Quantitative evaluation of strategies for erosion control on a railway embankment batter

Strategies for erosion control on a railway embankment batter (side slope) are quantitatively evaluated in this paper. The strategies were centred on control (‘do nothing’ treatment), grass seeding, gypsum application, jute mat (an erosion control blanket) placement and planting hedgerows of Monto vetiver grass. Rainfall and runoff were monitored at 1 min intervals on 10 m wide embankment batter plots during 1998 and 1999. Total bedload and suspended sediment eroded from the plots were also measured but only for a group of storm events within sampling intervals. It has been demonstrated that vetiver grass is not cost‐effective in controlling erosion on railway batters within Central Queensland region. Seeding alone could cause 60% reduction in the erosion rate compared with the control treatment. Applying gypsum to the calcium‐deficient soil before seeding yielded an additional 25% reduction in the erosion rate. This is the result, primarily, of 100% grass cover establishment within seven months of sowing. Therefore, for railway embankment batter erosion control, the emphasis needs to be on rapid establishment of 100% grass cover. For rapid establishment of grass cover, irrigation is necessary during the initial stages of growth as the rainfall is unpredictable and the potential evaporation exceeds rainfall in the study region. The risk of seeds and fertilizers being washed out by short‐duration and high‐intensity rainfall events during the establishment phase may be reduced by the use of erosion control blankets on sections of the batters. Accidental burning of grasses on some plots caused serious erosion problems, resulting in very slow recovery of grass growth. It is therefore recommended that controlled burning of grasses on railway batters should be avoided to protect batters from being exposed to severe erosion. Copyright © 2001 John Wiley & Sons, Ltd.     

Research Paper. The predictive use of GIS to model property valuations

Abstract

GIS is a technology which is ideally suited to analysis of the market values of properties, since such values are based upon spatial comparisons as well as individual property attributes. Great Britain now has a new mechanism of local taxation, the council tax, which is based upon the capital values of properties. Central to the implementation of this tax has been the potentially controversial assignment of properties to valuation ‘bands’. This paper posits that a geographical model embedded within a GIS provides an alternative means of devising credible capital values, and anticipates some of the prospects for the use of GIS in local revenue-raising.     

The Seoul of Alonso: New Perspectives on Telecommuting and Residential Location from South Korea

Although theoretical studies have contended that telecommuting could cause residential relocation to peripheral areas, empirical evidence regarding this argument is scant and inconclusive. Moreover, previous studies have given little consideration to telecommuters' job locations. Using data from the 2006 Seoul Metropolitan Area Household Travel Survey, this study investigates the relationships between telecommuting and residential location, considering job location. Regression results suggest that telecommuter households are indeed more likely to reside in outlying areas, consistent with theory. However, this does not necessarily mean that telecommuting facilitates living in outlying areas, nor, conversely, that long commutes stimulate telecommuting: causality cannot be established with these data. But contrary to both hypotheses, the result partially arises from the fact that firms allowing telecommuting also tend to be located in peripheral areas, with telecommuters having shorter commute distances compared to office workers. Consequently, issues regarding telesprawl need to be discussed considering the distribution of telecommuting-conducive occupations.     

An efficient method for single-facility location and path-connecting problems in a cell map

This article presents an efficient method for simultaneously finding both the Weber cell and optimal connective paths in a grid. As numerous barriers of arbitrary shape and weighted regions are distributed in the cell map of this research, the problem scenario is similar to working out a real-life facility location selection and path-routing problems in a geographical map. In this study, the Weber problem of finding a single-facility location from an accumulation cost table is generated by a grid wave propagation method (higher-geometry maze router). After finding the Weber point (cell), optimal connective paths with minimum total weighted cost are backtracked between the Weber location cell and the demand cells. This new computation algorithm with linear time and space complexity can be integrated as a spatial analytical function within GIS.     

Rethinking Spatial Data Quality: Pokémon Go as a Case Study of Location Spoofing

The worldwide surge of the location-based game Pokémon Go since mid-2016 has raised debates among online gaming communities and the general public on the unique phenomenon of location spoofing. Location spoofing enables gamers to engage in remote activities by using simulated locational information. This has been largely considered a threat to the underlying fairness of the game and thus to the social order of both online game communities and the real world. This article takes up location spoofing as a unique case to engage the spatial data quality issue, an ever more fundamentally important issue in geography in today’s era of big data. Unlike the well-examined systematic error, outliers, and uncertainty in spatial data, our understanding of user-generated spatial data from location spoofing is rather limited. To fill this gap and advance the debates on the spatial data quality issue, we collected a data set of Pokémon and applied actor–network theory to examine the various human and nonhuman agents involved, including gamers, spoofers, game developers, bots, and hackers. We argue that location spoofing in mobile games and other increasingly location-based services (e.g., Uber) should not be merely interpreted as fake data but should be taken seriously as real human geographic data in new spatial (re)assemblages proliferating nowadays. We encourage scholars in geography and neighboring fields to investigate this emerging issue in location-based services, with the goal of promoting a more critical and holistic understanding of geospatial big data.     

