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Overview of the Godiva2 environmental data online visualization system.
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GWS Workshop, Nottingham, June 16 2008 © University of Reading 2008www.reading.ac.uk
Interactive visualization of four-dimensional environmental data using an enhanced Web Map ServiceJon Blower,Reading e-Science Centre,Environmental Systems Science Centre, University of [email protected]://www. reading.ac.uk/godiva2
2Interactive visualization of 4D environmental data
Issues we will cover
• Why does environmental science need geospatial web services?
• Online visualization of scientific data using a Web Map Service– What is meant by an “enhanced” WMS?
• Difficulties applying geospatial web services to scientific data
• Ideas for future research
3Interactive visualization of 4D environmental data
Flood prediction
We need to see into the future
Search and rescue
Climate prediction
All require interdisciplinary science!
4Interactive visualization of 4D environmental data
How can we make useful predictions?
• Need computer models that:– encapsulate our scientific knowledge– are validated by observations
• Output from these models needs to be disseminated:– within the scientific community– to government policy makers– to emergency response situations– ... often in (near) real time
• Need to compare models with other geospatial data sources– e.g. land use maps, locations of assets– Requires interoperability
5Interactive visualization of 4D environmental data
The importance of visualization
• Detecting features in models (e.g. storms)
• Diagnosing problems in models
• Preview data before downloading
• Make sense of large datasets
• Puts data into wider context
• Communicate complex concepts
6Interactive visualization of 4D environmental data
Existing scientific visualization software
• Problem-solving environments– Matlab, IDL
• 3-D desktop visualization– MayaVi
• 3-D remote visualization– Silicon Graphics
• Web-based– Live Access Server
• Geographic Information Systems (GIS)
• All require expert knowledge• Limited interoperability
between systems
7Interactive visualization of 4D environmental data
Barriers to effective visualization
• Computer model outputs are large...– Four-dimensional rasters (x,y,z,t)– High-resolution– Many variables– Ensembles– Tera/petabyte scale
• ... complex ... – Many file formats and conventions– Many numerical grids (right)
• ... and distributed– Too much data to hold in one place
8Interactive visualization of 4D environmental data
Summary so far
• Predictions need models that are validated by data
• Numerical model data pose several practical challenges
• Visualization of env. sci. data is v. important but complex
• Need to visualize data from lots of different sources
9Interactive visualization of 4D environmental data
Open Geospatial Web Services
(plus many more!)
Web Coverag
e Service
Gridded data(rasters)
Web Map
Service
Map imagery(PNG, JPG, GIF)
Web Feature Service
Simple features
Complex features
10Interactive visualization of 4D environmental data
Web Map Service: a closer look
• GetCapabilities -> metadata
• GetMap -> map image, based on client-selected parameters, inc:– Image width/height– Image coordinate reference system– Style
• GetFeatureInfo -> information about a particular map pixel– Format not standardized
• Supports multidimensional data
• Mandated by EC INSPIRE directive as means for visualizing geospatial data
11Interactive visualization of 4D environmental data
Lightweight visualization methods
• Most heavyweight logic is transferred to server– Pros and cons!
• Imagery transmitted over Web in standard formats
• WMS interfaces (often)• Simple data formats,
Javascript APIs
• Simpler approach, easier to use
• But functionality often limited
NASA World Wind
Google Earth
Microsoft Virtual Earth
OpenLayers
12Interactive visualization of 4D environmental data
Limitations of WMS for science
• Map-oriented– Scientists want to slice data in lots of ways
• Need extra metadata for scientific data– Format not standardized
• Clients and servers often don’t support z and t– (but it’s in the specification)
• Server implementations often slow for high-res raster data– Can’t use interactively
13Interactive visualization of 4D environmental data
A new system: Godiva2• Interactively explore
4D geospatial raster datasets on the web
• ~40 datasets– Research data,
operational forecasts, satellite products
• Images generated dynamically for maximum flexibility
• OGC Website of the Month, January 2008
http://www.reading.ac.uk/godiva2
14Interactive visualization of 4D environmental data
Selection of depth
Select from all the depth levels of the model
15Interactive visualization of 4D environmental data
Selection of time (range)Select from all the timesteps in the model
Selection of a time range leads to an animation
16Interactive visualization of 4D environmental data
Finding the data value at a point
Click on the data layer, data value and precise position is shown
Lon: -64.08 Lat: 36.21 Value: 19.27
17Interactive visualization of 4D environmental data
Timeseries plots
If a time range is selected, can create a timeseries plot at a point
18Interactive visualization of 4D environmental data
Vector plots
19Interactive visualization of 4D environmental data
