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Geographic data: sources and considerations

Geographic data: sources and considerations. Geographical Concepts:. Geographic coordinate system: defines locations on the earth using an angular unit of measure, a prime meridian, and a datum - datum: defines the position of the origin and the orientation of latitude and longitude lines

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Geographic data: sources and considerations

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  1. Geographic data: sources and considerations

  2. Geographical Concepts: • Geographic coordinate system: defines locations on the earth using an angular unit of measure, a prime meridian, and a datum • - datum: defines the position of the origin and the orientation of latitude and longitude lines • Map projection: mathematical transformation of the three-dimensional surface of the earth into a flat map sheet

  3. Example of interpolated surface from point data using Inverse Distance Weighting technique. Courtesy: Science Applications International Corporation Types of spatial data in GIS • Vector data: points, lines, polygons (shapefiles) • Raster data: used in ecological niche modeling for representing environmental conditions (grids) Raster obtained through interpolation Raster obtained through remote sensing

  4. Characteristics of geographic data • Quality: →Interpolated vs. remotely sensed • →Scale at which interpolation was done • Spatial resolution – has to match the scale of the questions we try to address with ENM • Temporal resolution: can represent daily, monthly, annual, or multi-annual averages • Type: categorical vs. continuous (some ecological niche modeling algorithms don't work well with categorical data)

  5. 1.Quality: interpolation WorldClim dataset: locations of climate stations with precipitation data - 47,554 stations WorldClim 1.4 Mean annual precipitation (1960-1990) IPPC climate dataset: precipitation data from 19,800 stations

  6. 2. Spatial resolution • size of the cells in the raster IPPC mean annual precipitation 0.5° resolution WorldClim mean annual precipitation 0.008° resolution Florida panhandle

  7. MODIS EVI 15-30 October MODIS EVI 30 October-15November 3. Temporal resolution • time period averaged (days, months, decades, etc)

  8. NASA/GSFC/University of Arizona

  9. Climate projections Mean maximum temperature (1960-1990) Past climate scenarios (e.g. Pleistocene) Future climate scenarios

  10. 4. Type • Categorical data – correspond to discrete fields; the values are assigned to the entire cell area and represent the category number • Continuous data – surfaces, used for natural (physical phenomena); the values are assigned to the points and represent the actual measured value Land cover 2000 Digital elevation model

  11. Points to keep in mind when selecting geographic data for ENM • Temporal and spatial resolution of geographic data has to match those of species occurrence data; also, select a spatial resolution that matches the question asked (e.g. continental spread of an invasive species, vs. predicted distribution of a local endemic species) • Categorical data doesn’t work well with some niche modeling algorithms; it is also difficult to match its temporal resolution with occurrence data • Remotely sensed data is powerful (no interpolation), but can only be used with recent, up to date, species occurrence datasets • When downloading geographic data, pay attention to projection and datum, and any metadata available; some transformations may be necessary

  12. Sources of data • Climatic (Global) data: • WorldClim current (1960-1990) climate data http://www.worldclim.org/ • IPCC current and future climate data • http://www.ipcc-data.org/obs/get_30yr_means.html • http://www.ipcc-data.org/ddc_climscen.html • Climatic Research Unit http://www.cru.uea.ac.uk/cru/data/hrg.htm • Paleoreconstructions • PMIP http://pmip.lsce.ipsl.fr/ • NOAA: http://www.ncdc.noaa.gov/paleo/

  13. Sources of data • Marine data: • NOAA World Ocean Atlas http://www.nodc.noaa.gov/OC5/indprod.html • Climate Prediction Center http://www.cpc.noaa.gov/products/predictions/30day/SSTs/sst_clim.html • Topographic and bathymetric: • USGS Hydro 1k http://edc.usgs.gov/products/elevation/gtopo30/hydro/ • NOAA ETOPO www.ngdc.noaa.gov/mgg/global/seltopo.html • Bathymetry http://ibis.grdl.noaa.gov/cgi-bin/bathy/bathD.pl

  14. Sources of data • Satellite-derived (free): • Global Vegetation Indices: • MODIS http://edcdaac.usgs.gov/dataproducts.asp • (EVI and NDVI) 2000 to present • AVHRR http://edcsns17.cr.usgs.gov/1KM/1kmhomepage.html • (NDVI): 1985 to present • Global Land Cover: • IES Global Landcover 2000 http://www-gvm.jrc.it/glc2000/ • University of Maryland (1992) http://glcf.umiacs.umd.edu/data/

  15. Other data WWF Ecoregions http://www.worldwildlife.org/science/data.cfm UNEP IUCN Protected Areas http://sea.unep-wcmc.org/wdbpa/

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