Enabling point pattern analysis on spatial big data using cloud computing: optimizing and accelerating Ripley’s K function

Performing point pattern analysis using Ripley’s K function on point events of large size is computationally intensive as it involves massive point-wise comparisons, time-consuming edge effect correction weights calculation, and a large number of simulations. This article presented two strategies to optimize the algorithm for point pattern analysis using Ripley’s K function and utilized cloud computing to further accelerate the optimized algorithm. The first optimization sorted the points on their x and y coordinates and thus narrowed the scope of searching for neighboring points down to a rectangular area around each point in estimating K function. Using the actual study area in computing edge effect correction weights is essential to estimate an unbiased K function, but is very computationally intensive if the study area is of complex shape. The second optimization reused the previously computed weights to avoid repeating expensive weights calculation. The optimized algorithm was then parallelized using Open Multi-Processing (OpenMP) and hybrid Message Passing Interface (MPI)/OpenMP on the cloud computing platform. Performance testing showed that the optimizations effectively accelerated point pattern analysis using K function by a factor of 8 using both the sequential version and the OpenMP-parallel version of the optimized algorithm. While the OpenMP-based parallelization achieved good scalability with respect to the number of CPU cores utilized and the problem size, the hybrid MPI/OpenMP-based parallelization significantly shortened the time for estimating K function and performing simulations by utilizing computing resources on multiple computing nodes. Computational challenge imposed by point pattern analysis tasks on point events of large size involving a large number of simulations can be addressed by utilizing elastic, distributed cloud resources.     

Climate influences on water and sediment properties of Genovesa Crater Lake,Galápagos

Genovesa Crater Lake is a remote, hypersaline lake in the northern Galápagos archipelago that contains a finely laminated sediment record. This sediment record has the potential to provide a high-resolution history of past climate variability in the eastern tropical Pacific. Here we present modern climate, lake, and sediment observations from 2009 to 2012 to explore how local climate variability influences Genovesa Crater Lake and its sediments. Surface lake temperature is strongly linked to air temperature and is highly seasonal. Temperature stratification is strongest during the warm season, whereas temperature becomes more uniform through the water column in the cool season. Deeper and earlier mixing occurred during the 2010 La Niña, which subsequently delayed 2011 cool season mixing and maximum warm season surface temperatures in 2011 and 2012. Lake salinity changes are influenced by precipitation, evaporation and persistent seawater influx. The largest declines in subsurface salinity follow months after the rainy season, when temperatures cool and fresher surface water from the previous warm/wet season mixes into the subsurface. Between 2009 and 2012, more calcium carbonate precipitated during a period of higher salinity. The period of highest calcium carbonate abundance measured in sediment records that span the late nineteenth to twentieth century coincides with the failure of two consecutive rainy seasons in 1988 and 1989 as well as the coldest monthly sea surface temperature measured at Puerto Ayora in 1989. More calcium carbonate-rich laminae from AD 1550 ± 70 to 1675 ± 90 may indicate a greater frequency of prolonged droughts or cooler temperatures, although enhanced productivity may also modulate carbonate precipitation. More Ca-rich laminae in Genovesa coincide with dry conditions inferred from other Galápagos sediment proxies, as well as prolonged dry and cool conditions inferred from reconstructions of the Southern Oscillation Index and NINO3 sea surface temperatures.     

Experimental study of the effects of non-uniformly distributed fine soil on mechanical properties of Shenyang–Dandong Railway coarse-grained soil

The stress produced by repeated train loads decreases with increasing railway subgrade bed depth, and slightly weathered coarse particles of subgrade bed fillings can be broken at different levels under continuous load. Thus, the mass of fine soil, with a diameter of not more than 0.075 mm, is different at different depths. Fine soil is also sensitive to frost heave and thaw settlement. In order to study the effects of non-uniformly distributed fine soil on the mechanical properties of coarse-grained soil of the Shenyang-Dandong Railway, triaxial tests were conducted with three types of specimens, undergoing six freeze-thaw cycle numbers(0, 1, 3, 7, 9, 12) and three confining pressures(100, 200, 300 k Pa). The freezing temperature is-5 °C and the thawing temperature is +15 °C. The stress-strain behavior, static strength, resilient modulus, cohesive force and the angle of internal friction were measured for different tested specimens. As a result, the law of static strength and resilient modulus of different specimens following the increase of freeze-thaw cycles under three confining pressures is obtained. The changing law of cohesive force and friction angle of three specimens following the increase of freeze-thaw cycles is also calculated, and the different results of different specimens are also compared.     

Spatio-temporal differences in cloud cover of Landsat-8 OLI observations across China during 2013–2016

Currently, the historical archive images of Landsat family sensors are probably the most effective data products for tracking global longitudinal changes since the 1970s. However, the issue of the degree and extent of cloud coverage is always a challenge and varies distinctively worldwide. So far, acquisition probability (AP) analyses of cloud cover (CC) of Landsat observations have been conducted with different sensors at regional scale. To our knowledge, CC probability analysis for the newly-launched Landsat-8 Operational Land Imager (OLI) across China is not reported. In this paper, monthly, seasonal, and annual APs for Landsat OLI (44,228 in total) images over China acquired from April 2013 to October 2016 with various CC thresholds were analyzed. The results showed that: first, the cumulative average APs of all OLI data over China at the CC thresholds ≤30% was about 49.6% which illustrated the availability of OLI imagery across China. Second, the spatial patterns of 10%, 20%, and 30% CC thresholds of OLI observations, coincided well with the precipitation distributions separated by the respective 200 mm, 400 mm, and 800 mm isohyetal lines. Third, the APs of images with the 30% CC threshold are the highest in autumn and winter especially in October of 58.7%, while the corresponding lowest probability occurred in June of 41.0%. Finally, the spatial differences in APs of targeted images with ≤30% CC thresholds were quite significant. At regional scales, the arid and semi-arid areas, Inland River and Songliao River basins, and northwestern side of the Hu Huanyong population line had the larger probabilities of obtaining high-quality images. Our study suggested that OLI imagery satisfy the data requirements needed for land surface monitoring, although there existed obvious spatio-temporal differences in APs over China at the 30% CC threshold.     

Mean ionospheric properties in winter at Zhongshan Station,Antarctica

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Influence of the atmospheric circulation on ice-thermal processes on Baikal during 1950–2010

A study is made of the influence of the large-scale atmospheric circulation, described by the indices of Northern Hemisphere Teleconnection Patterns, on air temperature and ice-thermal characteristics of Lake Baikal for the time interval 1950–2010. Multiple linear regression equations have been obtained to account for 46–47% of the air temperature changes during the winter, spring and autumn seasons, and for 18% during the summer season. The main contribution to air temperature change for separate seasons (except in the summertime) and ice-thermal characteristics is made by the fluctuations of the AO and NAO indices characterizing the west-east transport of air masses, and of the SCAND and Sh indices of the mechanisms blocking this transport.     

Left out? Observations on the RGS-IBG conference on social exclusion and the city

Summary On 29 October 1998, the RGS-IBG invited delegates to a conference entitled 'Social exclusion and the city', with Geoff Mulgan (founder of the think-tank Demos and a policy advisor to Prime Minister Blair) as the keynote speaker. The event was well attended, providing much useful insight into the government policies of the 'Social Exclusion Unit' and ongoing academic research into the processes and problems of 'social exclusion'. Here we provide some general observations on the conference and some suggestions regarding the possible directions of the debate on social exclusion and inclusion.     

The China Society on Tibet Plateau

President:Zheng Du (Academician of CAS)Secretary-General:Dr. Zhu LipingAddress: 11A, Datun Road, Beijing 100101, ChinaE-mail: zhulp@igsnrr.ac.cn Website:www.cstp.org.cnThe China Society on Tibet Plateau (CSTP), led by the China Association of Science and Technology (CAST), is a national, scholarly and non-profit making organization consisting of scientists and technologists engaged in the research and construction of Qinghai-Tibet Plateau. It is a key social power for promo…     

Studies on frozen ground of China

1ThestatusoffrozengroundinChinaBased on previous studies, Zhou and Guo (1982) summarized the distribution characteristics of permafrost in China and indicated that the permafrost area in China is about 215×104 km2, in which about 163.4×104 km2 is on the Tibetan Plateau. After mapping and zonation of frozen ground in 1983, Xu and Wang suggested that the areas of permafrost, seasonally frozen ground and temporal frozen ground in China were 206.8×104 km2, 513.7×104 km2 and 229.1×104 km2 …     

Comments on “Automated Geography”

Mapping patterns of species richness is a longstanding tradition in biogeography and more recently in conservation planning. This paper describes the effects of sampling unit size on patterns of vertebrate richness across landscapes in the Intermountain Sagebrush and Rocky Mountain Forest ecoregions in Idaho. Variability of richness decreased with increasing size of the spatial sampling units at both sites, with greater overall variability in the forested site. Richness in the sagebrush region was best explained by alpha diversity, whereas beta diversity accounted for more of the variability in richness in the forested site.     

