When maps are biased

20 Dec

Maps are simplifications of reality and by their very nature introduce bias based on what they include and what they leave out. Unfortunately most current maps have a bias towards the car given that they leave off most of the detail that matter only to pedestrians and to public transport users. This problem is compounded when the maps produced by authorities specifically for these user groups also leave of the relevant details.

This problem was demonstrated very clearly to me today while we were delivering some xmas cards on foot today. We delivered our first card half way down Beech Road and then needed to get to the southern end of Cambridge Road as shown on the following map from Google. This map has an amazing amount wrong and is almost completely useless for walking directions as you will see as the post develops. From this map it would seem sensible to head north then east along the busy Woodbridge Road and then all the way down Cambridge Road.

Google Map

Actually, I knew that there was a convenient set of footpaths missing from this map so we set off south to pick up a footpath that went up through the woods from Mendip Drive and then east along a short path. The paths are shown on this map from OpenStreetMap. The small blue squares are bus stops btw.

openstreetmap take 1

However, we then spotted a footpath I didn’t know about which seemed to be going in the right direction. We asked someone getting snow off their car if it would help, but he told us to go up to the main road as per the Google map. I knew that wasn’t right so we completed the trip as already planned going down to Mendip Drive. The clever bit about OpenStreetMap is the edit feature, so when I got home I pressed edit and added the missing path and the map now looks like this – notice the additional path.

openstreetmap take 2

What is clear to me is that the guy cleaning was using a mental model based on the roads as supported by the Google mapping. It gets worse though.. There is also a mapping website called walkit.com which aims to address this limitation with other mapping and which, as you might have guessed, promotes walking. Unfortunately it doesn’t have these paths on either and recommends the route as Google and the car driver! notice that there are no bus stops marked either.

Walkit.com recommended route

And then there is the local official cycle map published by Suffolk County Council which also misses the paths off!

official cycle map

And now lets look at the local bus map which also misses all the footpaths and curiously doesn’t even show the positions of the bus stops which seem to be kinda important to public transport users.

Bus map

What is going on here? OpenStreetMap which is produced and maintained by volunteers like me is available for free and is very accurate.The official cycle map which is produced at significant expense by Suffolk County Council, the local instance of Walkit.com which was commissioned and paid for by Ipswich Borough Council and the local bus map which is produced by the local bus company all largely reinforce the car drivers view of the world by leaving off this critical detail!

I will again recommend that that stop spending money on these resources and promote OpenStreetMap as Microsoft do with Bing Maps which  can now display OpenStreetMap data. OpenStreetMap data can of course be used as the map base for all of the above specialist local maps if necessary.

Bing maps supports openstreetmap

2 Responses to “When maps are biased”

  1. Kathy December 21, 2010 at 11:26 am #

    Hi Peter

    Apologies that walkit.com did not generate the route you expected. As there are no “off-the-shelf” data-sets with which to build a pedestrian planner, we do the majority of the development work ourselves. Whilst we endeavour to include all public footpaths, cycle-paths and alleyways, unfortunately we do miss the odd shortcut.

    We do rely on local knowledge to ensure our data is as comprehensive as possible, so thank you for bringing the missing paths to our attention. I have now studied the area in detail, and have added a number of missing footpaths to our data. This information will go live on our site in the new year. Please do get in touch if you experience any further problems or missing data on walkit.com.

    Kind Regards,

    walkit.com team

  2. Peter Miller December 21, 2010 at 11:39 am #

    Thanks Kathy. You may be aware that I have previously been in touch with walkit in relation to other issues in the Ipswich area over the past year, however there are still numerous paths missing from the map. Compare the detail in Walkit and OSM for the Chantry area of Ipswich to see one seriously deficient area.

    I have recommended to yourselves and to Ipswich Borough Council that walkit switches to OpenStreetMap as its base mapping in places where good data is available. In that way you gain all the local knowledge that is in OSM, updates are easy and in addition your mapping efforts can be shared with other applications such as cyclestreets who do cycling routing. Currently you are fighting an open data set which is getting better by the day. For the avoidance of doubt OpenStreetMap can not be used as a free source of data to update and improve other closed routing datasets (such as Navtec), it should be used as a complete data set in place of the commercial source.

    A group of us are aiming to complete Suffolk very soon to the road level and to the urban footpath level where there has been a ground survey or where the aerial photography is good enough on its own.


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