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UC 2006 Tech Session UC 2006 Tech Session 1 NetCDF in ArcGIS 9.2 NetCDF in ArcGIS 9.2
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UC 2006 Tech SessionUC 2006 Tech Session11
NetCDF in ArcGIS 9.2NetCDF in ArcGIS 9.2
UC 2006 Tech SessionUC 2006 Tech Session22
OverviewOverview
• Introduction to Multidimensional DataIntroduction to Multidimensional Data• What is netCDF?What is netCDF?• Some netCDF data sourcesSome netCDF data sources• Working with netCDF in ArcGISWorking with netCDF in ArcGIS
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Multidimensional DataMultidimensional Data
Data cube (3D) or hypercube (4D,5D…)Data cube (3D) or hypercube (4D,5D…)
• Temperature of a location Temperature of a location varying with timevarying with time
• Temperature at a locationTemperature at a locationvarying with time and altitudevarying with time and altitude
• E.g. for every x, y, z… you can E.g. for every x, y, z… you can store multiple variables with store multiple variables with multiple time stepsmultiple time steps
XY
TZXY
T
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Data Cube
Time Slices
Multidimensional DataMultidimensional Data
141 241 341
131 231 331
121 221 321
111 211 311
441
431
421
411Y
X
Time142 242 342
132 232 332
122 222 322
112 212 312
442
432
422
412
143 243 343
133 233 333
123 223 323
113 213 313
443
433
423
413
Time = 1
Time = 2
Time = 3
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Gridded DataGridded Data
Regular Grid
Irregular Grid(as points)(as points)
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Multidimensional DataMultidimensional Data
Time = 1
Time = 2
Time = 3
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Multidimensional DataMultidimensional Data
141 241 341
131 231 331
121 221 321
111 211 311
441
431
421
411
142 242 342
132 232 332
122 222 322
112 212 312
442
432
422
412
143 243 343
133 233 333
123 223 323
113 213 313
443
433
423
413
Y
X
TimeAltitude
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What is netCDF?What is netCDF?
• An array based data structure for storing An array based data structure for storing multidimensional data.multidimensional data.
• N-dimensional coordinates systemsN-dimensional coordinates systems– X coordinate (e.g. longitude)X coordinate (e.g. longitude)– Y coordinate (e.g. latitude)Y coordinate (e.g. latitude)– Z coordinate (e.g. altitude)Z coordinate (e.g. altitude)– Time dimensionTime dimension– … … other dimensionsother dimensions
• Variables – support for multiple variablesVariables – support for multiple variables– Temperature, humidity, pressure, salinity, etcTemperature, humidity, pressure, salinity, etc
• Geometry – implicit or explicitGeometry – implicit or explicit– Regular grid (implicit)Regular grid (implicit)– Irregular gridIrregular grid– PointsPoints
XX
ZZ
TT
YY
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What is a NetCDF file?What is a NetCDF file?
NetCDF is a binary fileNetCDF is a binary file
A NetCDF file consists of:A NetCDF file consists of:Global Attributes:Global Attributes: Describe the contents of the fileDescribe the contents of the fileDimensions:Dimensions: Define the structure of the data Define the structure of the data
(e.g Time, Depth, Latitude, Longitude)(e.g Time, Depth, Latitude, Longitude)Variables:Variables: Holds the data in arrays shaped Holds the data in arrays shaped
by Dimensionsby DimensionsVariable Attributes:Variable Attributes: Describes the contents of Describes the contents of
each variableeach variableCDL (network CDL (network CCommon ommon DData form ata form LLanguage) description takes the anguage) description takes the
following formfollowing formnetCDF name { netCDF name {
dimensions: ... dimensions: ... variables: ... variables: ... data: ... data: ...
} }
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CF ConventionCF Convention
There are many flavors or conventions of netCDF There are many flavors or conventions of netCDF data, ArcGIS relies on the CF Convention.data, ArcGIS relies on the CF Convention.
CClimate and limate and FForecast (CF) Conventionorecast (CF) Conventionhttp://www.unidata.ucar.edu/software/netcdf/docs/conventions.htmlhttp://www.unidata.ucar.edu/software/netcdf/docs/conventions.html
Initially developed forInitially developed for•Climate and forecast dataClimate and forecast data•Atmosphere, surface and ocean model-generated Atmosphere, surface and ocean model-generated
datadata•Also used for observational datasetsAlso used for observational datasets•CFCF is the most widely used convention for is the most widely used convention for
geospatial netCDF data. It has the best coordinate geospatial netCDF data. It has the best coordinate system handling.system handling.
