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

accept rate: 28%

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Copying from non-free sources like Google Maps

This is a huge no-no. Because OpenStreetMap is an open-source project, it can only use data that are published as open-source. This means that OpenStreetMap can use:

Your own data

  • from GPS traces
  • from seeing places in real life
  • etc.

Data from freely available sources

  • certain local governments (always check)
  • other open-source projects
  • tracing freely available satellite imagery (Bing Maps is ok, Google Maps is not)
  • etc.

These data have licenses on their copyright that let anyone use and distribute it freely (sometimes with restrictions, for example, that any project that uses the data must also be open-source). Other data may have stricter licenses on their copyright that disallow anyone from using it, or force you to pay. Some may have licenses that allow free use, but not free redistribution, which is unusable for open-source projects like OpenStreetMap because we are redistributing the data. Freely available or open-source means that the data must be freely redistributable.

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answered 11 Aug '13, 22:40

Clorox's gravatar image

accept rate: 0%

edited 11 Aug '13, 22:44

I often find myself going to Google Earth to get better angles on hidden objects, looking at it for reference because of the higher quality at max zoom, or using Streetview. Is that considered "copying"? Its practically required considering how much I do detailed edits, that my edits are more detailed than even traditional micro-mapping.

(06 Jan '18, 22:42) Mxdanger

@Mxdanger yes, unfortunately we can't use Google Earth even for "reference".

(06 Jan '18, 22:44) SomeoneElse ♦

Forgetting to add any tags to newly created nodes and ways !

I think this is a result of a combination of users mistakingly believing that they had deleted the untagged way or node, they didn't know at all that they created the node or way, a

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answered 10 Jan '13, 15:42

skorasaurus's gravatar image

accept rate: 12%

iD unfortunately makes it way too easy to do this. Potlatch 2 also lets you commit an untagged way without any sort of warning (in fact when I was still switching from iD to Potlatch 2 just to add parallel ways, and then switching back to do the rest of a dualize, I took advantage of this). JOSM will at least warn you, but how many newbie editors use JOSM?

(15 Dec '14, 07:02) skquinn

Thinking that everything has to have a "name"

I'm guessing that this is is partially because the Potlatch 2 "simple" interface has field called "name" for most features, and it's tempting to fill it in with something like e.g. "Public Footpath".

Similarly, there are lots of ways with oneway=no set. In some cases this might be necessary, but in many I suspect it's a case of "filling in all the fields".

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answered 09 Jan '13, 22:28

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%

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

malenki's gravatar image

accept rate: 6%

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 ♦

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

cartinus's gravatar image

accept rate: 27%

Users are generally not faulty, they just trust what the common editors allow them to do without warning them.

Merging ways with distinct tags or not members of the same sets of relations should open a conflict resolution editor allowing to see the differences and accept merging tags, or reject it (notably for distinct relations, these relations need to be merged separately if needed, using the same checks on tags and sets of parent relations)

The same remak applies when splitting ways (here also the parent relations need to be all updated in their lists of members), but most often it is simple to repair if a relation is forgotten.

(24 Feb '17, 13:25) verdy_p

In JOSM, the set of parent relations is not automatically loaded for all ways when merging or splitting them: but JOSM still does not automatically download the parent relations. You have to do it just before merging/splitting ways, pressing CTRL+ALT+D.

However the data server frequently returns 5xx errors when looking for parents (this error isn't reported by dialog or notification on the screen: you see it only on the console, provided that JOSM is launched from a command line window to see it, or by enabling the console window in the Java config menu. Unfortunately, if you close that window, there's no way to reopen it. Suggest JOSM to add an panel to show what is sent to the std-output.

If the server returns an error, nothing happens in the editor, users may feel that all parents are loaded, when they are not. The work around (if you see this error), is to zoom in on a tiny area around the node of the way to split or connecting ways to merge, and then download all objects in that area: the OSM server does not fail downloading all parents of these ways, when it fails by querying only the lists of parents and loading them: this is still a bug/performance issue on OSM server!

(24 Feb '17, 13:28) verdy_p

In the ID editor, there's a separate old unsolved issue, which occurs when splitting ways that are members of relations: the newly created way is just added at an inaccurate position at end of the list of members, instead of being inserted immediately before or after (depending on the connection of the other end nodes with other members before or after that way).

This creates havoc in many relations that expect a correct ordering, and complicates a lot the reparations that could be done later when the geometry needs to be repaired (not just for closed rings in multipolygons, but as well for linear objects such as associatedStreets/rivers...).

ID should preserve the continuity of member ways as much as possible, and when splitting ways, it is evident that both parts should NEVER be separated in the list of members.

(24 Feb '17, 13:29) verdy_p

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

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%

Long distance routes (notably motorways or national/interstate/state/regional highways) have a common descriptive name, but the actual identification is their ref number. That ref may be placed on member ways, but individual ways of course keep their local name (notably streets in cities/towns/villages), as defined by the local administrative authority. Even if this is the same administrative authority that manages the whole route, it still has distinctive local names for sections, e.g. for circular highways around towns/cities.

