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How can I inform OSM about a map discrepancy (error) so they can update the tiles? For instance if you look at Columbia, SC there is a very large lake called Lake Murray. At zoom level 10 and lower it displays fine. If you zoom in to any levels above 10, the lake disappears and the islands in the lake look like little ponds instead of being green land.

Here is a permalink to the area. This is level 10 which displays the lake, if you zoom in one more level it disappears:

What is the standard way to report issues like this and how long does it typically take to resolve them? (I understand I'm not the only one in the world providing discrepencies, but just curious how long the average turn around time is on issues like this).

asked 24 Apr '13, 16:14

Russ's gravatar image

accept rate: 0%

edited 25 Nov '13, 14:49

aseerel4c26's gravatar image

aseerel4c26 ♦

One great tool is OSM Inspector, a QA tool which includes checks for Multipolygon geometry. As you can see at this link (until it gets updated--I think I corrected the issue) there was a gap in the outer ring of the multipolygon for the lake. Once the tiles get re-rendered, and you refresh your view, it should show correctly.

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answered 24 Apr '13, 19:21

neuhausr's gravatar image

accept rate: 21%


This is awesome! How can I learn more about fixing problem areas? Is there some documentation that teaches about the xml structure? Do I need to do anything special to become a developer to make change sets?

(24 Apr '13, 19:53) Russ

Great questions! OSM Inspector and KeepRight ( are two of the best QA tools, IMO. You can find more on the wiki: Info on the xml format is also on the wiki: To make a changeset, you just need to go to, create a user account (sign up link in upper right), login, navigate to where you want to edit, click edit, and create, edit and tag features. Once you click Save, the editing application (default online is Potlatch 2) takes care of the xml, changeset, etc.

(26 Apr '13, 15:14) neuhausr

The lake and the islands are part of a multipolygon see A quick look at two islands and two sections of the perimeter reveals they were formed in 2010 so if it was displaying OK I suspect someone as broken the lake polygon. It as a lot of nodes and it needs someone with some skill and confidence to sort it, It was also probably made with data other than BING which was unavailable at the time, so it may well be improved by being mapped from Bing by somebody who as the necessary skills.You could ask the original Mapper.

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answered 24 Apr '13, 18:15

andy%20mackey's gravatar image

andy mackey
accept rate: 4%

Thank you for the information. How does an average API user (me) know who the original mapper is? Once we know who it is how do we know about contacting them? The multipolygon link was helpful and informative.

(24 Apr '13, 18:44) Russ

Actually with this understanding of multipolygons I think I know what the problem is. The problem is simply the color of the islands and the color of the lake are inverting at zoom > 10. Essentially the islands should be white, but they show blue, the water should show blue, but shows white. Perhaps this problem will be somewhat easy to solve!

(24 Apr '13, 18:46) Russ

In the potlatch2 editor you can find who mapped a way by highlighting it, then in the side box click on advanced at the bottom, then click on way number at top. and some details including the mapper will show.

(24 Apr '13, 21:05) andy mackey

(Although your original issue has already been solved, I wanted to give a general answer to the question of how to tell OSM about issues on the map)

The best way to tell OpenStreetMap about an area that is wrong is by fixing it your self. Anyone can create an account on and click the edit button and start improving the data. As the person who spotted the error, you are probably one of the best qualified to fix the issue with your knowledge about the problem and the local area. Once your changes are saved, they are immediately available to everyone who uses OSM data, so it is also the fastest way to ensure the issue gets resolved. (Although it might take a while for the tiles to get re-rendered).

However, despite the effort to improve the editing tools for new users, not everyone might feel comfortable (or currently have the time) to edit the data directly, especially for some of the more complex features (like multi-polygons or other relations). Therefore it is now possible to leave a note on the map for other users or mappers to see. If you zoom in to where there is an issue with the map you can click on "add a note" in the bottom right corner of the page. This allows you to add a note to mappers which will then hopefully see it and fix the issue. Remember, the more precise the note is located and the issue described, the easier it is for someone else to fix the issue and likely the faster it gets resolved.

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answered 24 Apr '13, 21:03

apmon's gravatar image

accept rate: 20%

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question asked: 24 Apr '13, 16:14

question was seen: 4,401 times

last updated: 25 Nov '13, 14:49

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum