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Sampling and Kriging Spatial Means: Efficiency and Conditions  [PDF]
Jin-Feng Wang,Lian-Fa Li,George Christakos
Sensors , 2009, DOI: 10.3390/s90705224
Abstract: Sampling and estimation of geographical attributes that vary across space (e.g., area temperature, urban pollution level, provincial cultivated land, regional population mortality and state agricultural production) are common yet important constituents of many real-world applications. Spatial attribute estimation and the associated accuracy depend on the available sampling design and statistical inference modelling. In the present work, our concern is areal attribute estimation, in which the spatial sampling and Kriging means are compared in terms of mean values, variances of mean values, comparative efficiencies and underlying conditions. Both the theoretical analysis and the empirical study show that the mean Kriging technique outperforms other commonly-used techniques. Estimation techniques that account for spatial correlation (dependence) are more efficient than those that do not, whereas the comparative efficiencies of the various methods change with surface features. The mean Kriging technique can be applied to other spatially distributed attributes, as well.
Sampling methods in environmental spatial analysys and their effects on spatial continuity display
环境空间分析中常用采样方法及其对空间结构表达的影响

QI Feng,WANG Xuejun,
齐峰
,王学军

环境科学学报 , 2000,
Abstract: Spatial structure analysis in describing the spatial continuity of regionalized variables is a fundamental component in spatial analysis. Effects of different sampling design parameters on the quality of estimates from spatially correlated data have been extensively investigated, while efficiency of sampling designs for displaying and describing spatial continuity, particularly in environmental research, has been given less attention. In this paper, the performances of several sampling designs were examined and their different effects on simulated data were compared. Sample variogram is used to describe spatial structure. Based mainly on visual comparison, results showed that both sample size and sample pattern are of significant influence on the sample variograms, therefore, each plays important role on practical sampling.
Str ata Efficiency and Optimization str ategy of Str atified Sampling on Spatial Population
地理空间中不同分层抽样方式的分层效率 与优化策略

CAO Zhidong,WANG Jinfeng,LI Lianfa,JIANG Chengsheng,
曹志冬
,王劲峰,李连发,姜成晟

地理科学进展 , 2008,
Abstract: Efficiency of stratified sampling for geospatial population is restricted by spatial auto-correlation. Strata efficiency origins from two aspects: the first is spatial auto-correlation, which makes sampling with dispersed distribution improve the accuracy; and the second is priori knowledge, which can make the variance smaller within strata than within the overall population. The strata efficiency for knowledge strata is more outstanding than that of arbitrary strata only in the geographical object with strong spatial auto-correlation; when the spatial auto-correlation is weak, knowledge will not be preferred to the arbitrary strata. Spatial auto-correlation has an important influence on stratified sampling design: Although a stratified statostoc always "gains" in terms of accuracy, the implementation of the technique is conditional, expensive and sometime unnecessary. This is often overlooked in practical application. Different stratified sampling surveys for the ratio of thin-non-cultivated component in Shandong Province are simulated by using Mento Carlo method. Simulated results validate the influence of spatial: auto-correlation on different stratified methods. Finally, this paper proposes optimization strategy of strata selection for geospatial objects.
Generalized Spatial Two Stage Least Squares Estimation of Spatial Autoregressive Models with Autoregressive Disturbances in the Presence of Endogenous Regressors and Many Instruments  [PDF]
Fei Jin,Lung-fei Lee
Econometrics , 2013, DOI: 10.3390/econometrics1010071
Abstract: This paper studies the generalized spatial two stage least squares (GS2SLS) estimation of spatial autoregressive models with autoregressive disturbances when there are endogenous regressors with many valid instruments. Using many instruments may improve the efficiency of estimators asymptotically, but the bias might be large in finite samples, making the inference inaccurate. We consider the case that the number of instruments K increases with, but at a rate slower than, the sample size, and derive the approximate mean square errors (MSE) that account for the trade-offs between the bias and variance, for both the GS2SLS estimator and a bias-corrected GS2SLS estimator. A criterion function for the optimal K selection can be based on the approximate MSEs. Monte Carlo experiments are provided to show the performance of our procedure of choosing K.
The Efficiency of Variance Reduction in Manufacturing and Service Systems: The Comparison of the Control Variates and Stratified Sampling
Ergün Eraslan,Berna Dengiz
Mathematical Problems in Engineering , 2009, DOI: 10.1155/2009/791750
Abstract: There has been a great interest in the use of variance reduction techniques (VRTs) in simulation output analysis for the purpose of improving accuracy when the performance measurements of complex production and service systems are estimated. Therefore, a simulation output analysis to improve the accuracy and reliability of the output is required. The performance measurements are required to have a narrow and strong confidence interval. For a given confidence level, a smaller confidence interval is supposed to be better than the larger one. The wide of confidence interval, determined by the half length, will depend on the variance. Generally, increased replication of the simulation model appears to have been the easiest way to reduce variance but this increases the simulation costs in complex-structured and large-sized manufacturing and service systems. Thus, VRTs are used in experiments to avoid computational cost of decision-making processes for more precise results. In this study, the effect of Control Variates (CVs) and Stratified Sampling (SS) techniques in reducing variance of the performance measurements of M/M/1 and GI/G/1 queue models is investigated considering four probability distributions utilizing randomly generated parameters for arrival and service processes.
Comparison of the efficiency of flight-interception trap models for sampling Hymenoptera and other insects
Campos, Wellington G.;Pereira, Débora B.S.;Schoereder, José H.;
Anais da Sociedade Entomológica do Brasil , 2000, DOI: 10.1590/S0301-80592000000300001
Abstract: models of insect flight traps designed by townes (1972) and masner & goulet (1981) were modified. the original and the modified models were compared in their effectiveness in sampling orders of insecta and families of hymenoptera. the use of yellow painted trays strongly improved the effectiveness of the trap proposed by masner & goulet (1981). joining in a same trap a yellow tray, typical of masner & goulet models, with a pot, typical of malaise traps, did not reduce the individual effectiveness of each system. the association of such flight interception trap models, added to the attractiveness of the yellow color allowed the operation, at the same time and place, of the three techniques that have usually been employed apart. the result was the summation of standardized samples, without loss of individual effectiveness. a smaller human effort was demanded, because the maintenance and the handling of a larger number of traps were reduced. the financial cost was also smaller, considering the fabric economy. this associated model is indicated for large faunistic surveys because one technique compensates the lower effectiveness of the other in catching some taxa.
Comparison of the Efficiency of the Various Algorithms in Stratified Sampling when the Initial Solutions are Determined with Geometric Method
International Journal of Statistics and Applications , 2012, DOI: 10.5923/j.statistics.20120201.01
Abstract: The main aim of this paper is to examine the efficiency of Genetic Algorithm (GA) of Keskintürk and Er (2007)[1], Kozak’s (2004) Random Search[2] and Lavallée and Hidiroglou’s (1988) Iterative Algorithm method[3] on determination of the stratum boundaries that minimize the variance of the estimate. Initial starting boundaries of the mentioned algorithms are obtained randomly. Here, it is aimed to reach better results in a shorter period of time by utilizing the initial boundaries obtained from Gunning and Horgan’s (2004) geometric method[4] compared to the random initial boundaries. Three algorithms are applied on various populations with both random and geometric initial boundaries and their performances are compared. With the stratification of 11 heterogenous populations that have different properties, higher variance of the estimates or infeasible solutions can be observed once the initial boundaries are obtained with geometric method.
A New Sampling Design for a Spatial Population: Path Sampling  [PDF]
Mena Patummasut,Arthur L. Dryver
Journal of Applied Sciences , 2012,
Abstract: This study proposed a new cost-effective and convenient sampling design for a spatial population, called “path sampling” and which offers the ability to sample all of the units in the researcher’s path traversed during the sampling. Path sampling is a design in which the researcher selects a path or paths from start to finish, as opposed to selecting units. Path sampling offers unbiased estimators for both mean and variance. This paper covers the pros and cons of path sampling in comparison to simple random sampling and cluster sampling.
Spatial Outlier Model and Detection Algorithm with Leapingly Sampling
空间离群点的模型与跳跃取样查找算法