Megaurbanization and Industrial Relocation in Mexico's Central Region

Recent changes involving Mexico City, the main metropolis in Mexico and one of the world's largest megacities, are a slowing demographic growth and the relocation of industrial activities from the city proper to other cities in the Central Region. One of the important features of this process is the extension of existing location economies for manufacturing industries from the strictly urban, or metropolitan scale, to a somewhat more regional level. This paper argues that this territorial restructuring is highly influenced by four main processes: (1) a spatially selective industrialization where a few cities, rural areas and economic corridors are emerging as industrial locations; (2) accessibility and transaction flows where the main road network and commodity flows determine the primary urban structure and the formation of economic corridors; (3) a concentrated pattern of foreign investment that shows a marked preference for the urban "core" and which reinforces its economic importance; (4) a territorial industrial specialization pattern whose main feature is a mixture of dispersion and concentration trends according to the type of manufacturing industry. Territorial restructuring in this region is an excellent example of an emerging spatial order associated to megaurbanization, with a rapid growth of nearby cities, a polycentric urban pattern, and the arrival of manufacturing industry in selective sites. However, this process seems to reinforce current intraregional inequalities, as the places with the best economic advantages tend to receive larger investments.     

The current status ofAtriplexon the Cape Verde Islands

Extensive areas of low lying coastal plains on Santiago Island, Republic of Cape Verde, are virtually devoid of natural vegetation. Of many introduced trees and shrubs, onlyAtriplexspecies have been found to thrive. Several plantations have been established during the past 15 years by the Cape Verde Government, FAO and other agricultural development groups. Results from these, together with local perceptions, indicate that although growth and survival are good, the primary objective of providing forage is not being met, owing to the unpalatability ofAtriplexto local stock. In recent field trials, severalAtriplexspecies showed good growth, but none were browsed and survival was quite poor, with onlyA. undulata(65%) andA. canescens(100%) exceeding 60% survival. Forage analysis identified high salt content in all species tested, and the highest protein content was found inA. glauca(16%),A. vesicaria(17%) andA. canescens(20%), which also had the lowest salt levels.Atriptex canescenswas identified as worthy of further introduction. An establishedA. halimusplantation that was observed to be browsed was compared to unbrowsed stands in terms of forage, soil and local drinking water analyses. Possible reasons for the unpalatability ofAtriplexto local stock and its resolution are discussed, along with the potential future ofAtriplexon the Cape Verde Islands.     

旅游集散地规划的地计算模型及案例

从地计算的角度出发,分析了地计算在旅游集散地规划中的问题,以江西上饶为例,运用可计算模型对旅游地域系统规划中的旅游中心集散地选择问题,旅游服务设施区位以及宾馆床位数的最优化问题进行了研究。这些问题的共同特征是它们是区域规划性质的、地理学的,而不是建筑学的景点景观设计。研究发现,地计算对于提高规划水平,是有效的,同时表明一般的空间分析问题,可以建立可计算模型。所有模型采用Visual Basic6.0(VB)编写程序实现计算,程序中调用了GIS软件中的MapObjects2.0控件实现地理显示、分析功能。这一工作显示VB与GIS软件结合,可以获取强大的空间分析功能。     

Seismicity features of the 1998 Luding, Sichuan earthquake sequence of ML=3.4

LongmenshanfaultzoneislocatedintheeasternedgeofTibetanplateaucollisionbeltdividingChinaintoeastandwestpart.ItisoneofthehighseismicityareasinSichuanProvince.TheDecember8,1998LudingearthquakesequenceofML=3.4occurredinthesouthofLongmenshanfaultzonewithmanyfullobservedrecords.Althoughthemagnitudesofthisearthquakesequencearenotverybig,thegeographiclocationsareveryimportant.BecausetheyarenearbytheintersectingareaofLongmenshanfaultwithXianshuihefaultandXiaojiangfault,wherethestructuresandtheregi…     

用相对定位法精细测定张北地震序列的时空参数

使用笔者改进了的相对地震定位方法对１９９８年１月１０日至５月３１日的张北地震序列中ＭＬ３．０级以上地震进行了重新测定,由于相对定位法能在一定程度上抵消地壳速度结构的横向不均匀性地震定位的影响,从而取得了较常规定位方法更精细的结果。