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I'm interested in identifying the most common mapping errors you stumble upon from other OSMers (or that you make yourself).

If we could list some of the most common mistakes then we could use that information to drive improvements that may help to prevent the same mistakes being made in the future (e.g. by clarifying the wiki documentation, modifying the editor UI, writing scripts to find the mistakes etc).

This is obviously a very subjective question, but hopefully some people may find the answers useful. Please try to stick to definite actual errors, rather than simple differences of opinion.

This question is marked "community wiki".

asked 06 Oct '10, 15:01

GrahamS's gravatar image

GrahamS
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Not being explicit with topology. E.g. intersections / junctions are often not mapped in a way that makes it clear which way is the one discharged into the other (they seem equally important from the mapping, the form of the junction is not mapped). Topology is also a matter when it comes to the limitations of GPS accuracy: some users tend to believe the GPS unit more than their eyes: they map a feature on the other side of a road if the stored coordinates of the waypoint indicate this. Or they draw zigzig-lines where the road is perfectly straight.

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answered 27 Feb '11, 11:30

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edited 27 Feb '11, 15:10

1

Getting the topology to match what's on the ground is important to routers too - it makes the difference between "take the second exit from the roundabout" and "take the first exit".

(07 Mar '11, 12:49) SomeoneElse ♦

What's the correct way to tag which way is discharged into the other?

(24 Nov '12, 04:14) nicolas17

you do it geometrically, if it is not clear maybe it really isn't clear in the particular situation.

If you are after names or reference numbers you could see these as well, but in some special cases the name (maybe even the ref) don't follow the "main flow". (e.g. could imagine a road intersection, where continuing leads to a higher road and the current ref turns into "another" road).

(24 Nov '12, 16:30) dieterdreist

But... there must be a standard?

First timers often think that there is one right way to do stuff, or that everyone maps everything in the same way, this is not the case. We strive to make things simpler, but there really is no way to make thousands of people map the same way, so there is always going to be more than one way to do it.

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answered 09 May '11, 12:18

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edited 09 May '11, 12:19

Combine two highways because they have the same name, ...

but the two ways actually have different tags or are not both members of the same relation.

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answered 14 Aug '12, 18:42

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cartinus
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Wrong Tagging

For example using highway=footway for ways that also allow bicycles. The correct tagging would be either highway=path or highway=footway with bicycle=yes.

The opposite is the use of highway=cycleway for ways sharing both cyclists and pedestrians, hence needing either an additional foot=yes or just highway=path (and optionally foot=designated and bicycle=designated depending on the actual purpose).

These mistakes are quite common. Also see the wiki on access restrictions on different kinds of ways. They may differ from country to country.

For mistakes like unconnected ways, there exist several quality assurance tools such as keep right which report ways that are very close to each other, but unconnected, as well as many other common mistakes.

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answered 06 Oct '10, 16:24

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edited 06 Oct '10, 16:58

GrahamS's gravatar image

GrahamS
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2

About the only place I can think of where highway=footway would be appropriate for something that allows bicycles is the edge case of mapping a sidewalk in one of the rare areas (in North America at least) where operating such a vehicle on the sidewalk is OK.

(23 Feb '11, 22:25) Paul Johnson
2

The correct tagging would be either ...

This is frustrating - why are both possible? Is one more correct than the other?

(24 May '11, 21:58) jezmck

Mappers can tag what they like - depending on your point of view it's either the great weakness or the great strength of the project.

For more on highway=path vs highway=footway/cycleway search the mailing lists (if you're suffering from insomnia)

(25 May '11, 01:19) SomeoneElse ♦

JOSM Boundaries

In JOSM I once made the mistake of downloading an area then subsequently editing outside that area, without realising it was outside the extents of my downloaded region. So I ended up adding objects that were already there, but I didn't see them as I hadn't downloaded that area. I quickly found "Draw boundaries of download data" under the Preferences>Display>OSM Data and turned it on. No more of such problems. I think that from a usability point of view, it should be enabled by default.

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answered 07 Oct '10, 09:33

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edited 07 Oct '10, 09:48

GrahamS's gravatar image

GrahamS
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4

Fortunately, this is enabled by default.

(23 Feb '11, 22:24) Paul Johnson

Oh, that's right, it is. My mistake. I must have forgotten that early on I disabled it so I could see the pretty slippy map background clearly.

(05 Mar '11, 22:45) aharvey

Thinking that ways that are part of $longdistanceroute are actually called $longdistanceroute

In the UK at least, this usually isn't the case. I suspect that new mappers do it to get the name to appear on the main OSM Mapnik map, or because they haven't yet figured out how relations work.

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answered 05 Sep '11, 11:07

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Using search-and-replace to do small 'mass edits'

New users tend to use the search-and-replace function of editors to do 'corrections' to a massive amount of nodes or ways in their area when they believe they found an 'error' of some kind.

Not mentioning here if the 'error' really is one or not (new users might have trouble understanding all the tagging schemes used in OSM), the mere application of such changes in an automated manner often destroys more valuable data than it fixes. This is also regularly used to fill in perceived "blanks", even if those blanks are left intentionally or are coverde by some kind of default.

Examples are

  • attaching addr:postcode or addr:city to all buildings in a region (overwriting manually set fringe cases where postal address doesn't match real location)
  • adding oneway=no to all highways which don't have oneway=yes
  • standardizing names of shops/food chains, even if there really are some that carry another name on their sign

This is often combined with the "leave no changeset comment" problem already mentioned.

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answered 19 Aug '13, 16:02

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In Africa highway mapping, track only goes to farmland.

So ruled in Highway_Tag_Africa.

"The road conditions in African countries do not always correspond to their economic and social role. A road typology should be based on the road importance and not on the surface or the visual appearance of a road."

This means, it may look like a track but, if it goes from a major road to a hamlet, it's an unclassified highway, except a 4x4 can't drive it because it wiggles too much (then it's a path). Ditto from hamlet to hamlet.

People new to Africa mapping always get this wrong.

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answered 13 Dec '14, 14:51

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That's not so different from other countries. The highway tag should be used to tag the road classification, not the road's look.

(13 Dec '14, 17:13) scai ♦

From potlatch (users) I often have to fix self intersecting ways. Mostly this is a way going back again or making a small loop on itself before it ends or goes on. Not sure if this is a bug in Potlatch or if the users don't use it correctly.

At 348 km ways with 39.8 k nodes I had to clear ~90 of this errors.

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answered 24 Nov '12, 15:35

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This is perhaps part of the same problem as the "unjoined ways" problem. If people see the standard map tiles on osm.org as the "output" of their mapping rather than the data itself, then they won't think that self-intersecting ways are wrong.

As with unjoined ways, it's an education thing - once people have been told what's correct, they're more likely to do it right!

(09 Jan '13, 22:16) SomeoneElse ♦

Deleting nodes whose tag's don't show up in Potlatch 2. I have seen situation where new users will "clean up" nodes whose tags are "Not recognised".

Hopefully this will be going away with the greater prominence of iD.

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answered 06 Jul '14, 13:58

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question asked: 06 Oct '10, 15:01

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