Network Based Kernel Density Estimation on Volunteered Geographic Information Applied to Baghdad, Iraq

1. Urban Monitoring Using NetKDE and VGI
Network Based Kernel Density Estimation on
Volunteered Geographic Information Applied to Baghdad, Iraq
Nicolas Lachance-Bernard, Timothée Produit and Loïc Gasser
Geographic Information Systems Laboratory
Ecole polytechnique fédérale de Lausanne, Switzerland
7th VCT Virtual Cities and Territories Conference
October 11th – 13th 2011, Lisbon, Portugal
NLB-TP-LG / p.1 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

2. Content
• Context
• (Network based) Kernel Density Estimation
• Background Case Studies
Barcelona, Ljubljana, Geneva, Baghdad
• Baghdad
Spatio-temporal multi-dimension analysis
• Conclusion and Further research
NLB-TP-LG / p.2 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

3. Context
• Problematic
– Fact
Spatial events location influenced by urban forms
– Principal need
Adapting density estimation for graph constrained space
– Goal
Spatio-temporal monitoring of urban dynamics
• Challenges
1. To use very large datasets
2. To decrease processing times compared to out-of-the-box GIS
3. To develop multi-scale approaches
4. To develop visualization methods
NLB-TP-LG / p.3 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

4. Network based Kernel Density Estimator
KDE NetKDE
Source: Produit et Lachance-Bernard 2009, 2010
NLB-TP-LG / p.4 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

5. KDE vs. NetKDE
KDE NetKDE
Source: Produit and Lachance-Bernard, 2009/2010
NLB-TP-LG / p.5 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

6. Case Studies 2009-2011
Barcelona Ljubljana Geneva Baghdad
(2009/2010) (May 2011) (June 2011) (June 2011)
Network (Agency) 20 km2 (OSM) (Agency) (OSM)
Segments 11,200 8,100 10,800 66,600
Events Eco. Activities Cyclist GPS Eco. Activities War records
Locations 166,300 314,200 15,000 93,100
Class 1 1 12 16 + Weights
Grid 200m 100m 100m 20m 200m 50m
50m 20m 10m -
Gridpoints 160,000 310,000 22,600 - 360,000
Buildings - - 70,000 -
Bandwidths [20m,6000m] [40m,1000m] [200m, 3000m]
-
KDE (Steps) (20m) (20m) (100m)
Bandwidths [100m,1000m] 60m 100m 500m [200m, 3000m]
NetKDE (Steps) (100m) 200m 400m (100m)
Processing 9 computers 1 computer 1 computer 1 computer
times 500h 18h + 77h 15h & 20h &
KDE + NetKDE 5min/class 5min/class
NLB-TP-LG / p.6 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

7. Barcelona Eco. Activities: Grid resolution variations (band. 500m)
H
KDE grid 200m NetKDE grid: 200m
L
KDE grid 50m NetKDE grid: 50m
NLB-TP-LG / p.7 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

8. Barcelona Eco. Activities: KDE vs. NetKDE (10m grid, 500m band.)
H
KDE (ZOOM) NetKDE (ZOOM)
L
KDE NetKDE
NLB-TP-LG / p.8 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

9. Ljubljana
GPS Bike:
NetKDE
20m grid
Bandwidths
A)60m
B)100m
C)200m
D)400m
*Deciles distribution
NLB-TP-LG / p.9 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

10. Baghdad
Case Study
Data
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11. Baghdad Case Study Data: Guardian database
Report ID Report
Information
Date (dd.mm.yyyy) Description
NLB-TP-LG / p.11 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

12. Baghdad: Spatio-temporal multi-dimension analysis
• Events – Wikileaks-Guardian death casualties Baghdad 2004-2009
Coalition Iraqi
Civilians Insurgents
Forces Forces
Attack 86 1,167 1,627 3,775
Direct Fire 482 4,270 4,766 6,807
Indirect Fire 192 284 2,087 1,040
IED Explosion 2,107 5,990 20,228 3,455
Murder 9 2,169 32,563 73
Total 93,157 events 2,876 13,880 61,251 15,150
• Network
OpenStreetMap (66,648 segments)
• Grid
200m resolution 22,644 gridpoints / 50m resolution 362,304 gridpoints
NLB-TP-LG / p.12 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

13. Baghdad IED: NetKDE
NetKDE 800m bandwidth NetKDE 1400m bandwidth
NLB-TP-LG / p.13 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

14. 3D Spatio-temporal KDE*
• Proposed by Demsar and Virrantaus (2010)
based on space-time cube by Hägerstrand
• 3D KDE function
3D Epanechnikov kernel
function
* Implemented by Loic Gasser, Timothée Produit and Nicolas Lachance-Bernard
NLB-TP-LG / p.14 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

15. Baghdad IED explosions KDE
January 2004 - December 2009
• 2,652 events - 1,030 km2 - 76 steps, 1500m KDE
• 1 day equivalent to 10 meters
Source: Loic Gasser, 2011
NLB-TP-LG / p.15 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq

16. Conclusion
• NetKDE for spatio-temporal trends, hotspots, …
– Barcelona: playing with scale and model
How does scale change vision?
– Ljubljana: biking around the city
Where are people most active?
– Baghdad: learn/show using time, classification, weights
When and how are event density patterns change?
• Further work
– Implementation of spatio-temporal NetKDE
– Fixed time comparison (looking for concordances, differences)
Fuzzy-set map comparison
– Automated multi-scale multi-temporal geovizualisation
“Connected-windows” views and annimated-maps
NLB-TP-LG / p.16 Urban monitoring using NetKDE and VGI: NetKDE, VGI applied to Baghdad, Iraq