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Consistent Visualization and
Querying of GIS Databases by
a Location-Aware Mobile Client
A Look at the 2003 Paper by Lodha, Faaland, Wong,
Charaniya, Ramalingan and Keller
Luke Benedict
SE521
March 4, 2009
Agenda
• What are location-aware services?
• What is consistent visualization and what
good is it?
• What are geospatial databases and how
are they used?
• An example of consistent visualization
Location-Aware Services
• Information provided to mobile clients
• Context-sensitive (GPS)
• Can be peer-to-peer and/or from central
location
• Graphical and/or textual
Consistent Visualization
• All nodes on the network see the same
thing
• Comprised of geospatial data, aerial
imagery, CAD drawings, schematics
• Why? Because additional, dynamic, time
critical information may not be available to
the mobile user
Geospatial Databases
• Like a typical database, but has a spatial
element
• Latitude, longitude, elevation, etc.
• Challenge: Different coordinate systems
– State Plane Coordinate System (SPCS)
– Universal Transverse Mercator (UTM)
– Army GRID
Querying Geospatially
• Spatial elements can be stored in
primitives such as:
– Lines
– Polygons
• Can be queried in ways such as:
– Give me all lines, polygons in a bounding box
– Tell me the distance between polygon 1 and 2
Consistent Visualzation
• Differences in coordinate systems must be
resolved
• Clients query based on:
– Location (easiest)
– Coordinates (usually after-the-fact)
– Query (raw, give-me all…)
Example
• Power outage!!!
• Electric company gets a call that a
neighborhood has a power outage.
The First Query
• The power company’s power grid is
described in a geospatial database.
• Based on the neighborhood that is out, an
analysis is done of the network using an
algorithm.
• It is determined that the outage is on a 50
mile transmission line.
Clients Attack!
The Search Begins
• ATVs with GPS-enabled tablet PCs begin to
drive the roads beneath the power line.
• A helicopter overhead flys the line.
• A dispatcher at company HQ guides the
team.
Found It!
• An ATV rider finds the broken line.
Begin Consistent Visualization
• The rider’s coordinates are sent back to
company HQ.
• The dispatcher sends the coordinates to
the geospatial application which uses
various data sources to derive a view of
the situation
• Images, company drawings, voltage info
Example
250 feet high
G4566
Scranton
Substation
#2132
3000
volts
1000
volts
Source
Lodha, Faaland, Wong, Charaniya, Ramalingam and Keller
(2003).Consistent Visualization and Querying of GIS
Databases by a Location- Aware Mobile Agent.
Proceedings of the Computer Graphics International
(CGI’03), 248-253. Retrieved February 13, 2009 from
IEEE Xplore.