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NetCDF Data SourcesNetCDF Data Sources
• Community Climate Systems Model (CCSM) Community Climate Systems Model (CCSM) http://www.ccsm.ucar.edu, https://www.earthsystemgrid.org/http://www.ccsm.ucar.edu, https://www.earthsystemgrid.org/
• Program for Climate Model Diagnosis and Intercomparison (PCMDI) Program for Climate Model Diagnosis and Intercomparison (PCMDI) http://www-pcmdi.llnl.gov/http://www-pcmdi.llnl.gov/
• Vegetation and Ecosystem Modeling and Analysis Project (VEMAP) Vegetation and Ecosystem Modeling and Analysis Project (VEMAP) http://dataportal.ucar.edu/vemap/main.htmlhttp://dataportal.ucar.edu/vemap/main.html
• British Atmospheric Data Center (BADC) British Atmospheric Data Center (BADC) http://badc.nerc.ac.uk/data/http://badc.nerc.ac.uk/data/
• National Digital Forecast Database (NDFD) National Digital Forecast Database (NDFD) http://www.nws.noaa.gov/ndfd/http://www.nws.noaa.gov/ndfd/
• Radar Integrated Display with Geospatial Element (RIDGE) Radar Integrated Display with Geospatial Element (RIDGE) http://www.srh.weather.gov/ridge/http://www.srh.weather.gov/ridge/
• Precipitation Analysis http://www.srh.noaa.gov/rfcshare/precip_download.phpPrecipitation Analysis http://www.srh.noaa.gov/rfcshare/precip_download.php• Climate Diagnostics Center Climate Diagnostics Center
http://www.cdc.noaa.gov/http://www.cdc.noaa.gov/
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NetCDF in ArcGISNetCDF in ArcGIS
• NetCDF data is accessed asNetCDF data is accessed as• RasterRaster• FeatureFeature• TableTable
• Direct readDirect read• Exports GIS data to netCDFExports GIS data to netCDF
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NetCDF ToolsNetCDF Tools
Toolbox: Multidimension ToolsToolbox: Multidimension Tools• Make NetCDF Raster LayerMake NetCDF Raster Layer• Make NetCDF Feature LayerMake NetCDF Feature Layer• Make NetCDF Table ViewMake NetCDF Table View• Raster to NetCDFRaster to NetCDF• Feature to NetCDFFeature to NetCDF• Table to NetCDFTable to NetCDF• Select by DimensionSelect by Dimension
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NetCDF Layer/Table PropertiesNetCDF Layer/Table Properties
RasterRaster
FeatureFeature
TableTable
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Using NetCDF DataUsing NetCDF Data
Behaves the same as any layer or table Behaves the same as any layer or table DisplayDisplay• Same display tools for raster and feature layers will work on Same display tools for raster and feature layers will work on
netCDF raster and netCDF feature layers.netCDF raster and netCDF feature layers.
• GraphingGraphing• Driven by the table just like any other chart.Driven by the table just like any other chart.
• AnimationAnimation• Multidimensional data can be animated through a dimension (e.g. Multidimensional data can be animated through a dimension (e.g.
time, pressure, elevation)time, pressure, elevation)
• Analysis ToolsAnalysis Tools• A netCDF layer or table will work just like any other raster layer, A netCDF layer or table will work just like any other raster layer,
feature layer, or table. (e.g. create buffers around netCDF points, feature layer, or table. (e.g. create buffers around netCDF points, reproject rasters, query tables, etc.)reproject rasters, query tables, etc.)
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NetCDF and Coordinate SystemsNetCDF and Coordinate Systems
• Geographic Coordinate Systems (GCS)Geographic Coordinate Systems (GCS)• X dimension units: X dimension units: degrees_eastdegrees_east• Y dimension units: Y dimension units: degrees_northdegrees_north
• Projected Coordinate Systems (PCS)Projected Coordinate Systems (PCS)• X dimension standard_name: X dimension standard_name: projection_x_coordinateprojection_x_coordinate• Y dimension standard_name: Y dimension standard_name: projection_y_coordinateprojection_y_coordinate• Variable has a Variable has a grid_mappinggrid_mapping attribute. attribute. • CF conventions currently supports only eight predefined CF conventions currently supports only eight predefined
coordinate systems coordinate systems
• UndefinedUndefined• If not GCS or PCSIf not GCS or PCS• ArcGIS writes (and recognizes) PE String as a variable attribute.ArcGIS writes (and recognizes) PE String as a variable attribute.
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Emerging StandardsEmerging Standards
• CF Version 2CF Version 2• The next generation of the Climate and Forecast convention of The next generation of the Climate and Forecast convention of
netCDF, just beginning.netCDF, just beginning.
• GALEONGALEON• OGC testbed project to evaluate netCDF suitability as a WCS well OGC testbed project to evaluate netCDF suitability as a WCS well
known binary.known binary.
• Common Data Model (CDM)Common Data Model (CDM)• A new API to access netCDF, HDF, GRIB, and OpenDAP through A new API to access netCDF, HDF, GRIB, and OpenDAP through
a single API.a single API.
• NcMLNcML• NetCDF Markup Language, like GML for netCDF earth science NetCDF Markup Language, like GML for netCDF earth science
datadata