HUANG Tian-qiang,QIN Xiao-lin,WANG Qin-min,
黄添强
,秦小麟,王钦敏

中国图象图形学报 , 2006,
Abstract: Existing work in outlier detection emphasizes the deviation of non-spatial attribute not only in outlier detecting in statistical database but also in spatial outlier detecting in spatial database.However,both spatial and non-spatial attributes must be synthetically considered in many applications,such as image processing,position-based service.We defined outlier in respect of taking account of both spatial and non-spatial attributes and proposed a new density-based spatial outlier detecting approach with leapingly sampling(DBSODLS).Existing density-based outlier detection approaches must calculate neighborhoods of every object,which are time-consuming.This method makes the best of neighbor information that have been detected,leapingly selects the next object, but not every object,which reduces many neighborhood queries.Theoretical comparison shows this method is better than other density-based methods in efficiency,and the experimental results also show that the approach outperforms the existing density-based methods in efficiency.
Orchid bees (Hymenoptera: Apidae) in the coastal forests of southern Brazil: diversity, efficiency of sampling methods and comparison with other Atlantic forest surveys
Mattozo, Vanessa C.;Faria, Luiz R.R.;Melo, Gabriel A.R.;
Papéis Avulsos de Zoologia (S?o Paulo) , 2011, DOI: 10.1590/S0031-10492011003300001
Abstract: surveys of orchid bees at the brazilian atlantic forest have been restricted to a few regions, making difficult to understand latitudinal patterns of distribution and diversity of these bees. for this reason we sampled the euglossine fauna at atlantic forest areas at the coastal region of s?o paulo (sete barras, faz. morro do capim: sp3) and state of paraná (antonina, reserva natural do rio cachoeira: pr3), in southern brazil. in pr3, we also evaluated the efficiency of collecting methods for sampling the fauna, comparing bait traps with direct collecting using entomological nets on fragrance baits. the diversity and abundance of bees was very low: we caught only 39 males of eight species in sp3 (euglossa iopoecila, euglossa roderici, eulaema nigrita, euglossa annectans, eulaema cingulata, euglossa pleosticta, euglossa viridis and exaerete smaragdina) and 254 males of six species in pr3 (euglossa iopoecila, euglossa annectans, euglossa stellfeldi, euglossa roderici, euglossa pleosticta and eulaema nigrita). comparing the sampling methodologies, use of insect nets on fragrance baits (six species; 221 specimens) was more efficient than bait traps (three species; 33 specimens). when comparing the faunas of these two areas with other surveys at the atlantic forest sites, through a dca analysis, we found that the two surveys presented in this paper were placed relatively close to each other, but apart from the other sites analyzed, not clustering with the southernmost survey at the subtropical atlantic forest of rio grande do sul or with the remaining surveys carried out at northern lowland sites of this biome.
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