I have been digging through the Lewisham Tree Data in order to try and discover some useful insights.
The data published by the Council contains information on Ward, Geographic Location (Easting / Northing), Age, Condition & Height but unfortunately contains nothing about ‘where’ the tree is located, e.g. whether the tree is in a park or cemetery, on a street or in another Council owned location. As this campaign is concerned primarily with street trees my first step was to enrich the data to include these categories.
To analyse and present the data I am using an excellent tool called CartoDB which allows location data to be imported, queried & mapped. In order to allocate the different categories (Park Trees, Street Trees, Other) I imported the Lewisham Tree Data as well as ‘shapefiles’ containing London’s parks, recreational areas & roads (available via OpenStreetMap).
The exact details are fairly technical (& will be saved for another blog) but the logic I applied is as follows:
- If a tree is within a park, cemetery, recreation ground, pitch or allotment then it is a ‘Park’ tree
- Otherwise, if a tree is within 12 metres (determined by trial & error) of the centre of a road then it is a ‘Street’ tree
- Otherwise it is categorised as ‘Other’
The outcome of this can be seen by applying the new ‘Category’ filter on the map : maps.catfordstreettrees.org.uk
Now that each tree has a category, queries can be run to look at things like:
- % Street Trees vs % Park Trees
- Street Trees per ward
- Street Trees per square kilometre
Street Trees per square kilometre
The first of these that I tackled was looking at the number of street trees per square kilometre for each ward and the results are as follows:
|Trees per km²|
|Ward||Area (km²)||Tree Count||Trees per km²||Park Trees||Street Trees||Other|
(NB. Table sorted from least to most street trees per square kilometre)
As shown, Downham is at the bottom of the list for ‘Tree Count’, ‘Tree Count per km²’ and ‘Street Trees per km²’. Rushey Green and Catford South are doing slightly better but are still in the bottom half of the table, with almost 1/3 and 1/2 as many street trees as the top of the list, Telegraph Hill.
I’m uncertain if ‘Street Trees per area’ gives the best measure to compare the different wards therefore I am going to keep digging into this dataset to see what other insights I can find – more to follow.