UC 2006 Tech Session 1 NetCDF in ArcGIS 9.2

UC 2006 Tech Session2 Overview 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

UC 2006 Tech Session3 Multidimensional Data Data cube (3D) or hypercube (4D,5D…) Temperature of a location varying with timeTemperature of a location varying with time Temperature at a location varying with time and altitudeTemperature at a location varying with time and altitude E.g. for every x, y, z… you can store multiple variables with multiple time stepsE.g. for every x, y, z… you can store multiple variables with multiple time steps X Y T

UC 2006 Tech Session4 Data Cube Time Slices Multidimensional Data Time = 1 Time = 2 Time = 3

UC 2006 Tech Session5 Gridded Data Regular Grid Irregular Grid (as points)

UC 2006 Tech Session6 Multidimensional Data Time = 1 Time = 2 Time = 3

UC 2006 Tech Session7 Multidimensional Data

UC 2006 Tech Session8 What is netCDF? An array based data structure for storing multidimensional data.An array based data structure for storing multidimensional data. N-dimensional coordinates systemsN-dimensional coordinates systems –X coordinate (e.g. longitude) –Y coordinate (e.g. latitude) –Z coordinate (e.g. altitude) –Time dimension –… other dimensions Variables – support for multiple variablesVariables – support for multiple variables –Temperature, humidity, pressure, salinity, etc Geometry – implicit or explicitGeometry – implicit or explicit –Regular grid (implicit) –Irregular grid –Points X Z T Y

UC 2006 Tech Session9 What is a NetCDF file? NetCDF is a binary file A NetCDF file consists of: Global Attributes: Describe the contents of the file Dimensions:Define the structure of the data (e.g Time, Depth, Latitude, Longitude) Variables:Holds the data in arrays shaped by Dimensions Variable Attributes: Describes the contents of each variable CDL (network Common Data form Language) description takes the following form netCDF name { dimensions:... variables:... data:... }

UC 2006 Tech Session10 CF Convention There are many flavors or conventions of netCDF data, ArcGIS relies on the CF Convention. Climate and Forecast (CF) Convention Initially developed for Climate and forecast dataClimate and forecast data Atmosphere, surface and ocean model-generated dataAtmosphere, surface and ocean model-generated data Also used for observational datasetsAlso used for observational datasets CF is the most widely used convention for geospatial netCDF data. It has the best coordinate system handling.CF is the most widely used convention for geospatial netCDF data. It has the best coordinate system handling.

UC 2006 Tech Session11 NetCDF Data Sources Community Climate Systems Model (CCSM) Climate Systems Model (CCSM) Program for Climate Model Diagnosis and Intercomparison (PCMDI) for Climate Model Diagnosis and Intercomparison (PCMDI) Vegetation and Ecosystem Modeling and Analysis Project (VEMAP) and Ecosystem Modeling and Analysis Project (VEMAP) British Atmospheric Data Center (BADC) Atmospheric Data Center (BADC) National Digital Forecast Database (NDFD) Digital Forecast Database (NDFD) Radar Integrated Display with Geospatial Element (RIDGE) Integrated Display with Geospatial Element (RIDGE) Precipitation Analysis Analysis Climate Diagnostics Center Diagnostics Center

UC 2006 Tech Session12 NetCDF in ArcGIS NetCDF data is accessed asNetCDF data is accessed as Raster Raster Feature Feature Table Table Direct readDirect read Exports GIS data to netCDFExports GIS data to netCDF

UC 2006 Tech Session13 NetCDF Tools Toolbox: Multidimension Tools Make NetCDF Raster Layer Make NetCDF Raster Layer Make NetCDF Feature Layer Make NetCDF Feature Layer Make NetCDF Table View Make NetCDF Table View Raster to NetCDF Raster to NetCDF Feature to NetCDF Feature to NetCDF Table to NetCDF Table to NetCDF Select by Dimension Select by Dimension

UC 2006 Tech Session14 NetCDF Layer/Table Properties RasterRaster FeatureFeature TableTable

UC 2006 Tech Session15 Using NetCDF Data Behaves the same as any layer or table Display Same display tools for raster and feature layers will work on netCDF raster and netCDF feature layers. Same display tools for raster and feature layers will work on 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. time, pressure, elevation) Multidimensional data can be animated through a dimension (e.g. time, pressure, elevation) Analysis ToolsAnalysis Tools A netCDF layer or table will work just like any other raster layer, feature layer, or table. (e.g. create buffers around netCDF points, reproject rasters, query tables, etc.) A netCDF layer or table will work just like any other raster layer, feature layer, or table. (e.g. create buffers around netCDF points, reproject rasters, query tables, etc.)

UC 2006 Tech Session16 NetCDF and Coordinate Systems Geographic Coordinate Systems (GCS)Geographic Coordinate Systems (GCS) X dimension units: degrees_east X dimension units: degrees_east Y dimension units: degrees_north Y dimension units: degrees_north Projected Coordinate Systems (PCS)Projected Coordinate Systems (PCS) X dimension standard_name: projection_x_coordinate X dimension standard_name: projection_x_coordinate Y dimension standard_name: projection_y_coordinate Y dimension standard_name: projection_y_coordinate Variable has a grid_mapping attribute. Variable has a grid_mapping attribute. CF conventions currently supports only eight predefined coordinate systems CF conventions currently supports only eight predefined coordinate systems UndefinedUndefined If not GCS or PCS If not GCS or PCS ArcGIS writes (and recognizes) PE String as a variable attribute. ArcGIS writes (and recognizes) PE String as a variable attribute.

UC 2006 Tech Session17 Emerging Standards CF Version 2CF Version 2 The next generation of the Climate and Forecast convention of netCDF, just beginning.The next generation of the Climate and Forecast convention of netCDF, just beginning. GALEONGALEON OGC testbed project to evaluate netCDF suitability as a WCS well known binary.OGC testbed project to evaluate netCDF suitability as a WCS well known binary. Common Data Model (CDM)Common Data Model (CDM) A new API to access netCDF, HDF, GRIB, and OpenDAP through a single API.A new API to access netCDF, HDF, GRIB, and OpenDAP through a single API. NcMLNcML NetCDF Markup Language, like GML for netCDF earth science dataNetCDF Markup Language, like GML for netCDF earth science data