1. 3D Intervisibility: takes the
wonder out of wandering
Dr Neil Stuart, Dr Fraser MacLeod
ns@geo.ed.ac.uk,
fraserm@terravistaltd.com
University of Edinburgh, terraVista ltd

2. ENTER 2004 Research Track Slide Number 2
Naïve Geography

3. Enhancing Naïve Geography
Information Interaction Mobility
ENTER 2004 Research Track Slide Number 3

4. LBS Shortcomings
• ‘Effective’ LBS?
• Limits of LBS with 2D landscape models
– ‘Close’ but NOT ‘visible’ features
– network of paths NOT open country routes
• Design innovation needed
– “a better match with people’s thinking”
– Exploring landscape visualisation
ENTER 2004 Research Track Slide Number 4

5. terraVX Differentiators
• Step into third dimension
• Analytical approach
– intervisibility
– open country navigation
ENTER 2004 Research Track Slide Number 5

6. Factors Affecting Visibility
• Data issues:
– Digital Terrain Model (DTM)
– Resolution of terrain data
– surface features that impair visibility
• Digital Surface Model (DSM)
• Other sources of uncertainty
– How high is the observer’s eye-level?
– How clear is the air (weather conditions?)
ENTER 2004 Research Track Slide Number 6

7. Viewshed Computation
• Viewshed of single point
– the parts of terrain that can be seen from one
point
• Analysis well known
• Considered one of the more processor
intensive GIS tasks
ENTER 2004 Research Track Slide Number 7

8. Sample Viewsheds
ENTER 2004 Research Track Slide Number 8

9. DSM vs DTM
Surface Features
(DSM)
Terrain Only
(DTM)
ENTER 2004 Research Track Slide Number 9

10. terraVX Intervisibility
• Digital Surface Model
• Complete Intervisibility
• Geo-referenced features
• terraVX database
• Prioritisation rules
ENTER 2004 Research Track Slide Number 10

11. terraVX Guidance
• Topology well known, but ...
• Terrain rules
• Topographic map input
• Suggested route
• terraVX database
• Secondary development stage
ENTER 2004 Research Track Slide Number 11

12. terraVX Challenges
• Availability of digital terrain data
• Building pervasive terraVX databases
• Implications for content
• Urban canyons!
• Data volumes, updating, and maintenance
ENTER 2004 Research Track Slide Number 12

13. terraVX Architecture
ENTER 2004 Research Track Slide Number 13

14. terraVX
• Simple interface
• Belies complexity
• Feature list
– Visible
– Not visible BUT close
• Browse information
• Location bookmarks
ENTER 2004 Research Track Slide Number 14

15. Conclusions
• Sight drives perception of our surroundings
• 3D landscape models better match
• Visibility paradigm
• Open country guidance
• Industry standards
• Power of geo-computation
• Inherently scaleable architecture
ENTER 2004 Research Track Slide Number 15

16. ENTER 2004 Research Track Slide Number 16
terraVX: intervisibility to insight