SPA Theory

Sampling technology is a common way to estimate characteristics of the whole population with the collected elements. However, in some cases for various reasons several samples are not possible, only one sample could be available. The model SPA (Single Point Areal Estimation) can establish relationship between the observation of single station and the observations of other kinds of stations, then project the single station observation into an areal average using correlations between all stations. For example, in Beijing PM10 is a mandatory reported air quality index, which is published at 18 official PM10 surveillance stations. Meanwhile the U.S. embassy has made hourly report of SPA PM2.5 since spring 2008, the only one PM2.5 monitoring report throughout the whole city. This novel model projects the daily PM2.5 observed at the single (US Embassy) station over the entire city to work out the city’s daily average PM2.5 concentration, using the association between that station observation and 18 official PM10 stations.  


Software Function:

(1) Data input area

Input the sample data and reference data, click “Run” button to execute the model and export the result in CSV format.

(2) Result output area

The result is presented within a table, including Date, Estimation, the model weight parameter w0, the standard deviation STDEV, and the one standard variance interval CI1, CI2.



Case study ...

Download the software:

   (1) R version (no GUI). or

   (2) GUI version (the R code is wrapped, Microsoft Windows only, 32bit).


Citation: Wang JF, Hu MG, Xu CD, Christakos G, Zhao Y. 2012. Estimation of citywide air pollution in Beijing. PLoS ONE 8(1): e53400. doi:10.1371/journal.pone.0053400


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