Multidimensional%20Data%20and%20GIS

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Multidimensional Data and GIS

• Steve Kopp
• Nawajish Noman
• ESRI

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Overview

• Introduction to Multidimensional Data
• What is netCDF?
• Some netCDF data sources
• Working with netCDF in ArcGIS

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Multidimensional Data

• Data cube (3D) or hypercube (4D,5D)
• Temperature varying with time
• Temperature varying with time and altitude

T
Y
X
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Gridded Data
Raster
Point Features
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Multidimensional Data
Time 3
Time 2
Time 1
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Multidimensional Data
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Multidimensional Data
Time 3
Time 2
Time 1
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Multidimensional Data
Time 1
Time 2
Data Cube
Time 3
Time Slices
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Multidimensional Data
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Multidimensional Data Formats

• NetCDF (network Common Data Form)
• HDF (4.x and previous releases), HDF-EOS, HDF5
  (Hierarchical Data Format)
• GRIB, GRIB II (GRIdded Binary)

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What is NetCDF?

• NetCDF (network Common Data Form)
• A platform independent format for representing
  multi-dimensional array-orientated scientific
  data.
• Self Describing - a netCDF file includes
  information about the data it contains.
• Direct Access - a small subset of a large dataset
  may be accessed efficiently, without first
  reading through all the preceding data.
• Sharable - one writer and multiple readers may
  simultaneously access the same netCDF file.
• NetCDF is new to the GIS community but widely
  used by scientific communities for around many
  years

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Why NetCDF?

• Most commonly used format in the oceanographic
  and atmospheric science for observational data
  and numerical modeling
• The National Center for Atmospheric Research
  (NCAR)
• University Corporation for Atmospheric Research
  (UCAR) NOAA's Climate Diagnostics Center (CDC)
• Los Alamos National Laboratory (LANL)
• The National Center for Supercomputing
  Applications
• US Air Force and Navy
• Atmospheric Research in Australia
• Australia Defense
• UK Hydrographic Office
• NATO
• ...

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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 ...

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Storing Data in a netCDF File
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Storing Data in a netCDF File
Time 1 Y 1 X 1 to 4
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Storing Data in a netCDF File
Time 1 Y 1 to 4 X 1 to 4
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Storing Data in a netCDF File
Time 1 to 3 Y 1 to 4 X 1 to 4
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NetCDF Conventions

• CF Conventions (Recommended, if applicable)
• COARDS Conventions (1995 standard that CF
  Conventions extends and generalizes)
• GDT Conventions (1999 standard that CF
  Conventions extends and generalizes)
• CDC Conventions (for gridded data, compatible
  with but more restrictive than COARDS)
• NCAR-RAF Conventions for Aircraft Data
• AMBER Trajectory Conventions for molecular
  dynamics simulations
• NUWG Conventions (1992-1995 effort to create some
  observational data conventions)
• PMEL-EPIC Conventions
• GDV Conventions (deprecated)

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CF Convention

• Climate and Forecast (CF) Convention
• http//www.unidata.ucar.edu/software/netcdf/docs/c
  onventions.html
• Initially developed for
• Climate and forecast data
• Atmosphere, surface and ocean model-generated
  data
• Comparable observational datasets
• The CF conventions generalize and extend the
  COARDS (Cooperative Ocean/Atmosphere Research
  Data Service) convention.
• CF is now the most widely used conventions for
  geospatial netCDF data. It has the best
  coordinate system handling.

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Current and Future Standards

• Fill in details
• Galeon WCS
• OGC testbed
• CF v2

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NetCDF Data Sources

• Community Climate Systems Model (CCSM) 
  http//www.ccsm.ucar.edu, https//www.earthsystemg
  rid.org/
• The CCSM is fully-coupled, global climate model
  that provides state-of-the-art computer
  simulations of the Earth's past, present, and
  future climate states.
• 100 yrs of climate change forecast data
  (2000-2099)
• Control runs (1870-1999) and scenario runs
• Temperature, precipitation flux, surface snow
  thickness, snowfall flux, cloud water content,
  etc.
• Program for Climate Model Diagnosis and
  Intercomparison (PCMDI) http//www-pcmdi.llnl.gov/

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NetCDF Data Sources

• Vegetation and Ecosystem Modeling and Analysis
  Project (VEMAP) http//dataportal.ucar.edu/vemap/m
  ain.html
• VEMAP was a large, collaborative, multi-agency
  program to simulate and understand ecosystem
  dynamics for the continental United States.
• The VEMAP Data Portal is a central collection of
  files maintained and serviced by the NCAR Data
  Group
• Climate data interval Annual, monthly, and
  daily.
• Data type Historical and model results
• Data Temperature, irradiance, precipitation,
  humidity, incident solar radiation, vapor
  pressure, elevation, land area, vegetation, water
  holding capacity of soil, etc.

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NetCDF Data Sources

• British Atmospheric Data Center (BADC)
  http//badc.nerc.ac.uk/data/
• The role of the BADC is to assist UK atmospheric
  researchers to locate, access and interpret
  atmospheric data.
• Many datasets are publicly available but datasets
  marked with key symbol have restricted access.
• Datasets are organized by projects or
  organizations.
• Climatology Interdisciplinary Data Collection
  (CIDC) has monthly means of over 70 Climate
  Parameters.
• Met Office - Historical Central England
  Temperature Data has the monthly series, which
  begins in 1659, is the longest available
  instrumental record of temperature in the world.
  The daily series begins in 1772.

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NetCDF Data Sources

• National Oceanic Atmospheric Administration
  (NOAA)
• National Digital Forecast Database (NDFD)
  http//www.nws.noaa.gov/ndfd/
• Radar Integrated Display with Geospatial Element
  (RIDGE) http//www.srh.weather.gov/ridge/
• Precipitation Analysis http//www.srh.noaa.gov/rfc
  share/precip_download.php
• Climate Diagnostics Center http//www.cdc.noaa.gov
  /

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NetCDF in ArcGIS

• NetCDF data is accessed as
• Raster
• Feature
• Table
• Direct read (no scratch file)
• Exports GIS data to netCDF

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NetCDF Tools

• Toolbox Multidimension Tools
• Make NetCDF Raster Layer
• Make NetCDF Feature Layer
• Make NetCDF Table View
• Raster to NetCDF
• Feature to NetCDF
• Table to NetCDF
• Select by Dimension

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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.
• Graphing
• Driven by the table just like any other chart.
• Animation
• Multidimensional data can be animated through a
  dimension (e.g. time, pressure, elevation)
• Analysis 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.)

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NetCDF Layer/Table Properties
Raster
Feature
Table
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Making a NetCDF Raster Layer

• Drag and drop
• Use the tool

• Usage MakeNetCDFRasterLayer ltin_netCDF_filegt
  ltvariablegt ltx_dimensiongt lty_dimensiongt
  ltout_raster_layergt band_dimension Dimension
  ValueDimension Value... BY_VALUE
  BY_INDEX

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Changing Time Slice
(Selecting a different dimension value)
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NetCDF and Spatial Reference

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