Crow flies, why do people still use the circle based approach?

Crow flies, why do people still use the circle based approach?

For many years, I have dreamed of being able to fly, fly over buildings, over water and have no issues with congestion.  It would be brilliant, I’d be able to get everywhere quicker, leave later and have more time for myself.  Unfortunately, I’m not blessed with wings and don’t quite trust jetpacks.  I have pretty much come to terms with this, but every time I look at one of the maps generally scattered around London and other towns and cities telling me I can walk this far in 5 minutes, it always shows this as a crow flies approach, not considering all these pesky things such as water and buildings that I can’t “fly” over.

With my background in mapping and close links to both Local Authorities and Ordnance Survey, I know that they have access to much more detailed data that can give them more accurate maps, for not much more effort.  Why give bad information when this can easily be reciftied? Many large cities and towns are built on our historic waterways, splitting them in two and crossing points are essential to keep people connected.  I therefore decided to test some of the crow fly maps in our market leading TRACC software, utilising detailed Ordnance Survey Highways data. This dataset includes millions of links showing footpaths and walking routes for all Great Britain and is available for free as part of the PSMA for Local Authorities.  I took photos of various signs I have seen in London, represented these circles in TRACC and then compared the actual walk times to see how they compare: –

Oxford Street

The first map shows the circle of Oxford Street, interestingly the 15-minute walk to the East and West are pretty much spot on. However, when you take into account access points for Hyde park and the street design, the other areas around the map come up short, although are not too bad with the outskirts only being a couple of minutes out.

Hammersmith

I took this original photo on the way to doing a demo for the Borough a few years ago and it was one of the photos that I first saw that made me think about the issue.  The sign in question was located next to the Thames showing a 15-minute walk zone going straight over the Thames.

When you look at the actual walk time in TRACC you can see that many areas on the other side of the Thames are outside this walk zone and when you investigate further some of the furthermost areas would in fact take half an hour to walk to!

Vauxhall

Like the Hammersmith map, the water is creating a natural barrier. However as the location is right on Vauxhall bridge, the effects are not as extreme, though again both bands are overestimated as they don’t consider the streets and houses creating natural barriers.

These maps offer far more accurate outputs for little additional effort.  Clients and customers are impressed at the ease in which these walk zone maps can be produced and the positive impact they can have.  An example of this is where a local authority saved thousands of pounds and resulted in a 27% increase in active travel by producing accurate and easy to understand walk zone maps.

So with all this great data available for use, why would you choose a crow flies map?

Dan has over 10 years experience as a Product Manager at Basemap looking at the full product life cycle using AGILE/SCRUM and liaises between key stakeholders and developers to ensure first class applications are built. He is the resident expert on data and software solutions that Basemap offer its clients.