Temporal and Multidimensional Support in a GIS

Temporal and Temporal and Multidimensional Multidimensional Support in a GISSupport in a GIS

Steve KoppSteve KoppESRIESRI

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The RequirementsThe Requirements Support temporal and multidimensional Support temporal and multidimensional

data structures and file formats.data structures and file formats. Provide visualization and data Provide visualization and data

exploration tools specific to exploration tools specific to multidimensional data.multidimensional data.

Perform traditional GIS operations and Perform traditional GIS operations and analysis on multidimensional data.analysis on multidimensional data.

Build new analysis tools to take Build new analysis tools to take advantage of higher dimensionality.advantage of higher dimensionality.

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The First Step…The First Step… Extend existing functionality to Extend existing functionality to

support time and multidimensional support time and multidimensional datadata• Add support for the Add support for the netCDFnetCDF data data

formatformat• Dynamic Temporal Graphing Dynamic Temporal Graphing • Mapping change through timeMapping change through time

Support temporal animationSupport temporal animation Initial focusInitial focus

• Data access and visualizationData access and visualization• Earth science modelingEarth science modeling

Extend existing functionality to Extend existing functionality to support time and multidimensional support time and multidimensional datadata• Add support for the Add support for the netCDFnetCDF data data

formatformat• Dynamic Temporal Graphing Dynamic Temporal Graphing • Mapping change through timeMapping change through time

Support temporal animationSupport temporal animation Initial focusInitial focus

• Data access and visualizationData access and visualization• Earth science modelingEarth science modeling

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Temporal Data Structures for GISTemporal Data Structures for GIS Vector Data StructuresVector Data Structures

• Points, Lines, PolygonsPoints, Lines, Polygons• Add attributes, fields and relationships to storage Add attributes, fields and relationships to storage

and query of time.and query of time. Raster Data StructuresRaster Data Structures

• A table pointing to a collection of raster datasets A table pointing to a collection of raster datasets with a time attribute.with a time attribute.

Multidimensional ArraysMultidimensional Arrays• Already support time as a dimension Already support time as a dimension

e.g. netCDF, HDF, GRIB, etc.e.g. netCDF, HDF, GRIB, etc.

• New to most GIS users, common to Earth science New to most GIS users, common to Earth science modeling community.modeling community.

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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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NetCDF in ArcGISNetCDF in ArcGIS NetCDF data is accessed as NetCDF data is accessed as

• RasterRaster• FeatureFeature• TableTable

Direct read,Direct read,no scratch fileno scratch file

Also write GIS Also write GIS data to netCDFdata to netCDF

NetCDF data is accessed as NetCDF data is accessed as • RasterRaster• FeatureFeature• TableTable

Direct read,Direct read,no scratch fileno scratch file

Also write GIS Also write GIS data to netCDFdata to netCDF

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NetCDF ToolsNetCDF 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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Using NetCDF DataUsing NetCDF Data Behaves the same as any layer or table in:Behaves the same as any layer or table in:

• DisplayDisplay Same display tools for raster and feature layers will work Same display tools for raster and feature layers will work

on netCDF raster and netCDF feature layers.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 Multidimensional data can be animated through a

dimension (e.g. time, pressure, elevation)dimension (e.g. time, pressure, elevation)

• Analysis ToolsAnalysis Tools A netCDF raster layer will work just like any other raster A netCDF raster layer will work just like any other raster

layer, feature layer, or table. (e.g. create buffers around layer, feature layer, or table. (e.g. create buffers around netCDF points, reproject rasters, query tables, etc.)netCDF points, reproject rasters, query tables, etc.)

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Maps and Graphs from netCDFMaps and Graphs from netCDF

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Emphasis on Data ExplorationEmphasis on Data Exploration Support animation of graphs Support animation of graphs

temporally synchronized with mapstemporally synchronized with maps Support Linking and BrushingSupport Linking and Brushing

• Mechanisms used to visually explore the Mechanisms used to visually explore the connections between information in maps, connections between information in maps, graphs and tables.graphs and tables.

• Connecting multiple visualizations provides Connecting multiple visualizations provides more information than considering the more information than considering the component visualizations independently.component visualizations independently.

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Dynamic Linking Dynamic Linking between Maps, between Maps,

Graphs, and Graphs, and TablesTables

Intelligent Temporal AxesIntelligent Temporal Axes

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AnimationAnimation

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Provide Appropriate Cartography for Earth Provide Appropriate Cartography for Earth Science ModelersScience Modelers

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National Weather Service forecast for July 18th from NDFD netCDF

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Some obstacles…Some obstacles…

Date standards – not widely honoredDate standards – not widely honored Too many flavors of n-dim formatsToo many flavors of n-dim formats

• Loose standardizationLoose standardization• No ‘best practices’ guidelinesNo ‘best practices’ guidelines

Weak coordinate system handling in Weak coordinate system handling in n-dim formatsn-dim formats• Horizontal – mostly lat/long WGS84Horizontal – mostly lat/long WGS84• Other dimensions such as vertical and Other dimensions such as vertical and

time often not specified.time often not specified.