Outlier detection with partial information: Application to emergency mapping

Davide D'Alimonte*, Dan Cornford

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This paper, addresses the problem of novelty detection in the case that the observed data is a mixture of a known 'background' process contaminated with an unknown other process, which generates the outliers, or novel observations. The framework we describe here is quite general, employing univariate classification with incomplete information, based on knowledge of the distribution (the 'probability density function', 'pdf') of the data generated by the 'background' process. The relative proportion of this 'background' component (the 'prior' 'background' 'probability), the 'pdf' and the 'prior' probabilities of all other components are all assumed unknown. The main contribution is a new classification scheme that identifies the maximum proportion of observed data following the known 'background' distribution. The method exploits the Kolmogorov-Smirnov test to estimate the proportions, and afterwards data are Bayes optimally separated. Results, demonstrated with synthetic data, show that this approach can produce more reliable results than a standard novelty detection scheme. The classification algorithm is then applied to the problem of identifying outliers in the SIC2004 data set, in order to detect the radioactive release simulated in the 'oker' data set. We propose this method as a reliable means of novelty detection in the emergency situation which can also be used to identify outliers prior to the application of a more general automatic mapping algorithm. © Springer-Verlag 2007.

Original languageEnglish
Pages (from-to)613-620
Number of pages8
JournalStochastic environmental research and risk assessment
Issue number5
Early online date30 Jun 2007
Publication statusPublished - Aug 2008

Bibliographical note

The original publication is available at www.springerlink.com


  • novelty detection
  • known background proces
  • contamination
  • unknown process
  • outliers
  • novel observations
  • knowledge of the distribution
  • probability density function
  • pdf
  • prior ‘background’ probability
  • prior probabilities
  • Kolmogorov–Smirnov test
  • proportions
  • afterwards data
  • Bayes optimally separated
  • classification algorithm
  • SIC2004 data set
  • detection
  • radioactive release
  • ‘joker’ data set
  • emergency situation
  • automatic mapping algorithm


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