灾减灾效果明显,对保护人民生命财产安全发挥了重要作用.     

Spatio-temporal variation of net anthropogenic nitrogen inputs in the upper Yangtze River basin from 1990 to 2012

The net anthropogenic nitrogen input(NANI) is an important nutrient source that causes eutrophication in water bodies. Understanding the spatio-temporal variation of NANI is important for regional environment assessment and management.This paper calculated NANI in the upper Yangtze River basin(YRB), upstream of the Three Gorges Dam(TGD), from1990 to 2012, and analyzed its spatio-temporal characteristics. Over the past 23 years of the study, the average annual NANI increased from 3200 kg N km~(-2) to 4931 kg N km~(-2). The major components were fertilizer N application, atmospheric N deposition,and net food and feed N import. In the northwest high mountainous region with a sparse population, the main component was atmospheric N deposition. Fertilizer N application and net food and feed N import were concentrated in the Chengdu Plain because of the high population density and large areas of farmland. This research found that NANI increased with rapid urbanization and increasing population. The Pearson correlation results illustrated that the spatial distributions of NANI and its major components were affected by land cover/use, agricultural GDP and total population. Increasing NANI has been the major cause of the degrading stream water quality over the past 20 years and is becoming a major threat to the water quality of the TGD reservoir.