3D Visibility with Vector GIS Data
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3D Urban Visibility Analysis with Vector GIS Data
SULEIMAN Wassim1, JOLIVEAU Thierry1,
FAVIER Eric2
1ISTHME-ISIG CNRS/UMR EVS, Université Jean Monnet - Saint-Etienne.
2DIPI EA 3719 École Nationale d'Ingénieurs de Saint-Etienne
[email protected] [email protected]
19th annual GIS Research UK (GISRUK) - University of Portsmouth - 27th-29th April 2011
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Visibility analysis Fields of use :
■ Urban and landscape planning■ Navigation systems■ Visual surveillance
Measures in view assessment ■ Inter-visibility ■ Isovist and viewshed■ Global visibility
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Main technique : ray tracing
2D Vector data
2.5D Raster data
Brossard & Wieber
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3D ?
Wii home
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Entities ?
Source : DSS for Coastal Protection Design by Cdr.Phinai Jinchai
Public Eye
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One idea : 3D Voxel model
Ray tracing
(Pyysalo et al. 2009), (Morello & Ratti 2009)
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Another idea in vector mode
3D polygon plane facets (terrain, building)
3D environment considered as a constellation of polygons■ TIN terrain model + ■ 2D footprints with height extrusion
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A regular grid of viewpoints
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3D Data Model
building
wall
roof
terrain facet
view point
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Data and Tools
Data■ Totopographic Database of IGN
Tool■ Matlab
Easy of use Rapid prototyping/debugging of sophisticated code Tools for GIS data import and export from ArcGIS (Mapping
Toolbox) Tools for simulation and data analysis (Symbolic Math
Toolbox, Parallel Computing Toolbox, Statistics Toolbox, Optimization Toolbox)
Easy rapid visualisation ■ ArcGIS
Interpolation, visualisation
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Principle of the computation
If Test1 and Test2 is verified then there is no intervisibility between the two points
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Principle : intervisibility between two points connected by a segment ?
Polygon / Segment intersection in the 3D environment ?
Polygone
Segment
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Step 1: Find the plan of the polygon and the line of the segment (3D)
Plan
Line
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Step 2: Find the Intersection point between the plan and line (3D)
Plan
Line
Intersection point
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Step 3: Check if the Intersection point belongs to the polygon (2D) (Test1)
Plan
Intersection point
Polygone
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Step 4: Check if the Intersection point belongs to the segment (Test 2)
Line
Intersection point
If the results of tests 1 and 2 are true, the segment and the polygon intersect.=> the polygon blocks the visibility between the extremities of the segment
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Global intervisibility results
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Global 3D intervisibility interpolated map
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Result : 3D Isovist calculation
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Building 3D intervisibility effect
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Order of complexity of the algorithm Function of :
■ the number of the grid points■ the number of the polygons in the 3D
environment
Necessity to reduce the number of the 3D polygon by simplifying the TIN model
and Building
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Simplifying the DEM
Eliminating extra points in the same level (IsoLevel) within 1 m height interval parameter
DEM DEM with IsoLevel simplification
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Simplifying the buildings polygon
The extra collinear points were eliminated
Original building polygon Simplified building polygon
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Results of 3D simplification
The execution time is 2 times faster Negligible change in the intervisibilty map
and viewshed map (less than 5%)
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Future work
Vegetation layer “Real” 3D Isovist Points on the building facades More complex buildings
models Implementation in GIS
software
Decouvrir Arc de triomphe
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Thank You
Images sources : Woo home : http://www.woohome.com/photograph/steep-hills-of-san-francisco DSS for Coastal Protection Design by Cdr.Phinai Jinchai http://www.dss4cpd.com/dmain/index.php?q=node/26Public Eye : http://www.globalsecurity.org/eye/html/wtc_noaa_wtc3.htm Decouvrir Arc de triomphe : http://decouvrir-arcdetriomphe.blogspot.com/2011/04/quizz-anecdotes.html