Selection of colour palette
20Interactive visualization of 4D environmental data
Contrast-stretching
• Manual or automatic
21Interactive visualization of 4D environmental data
Polar projections
22Interactive visualization of 4D environmental data
Choice of background images
23Interactive visualization of 4D environmental data
Export to Google Earth• Allows visualization of multiple
data sources
• Hurricane Katrina, August 2005
• Storm track positions (analysed from ECMWF vorticity data) by Lizzie Froude, ESSC
• Sea surface temperature data from UK Met Office FOAM model
• Combination shows cooling of surface waters on right-hand side of cyclonic storm track
• High winds cause upwelling of cool, deep water
24Interactive visualization of 4D environmental data
Architecture of Godiva2 system
Java Web Application
(Spring, JSP)
Data abstraction layer
NetCDF files Other files
GetCapabilities GetMap GetFeatureInfo Custom metadata
Godiva2website
JSON
PNG, GIF
Generic WMS client
XML
Remote data
OPeNDAP
PNG, GIF
25Interactive visualization of 4D environmental data
Visualizing distributed data:the MERSEA project
OPeNDAP
DATANorth
Atlantic data centre
OPeNDAP
DATA
OPeNDAP
DATA
WMS @ Reading
Dynamic Quick Viewwebsite(= rebranded Godiva2)
Uses existing OPeNDAP-based architecture
Single point of failure
http://www.resc.rdg.ac.uk/mersea
Background imagery(from NASA etc)
Baltic data centre
Arctic data centre
26Interactive visualization of 4D environmental data
Removing the bottleneck:Federated visualization
OPeNDAP
DATA
WMS OPeNDAP
DATA
WMS OPeNDAP
DATA
WMS
Third-party WMS
Background imagery(from NASA etc)
Each data centre must install the WMS
Less network traffic
More robust
27Interactive visualization of 4D environmental data
What is the best use for this?
Have an idea
Discuss/exploreDo the work
Formally publish
Godiva2
Matlab, IDL etc
Disseminate
Godiva2
28Interactive visualization of 4D environmental data
Who’s using Godiva2?• 100,000 GetMap requests served in 3 months
– From 5 continents
• Customized versions of Godiva2 site set up for MERSEA and ECOOP projects– Major EU framework projects – INSPIRE compliance important!– Will be used in MyOcean
• UK National Centre for Ocean Forecasting
• Server software installed by:– Plymouth Marine Labs– AIMS, Australia– NOAA, US
• Code contributions from:– MeteoGalicia, Spain– TPAC, Tasmania– AIMS, Australia
29Interactive visualization of 4D environmental data
Enhancements to WMS• Piecemeal metadata-serving
– avoids large Capabilities document
• Extra metadata for science data– e.g. units of measurement
• New parameters in GetMap for styling:– Choose colour palette– Set contrast range– Linear or logarithmic scaling– Far simpler than Styled Layer Descriptor
• Generation of timeseries plots via GetFeatureInfo
• … but fully backward-compatible with WMS1.1.1 and 1.3.0
30Interactive visualization of 4D environmental data
Interoperability
NASA World Wind
Cadcorp SIS
Google Earth
3rd-party clients can’t use the custom WMS extensions
31Interactive visualization of 4D environmental data
Godiva2 summary
• Godiva2 site is useful for exploring and previewing data– Users need to download data for more sophisticated
analysis– Available as open-source software (http://ncwms.sf.net)
• Have focussed on marine data but applicability is much wider
• Use of WMS standard enables wide adoption and helps to build a community
• Successful example of delivering an application via the web
32Interactive visualization of 4D environmental data
Elephants I have ignored:The three “S”s
• Security
• Semantics
• Scalability
GWS Workshop, Nottingham, June 16 2008 © University of Reading 2008www.reading.ac.uk
Conclusions…
34Interactive visualization of 4D environmental data
Why is it hard to reconcilescientific data and open GIS standards?
GIS ScienceEverything is an attribute of a geographic location
Geographic location is an attribute of data
Map-oriented, i.e. 2.5D (although things are changing, slowly)
Fully four-dimensional data
Well-known, stable coordinate systems
Weird and wonderful coordinate systems (spatial and temporal)
XML is primary exchange mechanism
Data volumes often too large for XML
35Interactive visualization of 4D environmental data
Future work
• Support non-raster data– E.g. In-situ observations
• Support non-map slices– x-t (Hovmuller)– x-z, y-z (depth sections)
• Visualize multiple datasets at once
• Add capability for simple data processing
• Integrate with existing community software– THREDDS, GeoServer, ERDDAP
36Interactive visualization of 4D environmental data
More research needed…• Scalability of servers
– Key disadvantage of service-oriented software!
• “Science profile” for Web Map Service?– Earth Observation profile already exists
• How best to link with Processing Services?– E.g. for data intercomparisons– Service chaining
• Appropriate security methods?• Redesign of OGC services?
– Reveal information (esp. metadata) piecemeal
• Implementation of standards!
37Interactive visualization of 4D environmental data
Some final thoughts
• Geospatial Web Services are all about interoperability
• Interoperability is almost always lossy
• Law of diminishing returns applies
• In science we usually can’t lose any information
• Hence what is the practical limit for application of GWS technology in science?