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Interactive visualization applied to multivariate geochemical data: A case study
KTH, Superseded Departments, Land and Water Resources Engineering.
2003 (English)In: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 107, 577-580 p.Article in journal (Refereed) Published
Abstract [en]

Geochemical survey data have commonly been analysed combining methods from several disciplines - statistics, geostatistics, geographic information technology, visualization. In initial stages of analysis, tables are often used to describe the data and present statistical measures. For too often the original data are manipulated in one or another way, for example, using mathematical transformations, or interpolation of points to a surface. It is the author's opinion that raw geochemical data should be used in initial stages of data description, thus preserving the original details. This is not a simple task, as geochemical data are commonly complex, multivariate, and collected on irregular grid. Data contain outliers, element contents vary within thousands of ppm (parts per million), and different chemical elements may be correlated. In the present study a graphical approach has been used to study distribution of 5 heavy metals in glacial till. Using interactive visualization and multiple linked views of the data, the following issues were addressed: multi-element outliers, spatial trends, multi-element correlations and patterns. Interactive graphical techniques proved to be especially suitable for studying outliers and identifying and locating samples that are redundant and may be removed from data without loss of information. Visualization using linked views gave valuable insights about metal correlations and spatial trends. As the development of appropriate tools for analysing multivariate spatial data are still in its early stages, visualization freeware seems to be a good alternative providing powerful, easy to use and intuitive techniques for exploratory data analysis.

Place, publisher, year, edition, pages
2003. Vol. 107, 577-580 p.
Keyword [en]
Engineering research, Environmental engineering, Environmental impact, Geographic information systems, Graph theory, Heavy metals, Interactive computer systems, Interpolation, Mathematical transformations, Statistical methods, Surveys
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-5027DOI: 10.1051/jp4:20030369ISI: 000183782300142OAI: oai:DiVA.org:kth-5027DiVA: diva2:7634
Note
QC 20100609Available from: 2005-04-18 Created: 2005-04-18 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Visualization, integration and analysis of multi-element geochemical data
Open this publication in new window or tab >>Visualization, integration and analysis of multi-element geochemical data
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

generated large databases containing information on the concentrations of chemical elements in rocks, surface sediments and biogeochemical materials. Regional geochemical data being imprecise, multivariate, spatially auto-correlated and non-normally distributed pose specific problems to the choice of data analysis methods. Commonly several methods are combined, and the choice of techniques depends on the characteristics of data as well as the purpose of study. One critical issue is dealing with extreme data values (or outliers) in the initial stages of analysis. Another common problem is that integrated analysis of several geochemical datasets is not possible without interpolating the point data into surfaces. Finally, separation of anthropogenic influences from natural geochemical background in the surface materials is an issue of great importance for environmental studies.

This study describes an approach to address the above-mentioned problems by a flexible combination and use of GIS and multivariate statistical techniques with high-dimensional visualization. Dynamically linked parallel coordinate and scatterplot matrix display techniques allow simultaneous presentation of spatial, multi-element and qualitative information components of geochemical data. The plots not only display data in multi-dimensional space, but also allow detailed inspection of the data with interactive multi-dimensional brushing tools. The results of the study indicate that these simple high-dimensional visualization techniques can successfully complement the traditional statistical and GIS analysis in all steps of data processing, from data description and outlier identification through data integration, analysis, validation, and presentation of results. The outcomes of the study include: a visual procedure towards intelligent data cleaning where potentially significant information in very high element concentrations is preserved, methods for integration and visual analysis of geochemical datasets collected in different grids, estimation of geochemical baseline concentrations of trace metals in till geochemistry of southeastern Sweden, use of multi-element spatial fingerprints to trace natural geochemical patterns in biogeochemistry, and a new graphical approach to present multi-element geochemical data summaries and results from numerical analysis.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1018
Keyword
Earth sciences, GIS, interactive visualization, glacial till, biogeochemistry, metals, southeastern Sweden, Geovetenskap
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-169 (URN)91-7178-014-9 (ISBN)
Public defence
2005-04-21, Kollegiesalen, Valhallavägen 79, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100609Available from: 2005-04-18 Created: 2005-04-18 Last updated: 2010-06-09Bibliographically approved

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