Just a quick note about our progress: we've recently made some significant advances to the data analysis software and have been able to calculate street integration (which is correlated to pedestrian/vehicle traffic) for London and other GB regions using Open Street Map. In the image below the red roads are supposedly the busiest.Even though the algorithm is still being improved we can already start to pick out the main arterial routes which is encouraging (the algorithm doesn't know about the size of roads, just which ones are connected to each other). It is also promising that we can process such as large data set.
Looks good .. but can you leave a clearer definition of what you mean by integration? And accessibility?
ReplyDeleteAlastair,
ReplyDeleteWe'll produce a proper report with definitions and clear descriptions of these measures, but in the meantime here's a short description.
Integration is a measure that can be used as a proxy for vehicle or pedestrian traffic volume. It is commonly used in the field of Space Syntax and is calculated seeing how well connected a road is to all other roads. For example, roads that are connected to many others are usually 'main roads' with lots of traffic, but those that are less connected are often cul-de-sacs or minor roads that have much lower traffic volumes. You can calculate integration just by looking at the structure of the road network, you don't need any other information.
I shouldn't really have confused this formally defined mathematical term with the word 'accessibility' which, as far as I know, doesn't have such a clearly defined meaning. But I take them to mean similar things.
It looks like you've got all the footpaths (highway=footway, highway=cycleway etc) from OSM and some very private roads (e.g. Buckingham Place).
ReplyDeleteThe OpenStreetMap tagging gets quite complicated/bloated/extensive with the highway tag, values you probably want to look at are motorway, trunk, primary, secondary, tertiary, residential, unclassified, service, track, living_street. (selected from http://wiki.openstreetmap.org/wiki/Map_features#Highway) Unless you have decided it is helpful to include footpaths.
Gregory, thanks for your advice. You're right that we need to differentiate between some of the types of roads. Footpaths could be useful though, you've made me realise that it might be worth developing separate estimates for pedestrian or vehicle accessibility. This might be particularly interesting if we want to analyse different types of crime.
ReplyDeleteI have just read "Mapping the East End Labrynth" and I would like some suggestions on how to step into further detail as it regards flow of pedestrians and historical evidence. Thank You
ReplyDeleteDave, could you be a bit more specific? I'm not entirely sure what you would like to achieve. Presumably you are aware of the Space Syntax work at UCL?
ReplyDelete