Transcript Dynamic Map Service Integration

Dynamic Map Service
Integration Tool
Mashing with Google Maps
Craig Wolff, M.S. Eng
CA Environmental Health Tracking Program
Environmental Health Investigations Branch
CA Department of Health Services
Impact Assessment, Inc.
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Map Visualization Principles
• CEHTP and/or system owners provide easy,
systematic, and standards-based access to
GIS data for dynamic interactive
mapping… at any portal
• CEHTP and/or system owners maintain
maximum control over layer rendering
• CEHTP and/or system owners focus
resources on data within their jurisdiction
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Historical Internet Mapping
Paradigm
• Procure hardware, software, staff resources,
• Acquire (often buying) all GIS data to be
used in map service, import into platform,
configure rendering specifications for every
GIS dataset/layer
• Develop a customized browser-based client
to consume map service
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Evolving Map Service Paradigm
• Provide Uniform Resource Locator (URL)
access to commonly used GIS layers
• Give limited choices for visual rendering
• Interface specifications (URL parameters)
for requesting map image follows a
standard (technological or consensus)
– OpenGIS Web Map Service (WMS),
TerraServer, USGS
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Google/NASA Tip the Scale
• Google Earth and NASA Worldwind display
map image tiles of basemap and
satelite/aerial imagery of the whole earth
• Physical air travel by humans decreases
• Google Maps provides easy to use browserbased clients that incorporate AJAX and
fluid rendering of database-cached map
image tiles
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Mashups & Interactive Mapping
• Google Maps API allows interactive maps
with basemap and high-res satelite imagery
on any website … no plug-ins
– See http://www.google.com/apis/maps/
• Hackers figure out how to integrate WMS
content in Google Maps API
– See http://blog.kylemulka.com/?p=287
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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CEHTP Trials/Tribulations
• Two partners to visualize CEHTP pilot project
data through custom interactive map server/client
implementations
• Stumbled through GIS data exchange, metadata,
and appropriate layer rendering
• Loss of control, miscommunication, map
server/client platforms too “closed”
• Need enterprise solution that makes
interoperability, portability, and standards a top
priority
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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DyMSIT Requirements
• Develop server-side utility that overlays multiple map
server image tiles according to [big] client request
• Support for consuming most popular map server
output (ie. ArcIMS, WMS, UMN MapServer, ArcWeb
services)
• Support for individual layer transparency and opacity
• Support for server-side caching (~Google speed)
• Invocation interface is WMS (ie. standard URL access)
• Support for GetFeatureInfo and GetLegendGraphic
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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Recursion on LAYERS parameter
• Recursion: programming technique in
which a function calls itself.
• WMS LAYERS parameter is another WMS
request (or an ArcIMS request or a
MapServer request or a AWS request)
• HTTP encode each LAYERS parameter
• Opacity specified through STYLES
parameter
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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DyMSIT Components
• Servlet container
• DyMSIT Servlet and supporting classes (~1500
lines)
• 3rd party Java libraries: JAI, ArcIMS Java
Connector, GIF encoder/decoder, JDBC driver
• RDBMS to hold cached image tiles (3-field table)
• Javascript library (~100 lines)
cwolff@dhs.ca.gov http://ehib.org http://catracking.com
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