Territorial spatial zoning based on suitability evaluation and its impact on ecosystem services in Ezhou city

Exploring the spatial zoning of urban territories and their ecological effects under different decision preferences is an important approach to promote the sustainable utilization of regional resources. This paper constructs an index system for evaluating the suitability of territorial space development from the perspectives of urban development, agricultural production, and ecological conservation. It predicts and simulates the trade-offs between territorial space development and protection in ...     

The effects of enclosures and land-use contracts on rangeland degradation on the Qinghai–Tibetan plateau

Rangeland degradation on the Qinghai–Tibetan Plateau is a growing concern, often attributed to climate change and overgrazing. A minority of researchers have suggested instead that degradation may be caused by changes in land management, particularly enclosures and the contracting of long-term rangeland use rights to households. However, these claims have been hampered by a lack of empirical evidence. This field experiment is the first to compare rangeland conditions over time in the case of different management regimes on the Qinghai–Tibetan Plateau, specifically single-household versus multi-household management. A survey of vegetation properties in Maqu County, Gansu province in 2009, and repeated in 2011, examined the differences between single- and multi-household management in terms of vegetation biomass, cover, and species richness. In 2009, the biomass of the sedge group under multi-household management was significantly higher than that under single-household management. In 2011, biomass, vegetation cover, and species richness were all significantly higher under multi-household management than single-household management. These data suggest the flaws of the tragedy of the commons assumptions underlying single-household management.     

Spatial variability and pattern analysis of soil properties in Dehui city, Jilin province

1IntroductionSoil nutrient, as the synthetic results under the influence of various anthropogenic activities and the factors such as climate and topography, etc., possesses certain spatial distribution characteristics, and certain structural and stochastic characteristics. The study of the differences existing in different parts of the region lays the foundation for adjusting all management measures and all material input capacities and for gaining the maximal economic benefit. Presently, the …     

Commentary on Carl O. Sauer ∗

Book Reviews are in this articles.

Managing and Marketing of Urban Development and Urban Life. GERHARD O. BRAUN, ed. Berlin: Dietrich Reimer Verlag, 1994. Abhandlungen-Anthropogeographie, Bd. 52. xv and 687 pp., maps, diags., and biblio. DM 129.00 paper (ISBN 3-496-02560-3).

Evolution of Infectious Disease. PAUL W. EWALD. New York and Oxford: Oxford University Press, 1994. viii, 298 pp., diags., index, glossary, and biblio. $35.00 cloth (ISBN 0-19-506058-X).

Upstate Arcadia: Landscape, Aesthetics, and the Triumph of Social Differentiation in America. PETER J. HUGILL. Lanham, MD and London: Rowman and Littlefield, 1995. xvi and 255 pp., maps, tables, photos, biblio, and index. $61.50 cloth (ISBN 0-8476-7855-5); $24.95 paper (ISBN 0-8476-7856-3).

Urban Land Use Planning. 4th ed. EDWARD J. KAISER, DAVID R. GODSCHALK, and F. STEWART CHAPIN, JR. Urbana: University of Illinois Press, 1995. xv and 493 pp., tables, figs., and index. $40.00 cloth (ISBN 0-252-02101-0).

The Asian Pacific Rim and Globalization: Enterprise, Governance and Territoriality. RICHARD LE HERON and SAM OCK PARK, eds. Brookfield, VT: Avebury Publishing Group, 1995. xiv and 188 pp., maps, diags., and biblio. $55.95 cloth (ISBN 1-85628-894-3).

The Global Casino: An Introduction to Environmental Issues. NICK MIDDLETON. New York and London: Edward Arnold, 1995. 332 pp., maps, figs., and biblio. $26.95 paper (ISBN 0-340-59493-4).

