3D Visibility with Vector GIS Data

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1 3D Urban Visibility Analysis with Vector GIS Data SULEIMAN Wassim 1 , JOLIVEAU Thierry 1 , FAVIER Eric 2 1 ISTHME-ISIG CNRS/UMR EVS, Université Jean Monnet - Saint-Etienne. 2 DIPI EA 3719 École Nationale d'Ingénieurs de Saint- Etienne [email protected] [email protected] [email protected] 19th annual GIS Research UK (GISRUK) - University of Portsmouth - 27 th -29 th April 2011

description

The visibility estimation has an important impact in many economical and aesthetic fields, a mixed environment which contains madman objects like buildings with relief sol make a challenge for the visibility calculation. This paper presents a new method to solve this problem based on vector GIS data. The use of vector data gives the possibility to calculate the intervisibility, viewshed for mixed environment. The new method could identify the obstacles (relief, buildings identification) which block the visibility for a 3D environment points from observator, the intervisibility impact of a specific building could be calculated

Transcript of 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]

[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)

wassim
and voxel numbers
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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

wassim
nombre de bâtiments ? C’est difficile de définir il y a 233 polygones mais en vrais bâtiments (connecte complexe) il y a environ 40
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A regular grid of viewpoints

wassim
in this slide point every 10 m
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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

wassim
I try to explained with some drawing the docx file
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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

wassim
in this slide point every 10 m
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Global 3D intervisibility interpolated map

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Result : 3D Isovist calculation

wassim
(Yes it is true Isovist but I use viewshed because it is used in the literature with raster)
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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

wassim
this depend of the level change if the change is not high (the ground is flat) we can reduce the points number up to 80% if there is a lot of change in level the reduce in points number is about 40%
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Simplifying the buildings polygon

The extra collinear points were eliminated

Original building polygon Simplified building polygon

wassim
We reduce the points number for the polygon representation (30% - 60%)
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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