Temporal and
Multidimensional
Support in a GIS
Steve Kopp
ESRI
The Requirements




Support temporal and
multidimensional data structures and
file formats.
Provide visualization and data
exploration tools specific to
multidimensional data.
Perform traditional GIS operations
and analysis on multidimensional
data.
Build new analysis tools to take
advantage of higher dimensionality.
1
The First Step…

Extend existing functionality to
support time and multidimensional
data
• Add support for the netCDF data
format
• Dynamic Temporal Graphing
• Mapping change through time


Support temporal animation
Initial focus
• Data access and visualization
• Earth science modeling
2
Temporal Data Structures for GIS

Vector Data Structures
• Points, Lines, Polygons
• Add attributes, fields and relationships to
storage and query of time.

Raster Data Structures
• A table pointing to a collection of raster
datasets with a time attribute.

Multidimensional Arrays
• Already support time as a dimension

e.g. netCDF, HDF, GRIB, etc.
• New to most GIS users, common to Earth
science modeling community.
3
What is netCDF?


An array based data structure for storing
multidimensional data.
N-dimensional coordinates systems
•
•
•
•
•

X coordinate (e.g. longitude)
Y coordinate (e.g. latitude)
Z coordinate (e.g. altitude)
Time dimension
… other dimensions
T
Y
Z
X
Variables – support for multiple variables
• Temperature, humidity, pressure, salinity, etc

Geometry – implicit or explicit
• Regular grid (implicit)
• Irregular grid
• Points
4
NetCDF in ArcGIS

NetCDF data is accessed as
• Raster
• Feature
• Table


Direct read,
no scratch file
Also write GIS
data to netCDF
5
NetCDF 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
6
Using NetCDF Data

Behaves the same as any layer or table in:
• 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 raster layer will work just like any other raster
layer, feature layer, or table. (e.g. create buffers around
netCDF points, reproject rasters, query tables, etc.)
7
Maps and Graphs from netCDF
8
Emphasis on Data Exploration


Support animation of graphs
temporally synchronized with maps
Support Linking and Brushing
• Mechanisms used to visually explore the
connections between information in maps,
graphs and tables.
• Connecting multiple visualizations provides
more information than considering the
component visualizations independently.
9
Dynamic Linking
between Maps,
Graphs, and
Tables
10
Intelligent Temporal Axes
Animation
12
Provide Appropriate Cartography for Earth
Science Modelers
13
National Weather Service forecast for July 18th from NDFD netCDF
14
Some obstacles…


Date standards – not widely honored
Too many flavors of n-dim formats
• Loose standardization
• No ‘best practices’ guidelines

Weak coordinate system handling in
n-dim formats
• Horizontal – mostly lat/long WGS84
• Other dimensions such as vertical and
time often not specified.
15