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Some spatial modelling examples for discussion

Some spatial modelling examples for discussion. Marian Scott NERC September 2010. ECCOMAGS Project. Funded by EC FPV – Nuclear Safety, Partners

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Some spatial modelling examples for discussion

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  1. Some spatial modelling examples for discussion Marian Scott NERC September 2010

  2. ECCOMAGS Project • Funded by EC FPV – Nuclear Safety, • Partners • BfS (Germany), CEA (France), DEMA/DTU (Denmark), GBA (Austria), HSK (Switzerland), IGM (Portugal), SSI (Sweden), SGU (Sweden), STUK (Finland), SURRC (UK) • Airborne Gamma-ray Spectrometry (AGS) • To assess comparability of the European AGS systems • To assess comparability of AGS with ground-based systems.

  3. Exercise Survey Areas

  4. Three spatial scales of measurement: • Ground based soil sampling • In-situ monitoring • Aerial monitoring • How comparable are the three sets of measurement? What issues do we need to consider (downscaling/upscaling)?

  5. Ground sampling locations

  6. Pre-Characterisation-sampling plan for in-situ measurement • Expanding hexagonal sampling pattern showing the radial numbers and shell designations.

  7. 137Cs Map 6th June

  8. Area X – 137Cs

  9. 137Cs regridded maps – Area Y

  10. Shape Analysis – Wigtown Merse

  11. Example: Mapping SO2 over Europe and through time How has SO2 levels changed over time as a result of international agreements? How is SO2 distributed over Europe? A spatial model (over Europe), which may change over time- a spatio-temporal model

  12. Spatial Analysis Across Time At each time point a plane across space was fitted and Gaussian Variograms of the residuals were computed. The average of the variogram parameters’ estimates were used to obtain the spatial covariance matrix .

  13. Example: River quality over a river basin How have nitrate levels changed over time as a result of changes in management and diffuse pollution control? How are nitrate levels distributed over river basin? A spatio-temporal model

  14. some comments modelling over space and time is challenging- it lies at much of the controversies we have seen about climate change predictions some simple approaches are to look at each spatial location over time, to look at each spatial pattern at each timepoint A spatio-temporal model combines these approaches and may introduce an interaction, so that the change over time is not uniform over space

  15. Example: 60Co activity in sediment of an estuary- rp.firth Suppose wanted to estimate the inventory of 60Co in the sediments of an estuary whose boundaries have been clearly defined. We know that 60Co is particle reactive and we have a map of sediment type in the estuary. How would we make use of this information?

  16. Stratified sampling chosen

  17. Example: tritium in a South Pacific atoll- rp.mururoa Suppose wanted to map the distribution of tritium inside and atoll (tritium in sea water). This will require us to collect water samples. How should we do this?

  18. Transect sampling chosen

  19. Examples to try • try the Mururoa and Rosyth examples again and look at the map that is produced and compare it with the truth- try various sampling strategies • Library(rpanel) • rp.mururoa() • rp.firth()

  20. Orthophosphate Nutrient trends across England & Wales Nonparametric trend 1970-2009 Cyclic seasonal component Can covariates such as land use, land cover and rainfall be used to describe the trends? Spatial surface Ana-Maria Magdalina, Claire Ferguson, Marian Scott, Adrian Bowman, Duncan Lee

  21. Spatial extremes in river flows in Scotland • Exploratory analysis fitting GEV to each site • study the spatial pattern in GEV parameters- an alternative to max-stable processes

  22. Summary • Spatial modelling is an important skill, since much environmental data are spatially registered • the complexities include describing the spatial correlation structure and considering if there is a temporal component how this can be modelled.

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