Richard has commented on the following diary entries

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It's not because you have accurate data that you have to upload all of them in OSM 6 days ago

Splendid. Ok. Here's your challenge.

Write some polyline simplification code that reduces [1,0],[2,0],[3,0],[4,0],[5,0],[6,0] to [1,0],[6,0], yet is completely lossless.

Any programming language of your choosing. It's very doable.

Second task, since you ask for "challenges" (plural): adapt that simplification algorithm to permit minimal loss of geometry within the bounds of feature width and GPS accuracy. You may choose to implement an adjustable threshold as part of this.

It's not because you have accurate data that you have to upload all of them in OSM 7 days ago

"All simplifying algorithms lose information"


If you have a polyline [1,0],[2,0],[3,0],[4,0],[5,0],[6,0], you can simplify that without any loss of geometry to [1,0],[6,0].

If you have a polyline [1,0],[2,0.0000000001],[3,-0.0000000001],[4,0],[5,0.0000000001],[6,0], you can simplify that (units permitting) with minimal loss of geometry to [1,0],[6,0].

"Minimal" is in the eye of the beholder, but given the width of the features we survey in polyline form in OSM and the positional accuracy of GPS units, it's clearly >0.

Still, as both Vincent and I are only editor coders, what the hell do we know about how these things actually work, eh, Rovastar?

It's not because you have accurate data that you have to upload all of them in OSM 7 days ago

Given JOSM users' proclivity to demand that every single possible error is trapped by iD (cf and P2, I think we should quit ragging on Ragi, and instead JOSM should refuse to upload unnecessarily detailed ways like this. It's the responsible thing to do. ;)

Third Anniversary of Mapping in the Peak District National Park 8 days ago

That's terrific!

Funny highway shortcuts with the new routing feature 9 days ago

[For the avoidance of doubt, my comment was a reply to the original posting, not to Rovastar's comment which was posted at the same time.]

Funny highway shortcuts with the new routing feature 10 days ago exactly why we've added routing to the front page!

Large amounts of OSM data is unsuitable for routing. Putting routing front-and-centre means this will get fixed. Thanks for fixing this one and I hope you find many more such bugs to fix. :)

Fixing the rural US about 1 month ago

@Alex - interesting, and good to see Mapbox tackling this.

Have you thought about running an automated comparison with Arnold (as you blogged at I'd expect that any road showing on Arnold is of reasonable quality; if the corresponding geometry in OSM is tagged with highway=residential, tiger:reviewed=no, that suggests a priority for retagging.

One example I found just by zooming into Eric's Arnold rendering: here in WV there's a highway=residential which has moderate traffic flows and should really be a tertiary.

Fixing the rural US about 1 month ago

@jumbanho: Yes, I can see the logic in that. Essentially, as long as unpaved roads are tagged as such, that's great. (What's a little more worrying, and something I've encountered several times, is when people retag these gravel roads as highway=unclassified without adding a surface tag.)

Learn-a-tag: driving_side=left/right about 1 month ago

I wonder how you'd tag the short section of the River Cam where boats should follow the left bank, as opposed to the right bank (which is standard everywhere else on the UK waterways). 'driving' doesn't seem the correct word for a boat but maybe I should just let that slide...

Fix a Forest - experimental tiles from US Forest Service data about 2 months ago

@mojodna: Just posted it on github - does this help?

Voting is bullshit about 2 months ago

Agreed 99%.

The 1%: I don't think it's data consumers who are responsible for this mess. It's tidy-minded people trying to second-guess data consumers. If these tidy-minded people had actually used OSM data they wouldn't be coming up with batshit insane proposals.

At, I suspect I do more detailed analysis (for both routing and display) of paths than any other data consumer. The two most notorious wiki-inspired tags, highway=path and smoothness=, haven't made life any easier for me; they've made it a whole lot more difficult. When highway=path is used without a vast array of supporting tags, which is the case the majority of the time, it's impossible to guess sensible defaults. smoothness= is just a plain bad tag in ways which are too numerous to recite.

Or in other words:


Rising participation in the discussion of tag definitions 2 months ago

You can read and post to the OSM mailing lists via a forum interface using Nabble or Gmane. Here's the Nabble pages for tagging@:

How to improve OSM: kill the bureaucracy 3 months ago

Please no! Imports really aren't desperately needed in the US. What's desperately needed in the US is for more people to clean up the disaster area that was the first import of all, TIGER, rather than piling more and more unmaintained, out-dated data on top.

How to improve OSM: kill the bureaucracy 3 months ago

Being a newbie 3 months ago

Brilliant post. Spot on.

We probably need to make (future) private messages into public messages to prevent this form of bullying, and provide a feed of all changeset comments so that bullies can easily be spotted there.

Roadmap: A State of the Map for all communities worldwide 3 months ago

I'll buy you the free beer next time we're at the same conference!

Fix a Forest - experimental tiles from US Forest Service data 4 months ago

@RobJN: I've considered it but I'm not sure it's appropriate for this task - the amount of corrections to be done to the TIGER data is so vast that, barring a massive upswing in the number of people working on TIGER fixup, that sort of fine-grained approach is unlikely to work. I do wonder whether a P2 vector background layer might be useful, though, in helping to refine geometries.

@kucai: Yes, that's a useful tag and one which the Australians (understandably!) seem to like. It's a little problematic though in that it only addresses the road quality from a car driver's perspective, whereas a surface= tag can be used by cyclists, walkers, horseriders etc.

GORDON'S ALIVE 4 months ago

Essentially it now moves a node, rather than creating a new one, if the nearest point on the existing way happens to be near an existing node. Currently it's "within 15% of the distance to the next node", though I'd like to make that distance-sensitive in due course.

Just getting started mapping my places 4 months ago

The iD repository is at if you'd like to take a look!

Potlatch 2: see two sets of imagery at once 4 months ago

On occasion P2 does serve as a training ground for new JOSM features! (MapCSS, parallelise, etc.)