With the availability of Open Data from the Ordnance Survey and some of the really interesting publicly avialable data from web sites such as the London Data Store and data.gov.uk some intriguing maps and analysis can be performed. Here is an example I recently created in ArcGIS Desktop 10. It shows the commuter movements of Londoners by borough. You can clearly see that central London tends to have a net migration inwards (red dots) and the boroughs outside central London tend to have a net flux outwards (blue dots). The bigger the dots, the greater the movement. I guess that’s not surprising really!
The base data is made up of a couple of OS OpenData layers, specifically the boundaries are Boundary-Line and the rest of the detail is Strategi. I took the CSV of the Commuter movements from the London Data Store and joined this to OS Boundary-Line.
To symbolise the commuter movements of each borough polygon I used a combination of graduated symbols to create the desired affect. I created three separate layers of the same information but being symbolised in slightly different ways.
The image above explains how I did this.
I then created a definition query on each layer as follows:
Top symbol: ”CODE” LIKE ’00%’ AND “OutOfAreaB” > “IntoAreaA”
Middle symbol: ”CODE” LIKE ’00%’
Bottom symbol: ”CODE” LIKE ’00%’