Tuesday, 6 December 2016

Can't see the wood for the trees

The Mayor of London's office recently published the London Tree Map. Like other similar maps of major cities (e.g. New York, Melbourne) it 'suggests' by its very existence that it's a map of every tree on the streets of the city.

https://maps.london.gov.uk/trees/
(Click to open the actual map in a new window)

The map looks decent enough and I was compelled to head to the London Datastore to take a look at the data myself to see if there was value in playing with it.

The main map page is clear to say the map is 'an initial attempt' to present the tree data but when you dig into the small print, in fact there exists a number of issues including:

  • incomplete coverage from different Boroughs
  • surveyed dates are unknown and likely prior to the date specified
  • no agreed or consistent framework for the data collected
  • lack of naming conventions for recording species

The data represents an uncoordinated set of efforts to collect information. I'm fine with that; and also that they are highlighting these drawbacks. But, how many people are going to go beyond the map and dig into the veracity of the data? As with most (all?) maps, this one lies but this one tells huge porkies! With an estimated 8 million trees in London, this is likely only 10% and the data is so fraught with possible error it makes even this 10% questionable.

Publicising such a map leads to misinformation. It's duplicitous by the very act of it being published though I am in no way suggesting those behind it did so intentionally.

A couple of the geo-twitterati thought I was being overly harsh, suggesting "it's a good start", "it's better than no map at all", "it's just an attempt", and "I've seen worse", I don't disagree with these sentiments (and yes, there are way worse maps on the interwebs) but these sort of comments gloss over my general point. Whatever you put on the internet becomes THE view of reality regardless of the quality of the data. In this sense, this map becomes THE view of the pattern of trees in London. There's no getting away from that reality and it does the subject matter a disservice in my opinion.

My suggestion is simple. If you have access to data like this, be careful and seriously consider not mapping it until you've dealt with the errors and inconsistencies. I appreciate that one of the first acts when you have data is to stick it on a map but sometimes restraint is the better path.

All of the same points about raising awareness and issuing a call to action for a framework for consistent and thorough data collection can be made without making a map that lies so badly. At least the unsuspecting public won't get fooled quite so much,




1 comment:

  1. This is as old as the hills. 1986 Edmonton, Canada were not allowed to publish maps, which among other things correlated pit bull terrier ownership w break&entry perps. In 1996 Halliburton pulled a webmap showing Saharan oilfields in their glorious polluting detail, giving black&tan a whole new meaning. And in 2006 an Esri book was pulled on biz demographics coz it lent itself to exactly what u said #welcome2mynightmare (apologies 2 Alice Cooper)

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