New MapRoulette Challenge: Ways Needing Smoothing

Posted by mvexel on 18 March 2014 in English (English).

Those first few MapRoulette challenges did not keep you busy very long: most tasks in the Zorro / Tangled / Wrong One Ways challenges were fixed within the first few days. Dang! We were not prepared for that and had to take MapRoulette down for a little while because there was nothing to do…

But now we’re back! This time with Ways Needing Smoothing. We detect ways that have suspiciously sharp angles and ask you to smoothen them out. Here’s a great example:


Opening this task up in JOSM reveals that there’s more to fix than just the one sharp angle that was detected:


This is typical for the US TIGER data - poorly aligned ways that are either under- or overnoded. And there’s still a lot of them! We detected over 100,000 cases, not all of which are loaded for this challenge yet.

This challenge is bound to have some more tasks than usual that are not ‘real’ errors - that is the nature of challenges of this type. Just skip over them and mark them as ‘not an error’. They will not show up again.

Oh and finally - a cool new little feature is the permalink: you can now link to any task you encounter and want to discuss or share. The link for this one is

Happy mapping :)

Comment from RoadLessTraveled on 19 March 2014 at 00:22

Ay ay ay… I just spent some time going through some of these smoothing challenges… some of them are really bad! And they just seem never ending. What’s really interesting is that most of them seem to be pretty much the same errors again and again: a small road curving between two larger roads at a sharp angle… three nodes on a larger node bumping outwards where a smaller road meets etc.

Comment from mvexel on 19 March 2014 at 23:43

They are almost never ending….I only loaded the first ~6000 of them, around 90000 more to go after that…

Comment from Rps333 on 21 March 2014 at 22:36

Great way to kill time. Spent a few hour on it, while I waited for my plane.


Comment from hobbesvsboyle on 24 March 2014 at 13:55

Nice challenge. I noticed that there are a lot of false-positives with highway off- and on-ramps. Maybe it would make sense to filter those out for the remaining 90000?

Comment from hobbesvsboyle on 24 March 2014 at 15:30

Another observation: Some of the ways I came across had 5 or more changes in the last few days, presumably all related to the roulette. How many times does a task get assigned before it is marked as fixed?

Comment from Stalfur on 31 March 2014 at 13:26

Very interesting. How would I go about in creating MapRoulette challenges for a totally different area? Specifically thinking of my Mapping Botswana project here…

Comment from mvexel on 31 March 2014 at 18:05

hobbesvboyle: The tasks need only one person to say it’s fixed (or not an error) for them not to appear again. The reason you are seeing what seems to be the same task twice is that the logic that detects these sharp angles sometimes operates on parts of ways, so one way that has multiple sharp angles may appear twice. Also, folks often choose to load a bigger area once they fixed the error, as it’s often obvious that there’s more things to be fixed. In the process, they may be fixing what are separate tasks in MapRoulette :)

Stalfur: I am writing up a challenge creation guide. I will post a diary entry when that is done.

Comment from Katie U on 18 April 2014 at 14:40

Is there a recommended frequency of nodes on ways? I just marked as not an error a way that seemed to have nodes every 5 feet. The effect was a very smooth sinuous mountain road.

Comment from hobbesvsboyle on 18 April 2014 at 19:36

@Katie U: I’ve encountered lots of those in MA where they seem to come from an import. I usually simplify those ways (NOT using JOSM’s default setting, as its way too coarse) and then manually confirm that things look good. Usually I have to add in a few nodes again.

Comment from mvexel on 18 April 2014 at 19:49

Katie: there’s no strict rules! As many as you think makes it look decent. Be sure however that you are zoomed in far enough to really see the road well on the aerial image. (You should be able to see the markings on the road, and cars, if there are any.) I would also suggest that that it’s not necessary to put any additional nodes on straight parts of the way, as those do not add any useful information.

Comment from hobbesvsboyle on 28 April 2014 at 20:18

Are we all done with the challenges or is maproulette broken at the moment? I can’t get it to load any further tasks.

Comment from rickmastfan67 on 29 April 2014 at 09:41

Yes, I’m having major problems with maproulette right now too. I’ve been lucky to load only a few challenges over the last ~3 days. The initial challenge loads, and then I can’t get the next one to work, even if I fix the one that did load or even mark it as it wasn’t a mistake (if it really was a mistake of course).

Comment from mvexel on 10 May 2014 at 15:36

Sorry for the intermittent problems, folks! I hope everything works well again now.

We actually added a new feature, more about that in a new diary entry soon. It’s already live on - can you find it? :)

Comment from rickmastfan67 on 5 June 2014 at 08:59

I think I know what that feature is Martijn. hehe. I will not post what I think it is here (so not to spoil your future diary post about it if I’m correct), but I did just shoot you a PM with my guess if you want to tell me if I’m right or wrong. ;)

Comment from Harry Wood on 22 July 2014 at 14:35

Clicking through some of these today, it seems the majority of them are already fixed and already re-rendered as better smoother curves. Seems like this maproulette challenge needs a data refresh?

Comment from mvexel on 22 July 2014 at 15:16

It does, Harry, and I apologize! There is something going on either on the challenge provider’s end or on MapRoulette’s end and my mission for today is to figure out what it is!

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