(24 Feb '17, 13:34) verdy_p

By looking at the maps, very often for example residental areas are limited to go along the roads, even when area continues on the other side of road. Because areas have border lines, this adds unnecessary clutter to maps. Maps are easier to read when there is as little as possible unnecessary information.

So I suggest to combine multiple areas to one when they are side by side.

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answered 12 Aug '11, 21:54

PetriT's gravatar image

accept rate: 0%

This is a difficult one. Yes, you can combine areas if they are side by side and tagged identical. But having a road in between them means they are not side by side anymore. You may still combine landuse=residential, as the road is part of the residential area. You may not combine a lancover=grass, as a road clearly is not covered by grass.

(19 Aug '13, 15:47) Chaos99

One difficulty is when one side of the road is residential and the other side is commercial or industrial. There's no general rule bout if the road itself is residential or commercial/industrial, when it is both, so that road will be used directly to separate both.

Note also that parking amenities NEED to be connected to roads. When a parking is only connected on the side of the road (without necessarily hacing an internal service highway for a parking aisle), it is common to extend the parking up to the line of the highway.

(24 Feb '17, 13:48) verdy_p

Node sharing will then happen (it clutters less the map with too many nodes nearby when in fact any change on the topology of the road will also impact the topology of the parking. However, if there's a physical border separation between both (kerb, plantation) it's best to keep them separated using parallel lines, and joining only where the pavement connects the parking.

A remaining problem in ID is that you annot easily select alternate ways passing through the same nodes (there's still no CTRL+Click or Alt-Click to cycle the last selection, and still no way to select all objects using that segment or node, and no selection list where you can deselect the undesired objects, and still allow viewing what is in each object in the selection.

Such demixing is much easier to do in JOSM.

(24 Feb '17, 13:49) verdy_p

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

emj's gravatar image

accept rate: 15%

edited 09 May '11, 12:19


Aerial imagery offset

In my area almost all new users don’t know about aerial imagery (Bing) offset. So they start drawing new objects without offset imagery at all. Sometimes even worst, they start moving old objects. Then I have to communicate them and revert or fix their edits. And True_Offset will not really helpful, because it change to frequently in hill area. From my point of view we have to keep remind new users of any editors necessity to adjust imagery. Maybe we can keep mark in database for users who confirm that he knows about offset.

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answered 07 May '11, 23:20

Dmitry%20Terentiev's gravatar image

Dmitry Teren...
accept rate: 0%

edited 07 May '11, 23:22

Bing offsets are frequent in its satellite imagery (correct medium resolution but imagery is not rectified) : Africa, Russia, Canada, Latin America, most of Asia.

But in US and most of Europe, where high-resolution orthophotography is available, this is no longer a problem as most areas are covered (but there remains a few spots in Europe only covered by satellite, e.g. Corsica, Sardinia and Sicilia, most of Switzerland and Austria, a North-West sector in Germany near the Netherlands, and about one half of UK).

(27 Nov '12, 10:25) Verdy_p

I'd disagree that "this is no longer a problem" in Europe where aerial photography is available. Maybe 100m offsets are a thing of the past there, but imagery still needs aligning.

(27 Nov '12, 10:40) SomeoneElse ♦

Using non-descriptive changeset comments

It's helpful to know (especially on "big" changesets) exactly what was being changed. Comments such as "Fix Tags" and "Fixed Stuff" don't really help; always try to put something in there (even if it's just referring to where the changes were made).

(and in the interests of full disclosure - I can be as guilty as the next person of this "common mapping mistake")

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answered 07 Mar '11, 15:05

SomeoneElse's gravatar image

SomeoneElse ♦
accept rate: 16%


Yes, and it is also helpful to try to avoid "big" changesets, and make them small enough that the description is precisely referring to the actual changes made.

(07 Mar '11, 15:20) dieterdreist

sometimes with potlatch2 I start editing and save and give a description of the edit, then go on editing and the program doesn't ask me for a new description... so my second save inherits a description that isn't necessarily correct.

(05 Sep '11, 14:41) mariotomo

You can ask Potlatch 2 to close a changeset by pressing "c". Then the next time that you save, it'll ask you for a new changeset comment.

(05 Sep '11, 14:48) SomeoneElse ♦

In general I'd say this is not so much a "common mapping mistake" but more of a thing we'd like new users to "graduate" onto doing, once they're getting the hang of editing. I don't think it should be regarded as essential, or rude not to. I do always try to add a good comment. Techy people are very fastidious about this kind of thing, but it might take some new users a while to pick up the habit, and that's fine.

@miriotomo yes. I make the same mistake quite a lot when dipping into Potlatch editing. I know about the 'c' button, but tend to save by mistake expecting to be asked (like in JOSM)

(12 Jun '12, 16:20) Harry Wood

Thanks, C is new for me, but pressing it, costs time to save it. I usually feel lucky if the question is nt displayed. Ill improve myself.

(14 Aug '12, 23:17) Hendrikklaas

@SomeoneElse You might want to add "and creating changesets than span continents". It's exactly the same problem, as the following mappers can't see what has happened. It also completely breaks the history page of openstreetmap.org.

(19 Aug '13, 16:06) Chaos99
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question asked: 06 Oct '10, 15:01

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last updated: 06 Jun '18, 11:03

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