A Geography of Pennsylvania. E. WIL-LARD MILLER, ed. University Park: Pennsylvania State University Press, 1995. xviii and 406 pp., maps, photos, tables, figs., biblio., and index. $75.00 cloth (ISBN 0-271-01017-7); $25.00 paper (ISBN 0-271-01342-7).

Mountain Environments and Geographic Information Systems. MARTIN F. PRICE and D. IAN HEYWOOD, eds. Bristol, PA, and London: Taylor &; Francis, 1994. xiv and 309 pp., figs., tables, maps, plates, biblio., and index. $95.00 cloth (ISBN 0-7484-0088-5).

Geographical Data Analysis. NIGEL WAL-FORD. New York and Chichester: John Wiley &; Sons, 1995. xi and 446 pp., apps., index, and biblio. $59.95 paper (ISBN 0-471-94162-X).     

Assessment on the sustainability of water resources utilization in Central Asia based on water resources carrying capacity

Situated in the hinterland of Eurasia, Central Asia is characterized by an arid climate and sparse rainfall. The uneven spatial distribution of water and land resources across the region has pressured economic and social development. An accurate understanding of Central Asia’s water resources carrying capacity(WRCC) is vital for enhancing the sustainability of water resources utilization and guiding regional economic and social activities. This study aims to facilitate the sustainability of wate...     

COMETT 2 Project on Chemometrics and Qualimetrics

The EEC has awarded several projects toEuropean chemometricians in its COMETTprogram.The objective of the COMETTprogram is to organize industry-orientatedtraining on a trans-national level in advancedtechnological subjects.The program is open to alltwelve EEC countries and also to the EFTAcountries (Norway,Sweden,Finland,Iceland,Austria and Switzerland).Four types of projectswere awarded,namely:(i) Creation of a network for analysingtraining needs,organizing exchanges,publicizing courses and learning material,etc.This network is called     

Human’s digital footprints on the Qinghai-Tibet Plateau: Variations during festivals and impacts on nature reserves

Mobile internet and wireless communication technologies have produced unprecedented location-aware data. Such big geospatial data can be used as a proxy measure of the ‘digital footprints' left by us on the planet and provide a valuable opportunity to understand the dynamic and short-term human disturbance on the nature at fine scales. This study investigated the spatiotemporal variations of human's digital footprints on the Qinghai-Tibet Plateau using smartphone-users-generated Tencent's location request data. The results showed that human's digital footprints cover less than 5% of Qinghai and Tibet, exhibiting either a U-shaped or an N-shaped temporal change pattern during the major festivals. Spatial changes of the digital footprints manifested a transition process from dispersion to concentration in Xining and Lhasa. Human disturbance assessment of seven large nature reserves on the plateau showed that the Qinghai Lake is the most disturbed one as shown by 14.6% of its area is stained with human digital footprints and the areal average of footprint intensity is 1.59, and the disturbance was significantly escalated during the National Day holiday. By contrast, the Qangtang and Hoh Xil are the least affected nature reserves with the two indices less than 1% and 0.1, respectively.     

Analysis on the evolution of city network based on the flow of highly cited Chinese scientists北大核心

The geographical flow of talents is affecting innovation activities worldwide, so the research on the spatial structure evolution of talent flows is particularly important. This article uses the 2014-2015 global list of highly cited scientists as raw data to retrieve the study and work experience of scientists, uses cities as the research scale, and uses the P-space model to build a highly cited Chinese scientist flow network. At the same time, uses quantile regression analyzes the impact of whether scientists in core cities are more productive. We found that: (1) The city network of highly cited Chinese scientists has the characteristics of a small-world network, and the network space structure presents a "Y-shaped" structure. China-U. S., China-Europe, and China-Australia are the main sides. (2) This article analyzes the source cities and the target cities in which scientists move, and finds that Beijing, Cambridge(UStates), Shanghai are the city with a high degree. (3) The distribution of scientists shows a trend of spreading with the development of the stage. (4) Scientists in core cities have more high-quality paper output. The increase in the degree of centrality of scientists' target cities has a greater impact on the output of scientists. © 2023 World Regional Studies.     

Studies on Yellow River Project: A Review

Although records on the Yellow River are voluminous, they are often overburdened with great engineering details and scattered in a large number of technical journals and publications as to be not readily available to geographical students.“A Symposium on the Yellow River”.