Transaction Management in Database Management System
SSS8 - From the Axial Line to the Walked Line
1.
2. Background:
This study stemmed from the preparatory work for the Bartlett,
UCL research project Adaptable Suburbs
Project Team: Professor Laura Vaughan, Dr Sam Griffiths, Professor
Muki Haklay, Dr Claire Ellul, Dr Victor Buchli, Ashley Dhanani and
David Jeevendrampillai
‘Astudy of the relationship between networks of
human activity and the changing form of urban and
suburban centres through time’
3. Origin of this study:
For the Adaptable Suburbs research project the street network
system of London has to be reconstructed for four historic periods
and analysed.
The question that originated the evaluation of the street network
data was: ‘Which data sets should we use as the basis for the
reconstruction of the historic street network of London?’
Three network datasets were available to us for this study:
1. Commercial: Ordnance Survey Integrated Transport
Network: ITN
2. User Generated: Open Street Map: OSM
3. Reference: Pre-existing Axial Space Syntax Model of
London: Axial
9. Comparison of network length and number of segments
London wide network (2,900km2)
OSM ITN AXIAL
Total Length (km) 29,700 26,027 20,039
Number of Segments 718,118 1,213,646 453,562
Surbiton case study network (110km2)
OSM ITN AXIAL
Total Length (km) 1,456 1,197 1,075
Number of Segments 37,585 58,293 20,637
10. Space syntax analysis of Surbiton case study network models
- Analysed in Depthmap.
- Angular segment analysis of choice and integration.
- Utilised segment length weighted analysis (Turner, 2007) for road
centre line data to compensate for many shorter lines.
- Results compared visually as direct comparisons of values are
very difficult in such dissimilar network models.
11. Axial Model ITN Model OSM Model
Surbiton - Choice Radius n
12. Axial Model ITN Model OSM Model
Surbiton - Choice Radius 2000m
13. Axial Model ITN Model OSM Model
Surbiton - Integration Radius n
14. Axial Model ITN Model OSM Model
Surbiton - Integration Radius 800m
15. Topological step depth analysis
Topological Step OSM ITN AXIAL
Depth
Mean 90 197 49
Median 94 204 50
Maximum 197 422 90
Mode 106 224 44
17. - All models show the same structur
growth in regards to segments over s
-Although with very different number
Segments involved.
-Axial model is a simplification of the
structures and road geometry.
18. Connectivity analysis
-ITN and OSM show the same connectiv
properties.
-Axial model shows very different co
structure.
-Further evaluation required of conn
properties.
19. Summary
ITN – Most reliable and complete data set but it is
too detailed for space syntax analysis and
therefore must be cleaned to remove extraneous
features. Lacks non-road routes through the
urban fabric – represents a model of vehicular-
accessible network.
OSM – Not reliable in its coverage or methods of
data creation but it is a very interesting
representation of the city as seen through the
eyes of those who inhabit the space. Contains
features that commercial data does not. Useful as
supplementary data.
Axial – This is a different entity to the other
models. It represents space in a completely
different way. A powerful model but extremely
time consuming to construct. Questions as to its
representation of complex features – not enough
20. Conclusion
Work has to be done to reconcile the underlying
model of space and its implicit account of what is
meaningful in space with the analytical toolkit of
space syntax analysis.
-Vital in further developing angular
segment analysis.
-Integrating street network and built
form for holistic analysis of urban structure
and function.
Analysis raises important questions as to what
should be represented and how: pedestrian-only
routes, angular changes in street alignment, etc.
The question of how we represent the real-world
through data is one that must be carefully
considered otherwise the analysis that stems
from it can be easily undermined
