History Workshop at SotmBaltics

On the Sunday morning of the State of the Maps Baltics Susanna Ånäs had organised a workshop on mapping historical geographies.

Getting the History mapping workshop underway
Senate Room, University Main Building, Tartu

Persistence in the Urban Environment : 2 Portland Oregon Buildings and experimental clustering

Areas of the Mutlnomah County, Oregon grouped into 5 clusters based on patterns of building age.
Each building is plotted individually using the colour assigned to its own cluster.
(data from City of Portland Open Data Initiative, background OSM)

A few months ago I wrote about how different parts of cities have radically different development patterns. I illustrated this with examples from three cities which I am familiar with, but all my interpretation was subjective. I was therefore very interested in a blog post by MapBox about the Open Data building footprints for the metro area of Portland, Oregon. Apart from the fact that this is a comprehensive data set the most interesting thing is that most (around 87%) of the buildings have a data associated with them. It therefore seemed like a perfect data set to see if one could classify areas of a city in terms of the profile of building activity.

My basic idea was to do something along the following lines:

• Partition the buildings into contiguous equal sized groups
• Create some kind of time-series for each group reflecting building history
• Run a clustering algorithm against the latter data
• See if it produced interesting results

Persistence in the Urban Environment : 1

Anyone reading this blog should have realised that I am interested in using maps to understand how the environment we live in has changed over time. I know I share this interest with many other OSMers. There have been many proposals, and discussions about how we might use some of the principles and technologies of OSM to create maps representing an area at some historical time point. I am greatly heartened that a new mailing list (http://lists.openstreetmap.org/listinfo/historic) has appeared for interested parties to share ideas on this subject:

Wollaton Park Estate from the E, (June 1928)

One problem which has exercised my mind, and particularly from my exercise at looking at the OSM edit history of Berlin, was how adding a history (or time) dimension to geographical data might impact on data volume. In thinking about this I have been struck that a very large proportion of the urban environment of cities in Europe and North America is remarkably static. This was brought home by the recent availability of historical aerial photographs of Great Britain (at the Britain from Above website).

Wollaton Park Estate on OSM